Ailanthus altissima

Tree-of-heaven (Ailanthus altissima), also known ailanthus, Chinese sumac, and stinking shumac, is a deciduous tree in the mostly tropical Simaroubaceae family. Mature trees can reach 80 feet in height. Ailanthus has smooth stems with pale gray bark and twigs which are light chestnut brown, especially in the dormant season. Its large compound leaves are 1-4 feet in length, alternate, and composed of 10-41 smaller leaflets. Each leaflet has one or more glandular teeth along the lower margin. The leaf margins are otherwise entire or lacking teeth. Ailanthus is a dioecious (“two houses”) plant meaning that male and female flowers occur on separate plants. Flowers occur in large terminal clusters and are small and pale yellow to greenish. Flat, twisted, winged fruits each containing a single central seed are produced on female trees in late summer to early fall and may remain on the trees for long periods of time. The wood of ailanthus is soft, weak, coarse-grained, and creamy white to light brown in color. All parts of the tree, especially the leaves and flowers, have a nutty or burned nut odor.

Tree-of-heaven is a fast-growing tree and a prolific seeder that can take over sites, replacing native plants and forming dense thickets. Ailanthus also produces chemicals that prevent the establishment of other plant species nearby. Its root system may be extensive and has been known to cause damage to sewers and foundations.

Tree-of-heaven is a common tree in disturbed urban areas, where it sprouts up just about anywhere, including alleys, sidewalks, parking lots, and streets. For example, the book “A Tree Grows in Brooklyn,” by Betty Smith, is based on the tree-of-heaven. Away from cities, ailanthus is commonly seen in fields, and along roadsides, fencerows, woodland edges and forest openings. It occurs as seedlings that pop up by the hundreds in recently planted fields and as persistent thickets in rocky, untillable areas. In the United States, ailanthus is recognized to be a serious agricultural pest.

NOTE: It is important not to confuse native shrubs and trees with ailanthus. Native sumacs (Rhus) and trees like ash (Fraxinus), hickory (Carya), black walnut, butternut and pecan (Juglans) can be distinguished from tree-of-heaven by having completely serrated (toothed) leaf margins.

Tree-of-heaven was first introduced to America by a gardener in Philadelphia, PA, in 1784, and by 1840 was commonly available from nurseries. The species was also brought into California mainly by the Chinese who came to California during the goldrush in the mid-1800s. Today it is frequently found in abandoned mining sites there. The history of ailanthus in China is as old as the written language of the country.

Simaroubaceae -- Quassia family

    James H. Miller

    Ailanthus (Ailanthus altissima), also called  tree-of-heaven, Chinese sumac, paradise-tree, and copal-tree  (fig. 1), is an introduced species that has become widely  naturalized across the continent. Ailanthus has found an  extremely wide variety of places to establish itself, from urban  areas to reclaimed surface-mined lands. Its successful  reproduction on impoverished soils and in harsh environments  results from its ability to sprout from the roots and to seed  prolifically. Ailanthus is found as an upper-canopy component,  with varying frequency, in the eastern hardwood forests,  apparently spreading by sprouting after harvest disturbance.

Also called shumac, stinking sumac, Chinese sumac, and ailanthus, it was introduced by a Pennsylvania gardener in 1748 and was made available commercially by 1840. It gained some notoriety as the species featured in the book “A Tree Grows in Brooklyn,” by Betty Smith.

This tree is 40-80' at maturity, forming either single or multiple trunks and a relatively open ovoid crown on each trunk. Trunk bark is mottled light and dark gray; it has weak furrows and ridges that are irregular and fragmented. Branch bark is light gray with abundant lenticels (air pores), while young shoots are yellowish brown to green, relatively stout, and usually glabrous (sometimes temporarily pubescent). Alternate compound leaves about 1-3' long occur along the shoots; they are odd-pinnate (less often even-pinnate) with 11-35 leaflets. Individual leaflets are 3-6" long and 1-2" across; they are lanceolate with smooth margins, except near the base, where 1-2 pairs of blunt dentate teeth usually occur. The upper leaflet surface is dark green and glabrous, while the lower surface is pale to medium green and glabrous (or nearly so). The short petiolules (basal stalklets) of the leaflets are up to ½" in length. The petioles of the compound leaves are 3-6" long; their bases are swollen. Both the rachises and petioles are light green to red and glabrous (or nearly so). The crushed foliage of this tree has an odd scent, resembling a mixture of citrus and skunk-like odors. Tree-of-Heaven is dioecious, producing either all male (staminate) flowers or all female (pistillate) flowers on the same tree. These greenish yellow flowers are produced in panicles about 4-12" long. Male flowers are up to 1/3" across, consisting of a short calyx with 5 lobes, 5 narrow petals, and 10 fertile stamens. Female flowers are up to 1/3" across, consisting of a short calyx with 5 lobes, 5 narrow petals, 10 pseudo-stamens that are sterile, and 5 carpels with united styles. The male flowers, in particular, exude an unpleasant skunk-like odor. The blooming period occurs during mid- to late spring. While the male flowers wither away, the female flowers are replaced by single-seeded samaras that mature during the late summer or fall. Individual samaras are about 1½" long and 1/3" across; they are initially light green, but later become yellowish or reddish green, and finally become tan to brown. Each samara has two elongated membranous wings and a central seed; the wings are often slightly twisted. Individual seeds are about ¼" long, ovoid, and slightly flattened. The samaras are distributed by the wind or water. The root system is wide-spreading and relatively shallow; vegetative offshoots are sometimes produced from long underground runners.

More info for the term: mesic

Tree-of-heaven is native to Taiwan and central China, where it occurs from 22o to 34o N in latitude [304]. It is nonnative in North America, where it is distributed from British Columbia, southern Ontario and Quebec, and Maine south to Florida, Texas, southern California, and Mexico [105,158,208,297,328]. Tree-of-heaven spread in North America apparently followed 3 introductions from China. It was 1st imported to Pennsylvania in 1784 as an ornamental [71,93,139,287,288,312]. A 2nd introduction occurred in New York in 1820, where tree-of-heaven was again planted as an ornamental [62]. Both eastern introductions were from English stock imported from China. Tree-of-heaven was commercially available in eastern nurseries by 1840. The 3rd introduction was in California during the Gold Rush of the mid-1800s. Chinese immigrating to work in the gold fields and in construction of the transcontinental railroad brought tree-of-heaven to California, probably because of the tree's medicinal and cultural importance in their homeland (see Other Uses) [139,288]. Tree-of-heaven was first planted in Hawaii in 1924 [321]. Plants database provides a map of tree-of-heaven's distribution in the United States.

A century after the North American introductions, tree-of-heaven is still most common in its initial centers of distribution: the Northeast and California. In the eastern United States, it is most invasive from New England south to the mid-Atlantic states [93,233]. Tree-of-heaven is frequently found in the upper Midwest. It is weakly invasive in the middle and southern Great Plains [114,258]. It is uncommon south of North Carolina in the Southeast and in the South [82,233,324], but it is spreading in the South. By a 2008 estimate, tree-of-heaven was present in over 214,000 acres (86,600 ha) of southern forests [208]. In the West, tree-of-heaven is common throughout much of California and is locally common in Oregon and Washington [93,137]. In California, it is invasive in the Bay Area, the Central Valley, and in foothill counties with a history of gold mining [139,153]. It grows along waterways in the Pacific Northwest, including banks of the Snake and Columbia rivers [137]. In the Southwest it invades riparian zones and mesic canyons [287].

Tree-of-heaven has established in temperate climates throughout the world. Its earliest introductions may have been in Japan and Korea, where it is probably not native [191]. It was introduced in Europe in the 1700s and has become widespread there [86,163,288]. Using seed from European trees, introductions in Argentina, Australia, and Africa followed [139,140]. Kowarik [172] views human settlements as centers of distribution for tree-of-heaven, with roads providing the migration routes.

The non-native Tree-of-Heaven is native to China. It was introduced into the United States as an easy-to-grow landscape tree. It is occasional to locally common in most areas of Illinois, except the NW section of the state, where it is apparently uncommon (see Distribution Map). This tree is invasive and it is undoubtedly still spreading into new areas. Habitats include woodland edges and openings, thickets, riverbanks, vacant lots, landfills and dumps, gravelly back alleys, areas along roads and railways, fence rows, and urban waste areas. This tree is more common in urban areas than rural or natural areas; it is especially common in impoverished and poorly maintained areas of cities, where it is sometimes cultivated as a yard tree. Tree-of-Heaven is a pioneer species that prefers areas with a history of disturbance.

Tree-of-heaven is occurs in many states across the continental U.S. and Hawaii and to date has been reported to be invasive in natural areas in 30 states (see map).

Central China

Tree of heaven is reported to be invasive in natural areas in 30 states across continental U.S. and Hawaii. It is highly adaptable to disturbance and a huge range of soil types and conditions, grows best in full sun and is tolerant of drought.

Northeastern and Central China and Taiwan

Ailanthus altissima var. altissima :
China (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Ailanthus altissima (Mill.) Swingle:
Canada (North America)
Chile (South America)
United States (North America)
China (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

All regions of China except Hainan, Heilongjiang, Jilin, Ningxia, Qinghai [widely cultivated and naturalized elsewhere].

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Global Range: Native to central China and widely planted, it now occurs in practically every state of the U.S. and from Canada to Argentina, and is also escaped in Europe. Distribution and abundance in native range not known.

The frequency of Ailanthus occurrences increases as one nears the cities. In neglected urban areas, Ailanthus grows "as trees close to buildings, as hedges, or as bushy aggregates along railroad tracks, highway embankments".

Distribution: Native in China, cultivated in temperate and subtropical regions of the world and often naturalized.

More info for the terms: density, perfect, ramet, tree

Botanical description: The following description of tree-of-heaven provides characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [71,104,105,135,199,317,324]). Billings and others [28] provide a key for identifying tree-of-heaven and other eastern trees in winter.

Tree-of-heaven is deciduous. It may reach 60 to 70 feet (18-21 m) in height, 80 feet (24 m) in crown width, and 20 feet (6 m) in trunk diameter at maturity [8,71,105,308]. The champion tree as of 2010 was in Virginia; it reached 55 feet (17 m) in height, 48 feet (15 m) in spread, and 20 feet in diameter [8]. Tree-of-heaven may be shrubby when suppressed beneath the canopy or pruned regularly [104]. It has smooth, thin bark and a straight bole. Branches are brittle and self-pruning [71,104,105,308]. There are 2 branch types: long and short shoots. Long shoots are sterile and may extend 18 feet (5 m), while short shoots bear flowers and rarely reach more than 18 inches (46 cm) long [63]. The large, malodorous leaves are pinnately compound, with prominent glands on the back of each leaflet. Leaflets range from 15 to 41 in number, and total leaf length may reach 3 feet (1 m) [71,104,105,308]. Leaf stipules have nectaries that excrete sugars [30].

Most flowers are unisexual, but some trees may have perfect flowers [328]. The inflorescence is a 4- to 7-inch (10-20 cm) long panicle with 6- to 8-mm long flowers. Staminate flowers have a strong odor that is objectionable to humans. Fruits are one-seeded, dry schizocarps with wings. They are 1 to 2 inches (2.5-5 cm) long and propeller-shaped, resembling maple (Acer spp.) fruits [71,104,135,136,147,149,250,317]. The fruits grow in clusters; a fruit cluster may contain hundreds of seeds [163]. Seeds average 0.2 × 1.0 inch (0.6 × 0.25 cm) in area [9] and 27 mg in mass [201].

Roots are shallow and wide-spread [211]. Young trees have a taproot and several large lateral roots [230,248,249], although the taproot may diminish with age [211]. Ramets do not have taproots. In dry, rocky soil or beneath pavement, tree-of-heaven grows long, horizontal roots that do not branch until reaching a more favorable substrate [230,248,249]. Roots near the trunk thicken with age, serving as storage organs. Deep roots send out smaller roots that grow near the soil surface; stem shoots generally sprout from these shallow roots. Most roots occur in the upper 18 inches (46 cm) of soil [211].

Stand structure: Tree-of-heaven typically occurs in clumps, although it may form rows along streams, roads, and fences, and occasionally it grows as widely spaced, single stems. Clumping can result from an even-aged seedling establishment or from clonal expansion through root sprouting [249]. Open-grown colonies may eventually become dense by sprouting. Davis [61] observed a half-acre (0.2 ha) stand in Kentucky that had 32 stems. Stands subject to infrequent control measures may develop into even-aged thickets [77,151]. Untreated stands self-thin, so the stand tends to become even-aged over time. Two years after tree-of-heaven harvest in Pennsylvania, density of tree-of-heaven sprouts averaged 17,860 two-year-old sprouts/acre (mean height=9 feet (3 m)), with 10,019 one-year-old sprouts/acre (mean height=2 feet (0.6 m)). After 3 years many of the sprouts had died, so dead stems were more common than live stems [151]. Sprouts volunteering in closed-canopy understories remain suppressed and few in number. For example, Hunter [148] reported scattered, single-stemmed trees-of-heaven—rather than thickets—in the understory of a mixed-evergreen forest in northern California. On the Jefferson National Forest, Virginia, tree-of-heaven had a clumped distribution on low-leave shelterwood sites and a random distribution on clearcuts and high-leave shelterwood sites [47].

    Over- and understory trees-of-heaven. Photo © John M. Randall, The Nature Conservancy.

There are few clues as to tree-of-heaven's original growth habit in China, where it is native. As valued ornamentals, mature trees-of-heaven in China are often pruned to aesthetically pleasing, single-stemmed forms, with sprouts harvested for firewood and medicinal uses [140,249].

Life span: Tree-of-heaven is typically short-lived, with life spans ranging from 30 to 70 years [85,163,211]. Cloning from root sprouts can extend ramet life hundreds of years [148]. Sprouts from the first tree-of-heaven in North America, planted in Philadelphia's Bartram Botanical Garden 1784, still existed at the turn of the 21st century [45].

Physiology: Tree-of-heaven has several physiological adaptations that probably aid in its establishment and spread. It appears to be allelopathic [64,184,190,206,209,217]. Chemical extracts from the leaves, bark, roots, and seeds have inhibited germination and growth of other plant species in the laboratory [129,130,131,184]. Allelopathic chemicals (ailanthone and other compounds identified in these sources: [9,10,64,206]) are concentrated in roots and in young trees, with young ramets producing more toxins than older trees [129,184].

Open-grown trees-of-heaven are highly efficient at photosynthesis [30,33,34,122,194,207] and store large quantities of photosynthate in stems and roots [30,33,34,194,207]. Foliar nectaries excrete photosynthates during growth and flower initiation [31]. A study in a Mediterranean region of Spain found that even after 5 years of once- or twice-yearly cuttings, leaves from new tree-of-heaven sprouts showed higher rates of stomatal conductance in spring than leaves of uncut trees-of-heaven. The authors conjectured that regulating stomatal conductance helps sprouting trees-of-heaven grow quickly [54].

Tree-of-heaven is drought tolerant [87]. In Nava-Constan and others' [54] experiment in Spain, trees-of-heaven showed more positive leaf water potentials than native flowering ashes (Fraxinus ornus). Conflicting information states tree-of-heaven is intolerant [108] or tolerant [18,87] of flooding. Further observations and field studies are needed to resolve this conflict.

Tree-of-heaven is highly tolerant of most industrial pollutants [207,253], although it is sensitive to ozone pollution [111]. In a highly polluted area of Armenia, tree-of-heaven showed the least damage and best growth of 8 urban tree species (Derojan 1958 cited in [93]).

Tree-of-heaven, also known ailanthus, Chinese sumac, and stinking shumac, is a deciduous tree in the mostly tropical quassia family. Mature trees can reach 80 feet in height. Ailanthus has smooth stems with pale gray bark and twigs which are light chestnut brown, especially in the dormant season. Its large compound leaves are 1-4 feet in length, alternate, and composed of 10-41 smaller leaflets. Each leaflet has one or more glandular teeth along the lower margin. The leaf margins are otherwise entire or lacking teeth. Ailanthus is a dioecious (“two houses”) plant meaning that male and female flowers occur on separate plants. Flowers occur in large terminal clusters and are small and pale yellow to greenish. Flat, twisted, winged fruits each containing a single central seed are produced on female trees in late summer to early fall and may remain on the trees for long periods of time. The wood of ailanthus is soft, weak, coarse-grained, and creamy white to light brown in color. All parts of the tree, especially the leaves and flowers, have a nutty or burned nut odor.

Look-alikes: It is important not to confuse native shrubs and trees with ailanthus. Native sumacs (Rhus) and trees like ash (Fraxinus), hickory (Carya), black walnut, butternut and pecan (Juglans) can be distinguished from tree-of-heaven by having completely serrated (toothed) leaf margins.

• Plant: deciduous tree that can reach 70 ft. in height; twigs with smooth, pale gray bark, and twigs that are light chestnut brown, especially in the dormant season; dioecious meaning plants are either male or female; wood soft, weak, coarse-grained and creamy white to light brown in color; leaves, stems and some flowers have a strong, unpleasant to offensive odor likened to cat urine or rotting peanuts or cashews.
• Leaves: alternate, large (1-4 ft. long), compound, with 11-25 smaller leaflets, each with one to several glandular teeth near the base.
• Flowers, fruits and seeds: large showy clusters of small yellowish-green flowers produced during June; in summer, flat, twisted, single-seeded winged fruits or samaras are produced on female trees and may remain on trees for long periods of time; individual trees may produce an estimated 325,000 seeds per year.
• Spreads: reproduces by seed and by vigorous re-sprouting, especially in response to injury such as breakage or cutting.
• Look-alikes: compound-leaved shrubs and trees like staghorn sumac (Rhus typhina), ash (Fraxinus sp.), black walnut (Juglans nigra), and hickory (Carya sp.). Sumac has fuzzy, reddish-brown stems and leaves; ash species have opposite leaves; ash, black walnut, hickory and sumac leaf margins are completely to mostly toothed; black walnuts have large green fruits.

Trees, deciduous, up to 20 m tall; bark smooth and straightly grained. Branches with pith, yellow or yellow-brown pubescent when young, then glabrescent. Leaves odd-pinnate, 40-60 cm; petiole 7-13 cm; leaflets 13-27, opposite or nearly so; blades ovate-lanceolate, abaxially dark green, adaxially gray-green, smelly when rubbed. Panicles 10-30 cm. Flowers light green; pedicel 1-2.5 mm. Sepals 5, imbricate, 0.5-1 mm. Petals 5, 2-2.5 mm, base hispid. Stamens 10; filaments densely hispid basally, longer than petals in males, shorter than petals in females; anthers oblong, ca. 1 mm. Carpels 5; styles connate; stigmas 5-lobed. Samarium oblong, 3-4.5 × 1-1.2 cm. Seed in middle of wing, flat-globose. Fl. Apr-May, fr. Aug-Oct.

A large polygamous tree, upto 30 m high or more. Leaves large, 30-40 cm or more long. Leaflets upto 12 cm long, 2.5-4 cm broad, alternate, ovate-lanceolate, usually cordate at base, glabrous except the veins and midrib near the base, with 2-4 coarse teeth, each with a large gland beneath, margin almost entire. Petiolules 2-10 mm long; midrib prominent. Inflorescence panicle, 10-30 cm long. Bracts minute. Flowers c. 7.0 mm across. Calyx 5-lobed, unequal, sepals much smaller than petals, c. 1 mm long and 0.5 mm broad, valvate, joined at the base, margin serrulate, glabrous, ovate, acuminate. Petals spreading, c.3 x 1.5 mm, glabrous, hairy at the base. Staminate flower with 10 stamens, filaments c. 3 mm long, arising from the base of small 10- lobed disc; anthers 2-celled, dehiscing longitudinally. Pistillate flower: ovary deeply divided, ovule solitary in each cell. Fruit samara, 3.5-5 cm long, twisted at the top, light reddish brown.

More info for the terms: alliance, codominant, frequency

Tree-of-heaven is most common in urban areas [141]. It varies from a minor to important component of wildland vegetation in its North American range. Because of its scattered and disjunct distribution in North America, tree-of-heaven occurrence is not well documented for all plant communities where
it may occur [211]. The following descriptions are not restrictive, but they include plant communities where tree-of-heaven is a known invader.

In wildlands of the East and Midwest, tree-of-heaven is a common component in oak-hickory (Quercus-Carya spp.) and maple-birch-beech (Acer-Betula-Fagus spp.) forests [286]. It has infested hundreds of acres of oak-hickory forest in Shenandoah National Park, Virginia [195,303]. In eastern oak-hickory forests, tree-of-heaven is frequently associated with native black locust (Robinia pseudoacacia), an early-successional species, and nonnative Norway maple (Acer platanoides) and princesstree (Paulownia tomentosa) [45,46,117,227,249,314]. Other early-seral associates are black cherry (Prunus serotina), gray birch (Betula populifolia), sweetgum (Liquidambar styraciflua), and eastern redcedar (Juniperus virginiana) [117]. In oak-hickory woodlands of Gettysburg National Military Park, Pennsylvania, tree-of-heaven is associated with overstory with black oak (Q. velutina), red oak (Q. rubra), scarlet oak (Q. coccinea), mockernut hickory (C. tomentosa), and bitternut hickory (C. cordiformis). Nonnative invasives other than tree-of-heaven include the understory species Japanese barberry (Berberis thunbergii) and multiflora rose (Rosa multiflora). Late-successional native understory species include white ash (Fraxinus americana), black cherry, sassafras (Sassafras albidum), and boxelder (Acer negundo) [91]. In silver maple (Acer saccharinum)-white oak-red oak forests of Ohio, tree-of-heaven occurs with American elm (Ulmus americana), hickory, black locust, black walnut (Juglans nigra), and black cherry [67]. Tree-of-heaven stands have been observed in estuaries and freshwater marshes on the Atlantic seaboard. Tree-of-heaven dominated the overstory of the estuary at Jug Bay Wetlands Sanctuary, Maryland [164].
On the Georgia piedmont, tree-of-heaven is an important species in early-successional loblolly pine (Pinus taeda)-black oak-white oak forests. Native flowering dogwood (Cornus florida) and yellow-poplar (Liriodendron tulipifera) and nonnative Chinese privet (Ligustrum sinense) and winged elm
(U. alata) are common associated species [55].
Tree-of-heaven is most common in riparian, valley, and foothill communities of California. In riparian areas of southern California, tree-of-heaven frequently associates with Fremont cottonwood (Populus fremontii), California sycamore (Platanus racemosa), mule-fat (Baccharis
salicifolia), and poison-oak (Toxicodendron diversilobum). A 1990 to 1992 survey in Chino Hills State Park showed 15% frequency for tree-of-heaven, with
its geographic range and "vigor" increasing over the study period [162].
Tree-of-heaven is invasive in riparian zones of the Southwest [135,266,273,281]. In the middle Rio Grande Basin of New Mexico, it occurs in Fremont cottonwood-Rio Grande cottonwood-sandbar willow (P. deltoides var. wislizenii-Salix exigua) bosques along with nonnative, invasive Siberian elm (U. pumila) and white mulberry (Morus alba) [97]. Tree-of-heaven has invaded arroyos of the Sandia National Laboratory, New Mexico; nonnative Siberian elm and saltcedar (Tamarix ramosissima) and native Apache plume (Fallugia paradoxa) and fourwing saltbush (Atriplex canescens) are common associated species. On upland sites it occurs in Colorado pinyon-oneseed juniper (Pinus edulis-Juniperus monosperma) stands with Gambel oak (Quercus gambelii) and Siberian elm [203].
The following vegetation classifications describe plant communities in which tree-of-heaven is a dominant or indicator species:
Appalachians and Northeast

• tree-of-heaven forest alliance.
  Occurs in the Appalachians, the Piedmont, the Interior Low Plateau, eastern Kentucky, the Ozark and Ouachita mountains, and probably other areas in the northeastern
  United States. Common in disturbed areas, along roadsides, urban abandoned lands, and on limestone clifftops [223].

California

• locally dominant in riparian woodlands [204]

North Carolina

• dominant and indicator species in edge communities developing on logged sites near oak-loblolly pine forest [205]

Pennsylvania

• eastern white pine (Pinus strobiformis)-gray birch-tree-of-heaven shale scree slopes in the Delaware Water Gap National Recreation Area [241]
• occasional codominant in the black cherry-yellow-poplar-red maple (Acer rubrum)-white ash forest alliance of
  Valley Forge National Historical Park [246]
• modified successional forest at Allegheny Portage Railroad National Historic Site; this forest is dominated by "weedy, early successional
  species" [243]

Tennessee

• tree-of-heaven forest alliance in Great Smoky Mountains National Park [290]

Virginia

• successional mixed shrublands on the Petersburg National Battlefield [237] and in Richmond National Battlefield Park; sweetgum may codominate [238]
• locally dominant on disturbed calcareous forest on the Petersburg National Battlefield [237]
• successional tree-of-heaven forest in Colonial National Historical Park [236] and Appomattox Court House National Historical Park [234]

The non-native Tree-of-Heaven is native to China. It was introduced into the United States as an easy-to-grow landscape tree. It is occasional to locally common in most areas of Illinois, except the NW section of the state, where it is apparently uncommon (see Distribution Map). This tree is invasive and it is undoubtedly still spreading into new areas. Habitats include woodland edges and openings, thickets, riverbanks, vacant lots, landfills and dumps, gravelly back alleys, areas along roads and railways, fence rows, and urban waste areas. This tree is more common in urban areas than rural or natural areas; it is especially common in impoverished and poorly maintained areas of cities, where it is sometimes cultivated as a yard tree. Tree-of-Heaven is a pioneer species that prefers areas with a history of disturbance.

Tree-of-heaven is a common tree in disturbed urban areas, where it sprouts up just about anywhere, including alleys, sidewalks, parking lots, and streets. For example, the book “A Tree Grows in Brooklyn,” by Betty Smith, is based on the tree-of-heaven. Away from cities, ailanthus is commonly seen in fields, and along roadsides, fencerows, woodland edges and forest openings. It occurs as seedlings that pop up by the hundreds in recently planted fields and as persistent thickets in rocky, untillable areas. Nationally, ailanthus is recognized to be a serious agricultural pest.

Ailanthus grows best in loamy, moist soils but tolerates a wide  range of textures, stoniness, and pH. On the dry end of the  moisture spectrum it is drought hardy, and on the wet end it  cannot tolerate flooding. The species is widely recognized by the  urban populace since it frequently occupies and covers untended  areas in cities. The species' tolerance of harsh sites led to  testing for strip mine reclamation; a study in eastern Kentucky  found ailanthus better adapted to acid spoil than to calcareous  spoil and capable of growing on spoils with low to moderate  phosphorus (17). Soils on which ailanthus is most  commonly found are within the orders Ultisols, Inceptisols, and  Entisols.

Because of its wide distribution, ailanthus grows under a variety  of climatic conditions. Within the naturalized range of the  species, the climate can be temperate to subtropical and humid to  arid. In arid regions bordering the Great Plains, low  precipitation, from 360 to 610 mm (14 to 24 in) annually with 8  dry months, can be tolerated (7), whereas in humid localities in  the southern Appalachians rainfall can exceed 2290 mm (90 in)  annually (15). Annual maximum and minimum temperatures  are -9° and 36° C (15° and 97° F). Extreme  cold and prolonged snow cover restricts the elevational range to  the lower slopes of the Rocky Mountains and prolonged cold  temperatures have reportedly caused dieback, but resprouting  occurs (1,7).

● Found in many habitats; 100-2500 m.

Comments: Ailanthus is native to central China, where its history is as old as the written language of the country (Hu 1979). Little information is available on its ecology in China, although Hu (1979) reviews its cultural importance and value for wood products and medicine.

The species was apparently introduced into America by two different routes. The first route began with Pierre d'Incarville mistaking it for the lacquer tree in China and sending seeds to England around 1751 (Feret and Bryant 1974, Hu 1979). It was then introduced to America by a Philadelphia gardener in 1784 (Hu 1979). Because of its rapid growth and ability to grow in unfavorable conditions with little care, it became a common stock in eastern nurseries by 1840. The second route was through Chinese miners. During the days of the California gold rush, many Chinese miners brought ailanthus seeds with them as they settled in California, probably because of its medicinal and cultural importance to them.

Escaping from cultivation and quickly becoming established on both coasts, ailanthus has expanded its range considerably since its initial introductions. Specimens from the Harvard University Herbarium indicate that it "runs wild from Massachusetts...to Oregon ... and from Toronto, Canada ... to Argentina ..." (Hu 1979). In some localities ailanthus is so well established that it appears to be a part of the native flora (Little 1974).

In the eastern United States, the frequency of ailanthus occurrences increases as one nears the cities. In neglected urban areas, ailanthus grows "as trees close to buildings, as hedges, or as bushy aggregates along railroad tracks, highway embankments, walls at the ends of bridges and overpasses, or in cracks of sidewalks and along fences" (Hu 1979). Although it is usually found in disturbed areas, it occasionally spreads to undisturbed areas. Kowarik (1983) views human settlements as centers of its distribution and roads as migration routes.

In California ailanthus is widely naturalized in cismontane areas, especially around old dwellings and mining settlements (Munz and Keck 1973). It has become established in Pleasants Valley, Solano and Marin counties, Berkeley, Vacaville, Petaluma, San Andreas, Angel's Camp, Columbia, and in various places in the Sacramento Valley (Robbins et al. 1951).

The flowers are cross-pollinated by such insects as honeybees, other bees, beetles, and flies. Aside from seeking nectar and pollen from the flowers, very few insects feed on Tree-of-Heaven (at least in North America). The caterpillars of two moths, Atteva punctella (Ailanthus Webworm) and Samia cynthia (Ailanthus Silkworm), feed on the foliage of this tree. Some birds, like the Pine Grosbeak and White-Winged Crossbill, eat the seeds. There are scattered reports of limited browsing by deer on the foliage, and cattle sometimes browse on seedlings.

Ailanthus altissima (Tree-of-Heaven) introduced
(information is very limited; this observation is from Krombein et al.)

Bees (short-tongued)
Andrenidae (Panurginae): Calliopsis andreniformis sn (Kr)

Foodplant / spot causer
amphigenous colony of Mycocentrospora anamorph of Mycocentrospora acerina causes spots on live leaf of Ailanthus altissima

Because of ailanthus' scattered and disjunct occurrence over a  wide geographical range, a listing of associated species would  have little significance. Forest stands around cities are common  areas of invasion and establishment, but it may be an occasional  or minor component of forests following disturbance anywhere  within its naturalized range.

The species is relatively resistant to  insect predation (7). Three insect species are known to  feed on ailanthus foliage, however (2). Most noted of the  foliage feeders in the eastern range, especially in the South, is  the ailanthus web-worm (Atteva punctella). Larvae from  this insect feed on leaves enclosed in a frail, silken web.  Another larval feeder, imported from Asia, is the cynthia moth  (Samia cynthia). Ailanthus is the preferred host for this  insect, but wild cherry and plum can also become infested. The  Asiatic garden beetle (Maladera castanea) feeds on  numerous plants during night flights, including ailanthus.

    Although many fungi have been reported on the leaves and twigs of  ailanthus, the tree suffers little from disease, and its  pathology need rarely be a consideration in its culture (9). If  ailanthus can be said to be subject to a major disease it would  be Verticillium wilt (Verticillium albo-atrum). Many  trees were killed by this soil-borne wilt in Philadelphia in  1936. Shoestring root rot (Armillaria mellea) has been  reported in trees in New York (16).

    While this tree is rated moderately susceptible to Phymatotrichum  root rot (Phymatotrichum omnivorum) in Texas, it is  considered most satisfactory for planting in the southern parts  of Texas root rot belt (20,23).

    In Texas, seeds are eaten by a number of birds, including the pine  grosbeak and the crossbill (21). Occasional browsing by  deer has also been reported.

    Wind, snow, and hard freezes are damaging to tops of seedlings,  while mature trees are resistant to ice breakage (3). Resprouting  usually occurs, although repeated damage leads to a reduction in  seedling survival.

A variety of nectar- and pollen-feeding insects pollinate tree-of-heaven [5,227]. Although disagreeable to humans, the strong odor of the flowers attracts honey bees, flies, beetles, and other insects [5,211]. A study in suburban Chicago found large bee species were the primary pollinators; the bees visited both male and female trees. Flies, especially those attracted to fetid-smelling flowers, visited female trees-of-heaven often but were probably less efficient pollinators than the bees [5].

More info for the terms: bisexual, dioecious

Tree-of-heaven is mostly dioecious. Rarely, either bisexual trees or trees with both bisexual and unisexual flowers are found [71,104,148,211,328].

As with most species with wind-dispersed seed, tree-of-heaven appears to have a relatively uniform genetic system, with most diversity occurring among rather than within populations [94,249]. Because most North American tree-of-heaven populations originated from 3 introductions [71,139,288,312] (see General Distribution), they may be less genetically diverse than native Asian populations. A comparison of tree-of-heaven seedlings germinated from seed collections from 5 locations across the United States and 5 locations across China showed significant differences in height growth (P=0.01), root:shoot ratios (P=0.05), and leaf area (P=0.05) among seedlings from the United States and Chinese seedlings. Populations from the United States were taller, allocated relatively less biomass to roots than stems, and had greater leaf areas than Chinese populations [94]. In a common garden study comparing seedlings of populations within the United States, Feret and others [95] found California populations were significantly taller than eastern populations (P=0.01). Seed width and biomass were correlated with latitude (t=0.96), with northern populations having the widest, heaviest seeds. Feret [93] found some tree-of-heaven seed and seedling growth characteristics of provenances from the eastern United States and California appeared random, and they were not correlated (nor appeared best adapted) to site or geographic location. He reported significant differences between North American and Chinese tree-of-heaven provenances for seed and seedling characteristics. Contrary to expectations, there was no evidence of inbreeding depression in North American provenances compared to native Chinese provenances [93].

More info for the terms: root crown, root sprout, top-kill

Tree-of-heaven sprouts from the roots, root crown, and bole [93,145,163,185,211,275]. Although reproduction from seed is not rare, sprouting is its most common method of regeneration [163]. In Ithaca, New York, 58% of 1-year-old, excavated tree-of-heaven stems were root sprouts and 42% were seedlings [230]. Young trees that are cut to the root crown before bark becomes thick and corky often sprout from both the root crown and roots [163,275]. Bole damage promotes root, root crown, and bole sprouting [148,163]. Death or injury of the main stem usually results in prolific root sprouting [211]. Top-growth damage is not necessary for root sprouting to occur, however. Even as seedlings, trees-of-heaven produce horizontal roots capable of sprouting [45]. Except in the rose (Rosacea) [96,269] and willow (Salicaceae) (review by [327]) families, root sprouting without top damage is uncommon in woody species (reviews by [65,120]), but it is a powerful regeneration strategy for species employing it. Roots have more nutrient- and photosynthate-storing capacity than rhizomes, conferring better protection from aboveground disturbances such as fire [159,160] and show a stronger sprouting response after top-kill [65,120]. Tree-of-heaven sprouts are more likely to persist in low-light conditions, such as within a subcanopy, than are seedlings [85].

With tree-of-heaven's spreading root system, root sprouts may appear as far as 50 to 90 feet (15-27 m) from the parent stem [151,163,275]. During drought, tree-of-heaven translocates stem water into roots and begins stem die-back. Die-back may be extensive during extended droughts, but tree-of-heaven typically survives drought by sprouting from the roots when there is sufficient water to support new growth. Sprouting after frost die-back is common in tree-of-heaven's northern limits [93].

On the Himalayan foothills of India, trees-of-heaven with root crown girths between 12 and 16 inches (30 and 40 cm) showed greatest root sprout production following road construction. Trees in the largest-diameter class did not produce sprouts [179].

More info for the term: breeding system

Tree-of-heaven reproduces by sprouting and from seed [71,135,312]. Both methods are important to tree-of-heaven's reproductive success and invasiveness [87,249].

• Vegetative regeneration
• Breeding system
• Pollination
• Seed production
• Seed dispersal
• Seed banking
• Germination and seedling establishment
• Growth

More info on this topic.

More info for the terms: geophyte, phanerophyte

Raunkiaer [254] life form:
Phanerophyte
Geophyte

More info for the term: tree

Tree

Follow this link to the U.S. Forest Service Fire Effects Information Service to see a table with fire regime information that may be relevant to habitats in which this species occurs

Ailanthus is a successional  pioneer species, intolerant of shade (8). It competes  successfully in mixed stands of hardwoods throughout its range,  indicating that it was present at the start of stand  establishment.

    Allelopathic effects on over 35 species of hardwoods and 34  species of conifers have been demonstrated for water extracts of  ailanthus leaves (14). Only white ash (Fraxinus  americana) was not adversely affected. Germination and growth  of slashand Monterey pines (Pinus elliottii and  P radiata) were inhibited by scattering leaves of  ailanthus collected in June and July on the seed bed surface,  while leaves collected in October stimulated germination and  growth (22). Such studies point to a strong allelopathic  role for ailanthus in forest succession.

Ailanthus roots are shallow spreading,  often apparent at the soil surface, and roots near the trunk  thicken into enlarged storage structures. These large rounded  structures are assumed to be for water storage, contributing to  the drought hardiness of the species (4). There is a general  absence of a taproot with most roots present in the upper 46 cm  (18 in) of soil. Within this zone, the deeper roots send numerous  small roots to the surface. Adventitious shoots may arise from  any of the surface roots.

Although ailanthus is sensitive to frost damage during its early years (Adamik and Brauns 1957), 6-year-old trees have survived winters of -33 centigrades accompanied by high winds (Zelenin 1976). Although Koffer (1895) suggested that ailanthus was unable to withstand the prolonged dry seasons of the Midwest, Dubroca and Bory (1981) commented on the "drought resistance" of the species. Dry soils are probably more suitable for its growth than wet soils (Adamik and Brauns 1957).

Ailanthus does well on very poor soils. Adamik and Brauns (1957) cultivated the species on rather thin topsoil and it "thrives even on stony ground." The tree has been used in revegetating acid mine spoils, tolerating a pH of less than 4.1, soluble salt concentrations up to 0.25 mmhos/cm and phosphorus levels as low as 1.8 ppm (Plass 1975). The tolerance of ailanthus to soil salinity is a disputed point in the literature. Opinions range from "salty soils not suitable for growth" (Adamik and Brauns 1957) to ailanthus "growing well on very saline shell sands (Lavrinenko and Volkov 1973). Intermediate views are expressed by Brogowski et al. (1977), Semoradova and Materna (1982) and Zelenin (1976).

Ailanthus has been planted widely in urban areas because of its ability to tolerate atmospheric pollution. Its ability to adapt to "the dirt and smoke, the dust and drought of cities" was recognized nearly 100 years ago (Sargent 1888). More recently ailanthus has been observed to survive cement dust near cement and lime works (Klincsek 1976); it is moderately resistant to fumes produced by the coke and coal-tar industry (Kozyukina and Obraztsova 1971); its leaves absorb significant amounts of sulfur in areas of high traffic flow (Kim 1975); it can accumulate high levels of mercury in its tissues (Smith 1972); and it is somewhat resistant to ozone exposure (Davis et al. 1978).

Although ailanthus may suffer from root competition by other trees already established in an area (Cozzo 1972), usually it competes successfully with other plants (Cozzo 1972, Hu 1979) and is considered a "dangerous weed" in forest plantations (Magic 1974). A high degree of shade tolerance gives ailanthus a competitive edge over other plant species (Grime 1965). The production of toxic chemicals by ailanthus may also explain the success of this plant. An aqueous extract of ailanthus leaves has been shown to be toxic to 35 species of gymnosperms and 10 species of angiosperms (Mergen 1959). This may be important in limiting natural succession in ailanthus stands. The toxicity levels are highest in the leaves during the early part of the growing season and are maintained at high levels at least until October (Voigt and Mergen 1962).

More info on this topic.

More info for the terms: allelopathy, phenology, schizocarp, tree

Leaf expansion typically begins in early spring, with trees-of-heaven flowering and dispersing pollen in late spring [148,211]. Tree-of-heaven's seasonal development may sometimes be slower than associated woody species. On Nantucket Island, Massachusetts, tree-of-heaven was noted in a 1912 publication as "nearly naked" in early June, when other tree species had already leafed out [26]. Seed ripening begins in late summer and continues through fall. Schizocarps usually persist on female trees through winter [198,211], but they may disperse anytime from October through the next spring [211]. In New York, schizocarp clusters usually broke off in fall, while individual schizocarps often persisted until spring [230].

Tree-of-heaven phenology by state and region Area Event Time Arkansas flowers April-May fruits September-spring [147] California flowers May seeds ripen September-October [149] Carolinas flowers late May-early June fruits July-October [250] Florida flowers spring [324] Illinois flowers June-July [214] New Jersey seeds disperse October-early April;
about half disperse October-November [181] New Mexico flowers June-July [199] New York seeds germinate June seeds disperse October-April  [249] Texas flowers April-May fruits September-October[308] West Virginia flowers June-July [280] fruits late October-early April;
most dispersal October-November [180] Great Plains flowers mid-May-June [114] New England fruits mid-August-mid-October [267] Pacific Northwest flowers June-July [137] Southeast flowers May-July [82]

Seasonally, tree-of-heaven's allelopathic toxins are greatest in spring and decline as the growing season progresses [311]. See Impacts and Control for more information on allelopathy.

Fl. Per.: May-June Fr. Per.: July-August.

Tree-of-heaven reproduces both sexually (by seeds) and asexually through vegetative sprouting. Flowering occurs late in the spring. Ailanthus is dioecious, with male and female flowers on separate plants. The fruits, or samaras, occur in terminal clusters on female plants during the summer, and may persist on the tree through the winter. One study reports that an individual tree can produce as many as 325,000 seeds per year. Established trees also produce numerous suckers from the roots and resprout vigorously from cut stumps and root fragments.

The dense thickets of ailanthus  reproduction on disturbed soils of road cuts and city building  sites develop from root sprouts. Prolific root and stump  sprouting has discouraged use of ailanthus as an ornamental  species. After death or injury of the main stem the  wide-spreading shallow root system can give rise to an abundance  of sprouts. Sprouts have shown first-year height growth of 3 to 4  m (10 to 13 ft) (19). Thus, the species can be easily  propagated from either root cuttings or from coppicing.

Seeds, can be sown immediately upon  ripening or stratified until spring. In nurseries, seeds are  usually sown in the spring and seedlings transplanted early the  following spring. Germination is epigeal. Vigorous first-year  seedling growth of 1 to 2 m (3.3 to 6.6 ft) has been reported  (1,11). Average survival on 11 different plantings in  Indiana strip mines was 74 percent after the first growing  season and then decreased to 58 percent after the first winter  (5). This illustrates the winter damage and mortality frequently  reported (1,7).

    Because ailanthus is intolerant of shade, reproduction in natural  stands appears sparse and erratic except by sprouting.

Pollination occurs in  the spring and clusters of seed ripen from September to October.  The fruit is a samara with the seed in the center of a thin,  oblong wing, well adapted for wind dispersal. The ripe samaras  are greenish yellow or reddish brown. The seed usually persists  on the female tree through the winter, characterizing their  appearance, but can be dispersed any time from October to the  following spring. The species is a prolific seeder; the most  abundant seed production is from trees that are 12 to 20 years.

    After collection, seeds should be spread to air-dry. Number of  seeds per kilogram averages from 27,000 to 33,000 (12,235 to  14,970lb) and germination after cold stratification averages 65  to 85 percent (7,18). Seeds should be stored dry in  sealed containers. The recommended cold stratification is 50 C  (410 F) in moist sand for 60 days.

The yellowish-green flowers of  ailanthus appear from mid-April to July, south to north,  depending on latitude. The flowers are arranged in large panicles  at the ends of new shoots. A dioecious species, it bears male and  female flowers on different trees, with male trees producing  three to four times more flowers than are usually found on female  trees (11). Male flowers are more conspicuous than female  ones, emitting a disagreeable odor that attracts numerous  insects. The foul odor of the male flowers makes the tree less  favored for ornamental plantings in cities.

Ailanthus reproduces both sexually and asexually. Asexual reproduction is by vegetative sprouting from stumps or root portions (Hu 1979). Flowering occurs rather late in the spring (June). Ailanthus has the longest winter dormancy of all the trees in its native Chinese habitat (Hu 1979). Precocious flowering is not a rare occurrence in this species and has been observed in seedlings only 6 weeks after germination (Feret 1973).

Seeds ripen in large crowded clusters from September to October of the same year and may persist on the tree through the following winter (Little 1974, Hu 1979). An individual tree can produce 325,000 seeds per year which are easily wind-dispersed (Bory and Clair-Maczulajtys 1980). These seeds average over 30,000 per kilogram. This amount yields up to 6-7000 "usable plants" (Little 1974). Limited testing of ailanthus seeds indicate that they have dormant embryos, and that germination is benefited by stratification on moist sand for 60 days at 41 F (Little 1974).

Seedlings establish themselves rapidly by producing a well formed tap root in less than three months (Adamik and Brauns 1957). In more compacted soils these seedlings put forth long rope-like lateral roots to exploit a greater soil volume (Rabe and Bassuk 1984). Ailanthus grows quickly in full sunlight and averages a meter of growth in height per year for at least the first 4 years (Adamik and Brauns 1957). The trees may grow to 15-20 meters tall but have a rather short lifespan of less than 50 years (Adamik 1955).

Information on the growth and yield of  ailanthus in the United States at this time is lacking. Maximum  heights are often reported as 17 to 27 m (56 to 90 ft) and a  maximum d.b.h. as 100 cm (40 in) (10,12). A short-lived  species, it lives 30 to 50 years (20). On arid sites, 15  m (50 ft) or more of height growth can be reached in 25 years,  with a straight bole for 10 to 12 m (33 to 40 ft) (7). At a New  England location, trees reached a 10 to 15 m (33 to 49 ft) height  and 9 to 11 cm (3.7 to 4.3 in) d.b.h. in 30 years (11).

In the two centuries since its introduction into North America,  ailanthus has probably become differentiated into genetically  different subpopulations based on seed traits. Seed  characteristics of ailanthus have been identified as traits that  differentiate varieties and geographical strains. Ailanthus with  bright red samaras compared to the more common greenish yellow  has been named Ailanthus altissima var. erythrocarpa  (Carr.) Rehd. A study of 11 seed sources from California and  Eastern States found that seed width and weight were correlated  with latitude (6). Northern sources have wider, heavier seed than  the more southern sources.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 10
Specimens with Barcodes: 19
Species With Barcodes: 1

Tree-of-heaven is classified as a noxious or invasive plant on National Forest System lands [298,300] and in many states. Information on state-level noxious weed status of plants in the United States is available at Plants Database.

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: GNR - Not Yet Ranked

Reasons: Native to central China and widely planted, it now occurs in practically every state of the United States, and from Canada to Argentina, and is also escaped in Europe. Distribution and abundance in native range not known.

Global Short Term Trend: Increase of 10 to >25%

Comments: Trend in native range in China not known, but the species has become much more abundant globally in the past century.

Comments: Although only occasionally found in nondisturbed areas (Kowarik 1983), ailanthus is a prolific seed producer, grows rapidly and can successfully compete with the native vegetation. It produces toxins which prevent the establishment of other species (Mergen 1959). The root system is aggressive enough to cause damage to sewers and foundations (Hu 1979).

Ailanthus was not nominated by any specific preserve manager, but is recognized by TNC staff as an important exotic weed. A recent survey (2 March 1985) of CNPS members showed a wide distribution of this tree throughout California. Members of both the Mt. Lassen and Sequoia chapters consider it a major pest at low elevations. There are also reports of it growing in Santa Cruz, Riverside, San Bernardino, Los Angeles and San Diego counties.

Do not plant tree of heaven or spread its seeds when moving soil from infested areas. Before attempting control, ensure that you are not mistaking a native species like staghorn sumac, ash or walnut for tree of heaven. Elimination of tree of heaven requires diligence. Targeting large female trees for control will help reduce spread by seed. Because vegetative spread by male and female trees will continue to be a threat, elimination of all trees must be the long term goal. Systemic herbicides with active ingredients like glyphosate and triclopyr are most effective and can be applied to bark, cut stems or foliage.

Restoration Potential: Recovery potential is unknown.

Management Requirements: Weed control involves three fundamental objectives: prevention, eradication and control.

From a practical viewpoint, methods of weed management are commonly categorized under the following categories: physical, thermal, managerial, biological, and chemical (Watson 1977). Physical methods include both manual and mechanical methods. Thermal methods include both broadcast burning or spot treatment with a flame thrower. Managerial methods include the encouragement of competitive displacement by native plants and prescribed grazing. Biological control is usually interpreted as the introduction of insects or pathogens which are highly selective for a particular weed species. Chemical control includes both broadcast and spot application.

The most desirable approach is that of an integrated pest management plan. This involves the optimum use of all control strategies to control weeds. This approach is generally accepted as the most effective, economical, and environmentally sound long-term pest control strategy (Watson 1977). In cases where more than one control technique is used, the various techniques should be compatible with one another. Broadcast herbicide application, for example, may not work well with certain managerial techniques (i.e., plant competition).

PHYSICAL CONTROL. The two types of physical control methods discussed below, manual and mechanical, produce slash (i.e., cutting debris) that can be disposed of by several techniques. If cut before seeds are produced it may be piled and left for enhancement of wildlife habitat (i.e., cover for small mammals). Debris may be fed through a mechanical chipper and used as mulch during revegetation procedures. Care should be taken to prevent vegetative reproduction from cuttings. Burning the slash piles is also effective in disposing of slash.

MANUAL CONTROL. Manual methods use hand labor to remove undesirable vegetation. These methods are highly selective and permit weeds to be removed without damage to surrounding native vegetation.

Hand Pulling: Ailanthus is probably best controlled by manual removal of young seedlings. Seedlings are best pulled after a rain when the soil is loose. This facilitates removal of the rooting system, which may resprout if left in the ground. After the tap root has developed, this would be extremely difficult. Plants should be pulled as soon as they are large enough to grasp but before they produce seeds.

The Bradley Method is one sensible approach to manual control of weeds (Fuller and Barbe 1985). This method consists of hand weeding selected small areas of infestation in a specific sequence, starting with the best stands of native vegetation (those with the least extent of weed infestation) and working towards those stands with the worst weed infestation. Initially, weeds that occur singly or in small groups should be eliminated from the extreme edges of the infestation. The next areas to work on are those with a ratio of at least two natives to every weed. As the native plant stabilizes in each cleared area, work deeper into the center of the most dense weed patches. This method has great promise on nature reserves with low budgets and with sensitive plant populations. More detailed information is contained in Fuller and Barbe (1985).

Cutting: Manually operated tools such as brush cutters, power saws, axes, machetes, loppers and clippers can be used to cut ailanthus. This is an important step before many other methods are tried, as it removes the above-ground portion of the plant. For thickly growing, multi-stemmed shrubs and trees, access to the base of the plant may not only be difficult but dangerous where footing is uncertain.

Hand Digging: The removal of rootstocks by hand digging is a slow but sure way of destroying weeds which resprout from their roots. The work must be thorough to be effective as every piece of root that breaks off and remains in the soil may produce a new plant. Such a technique is only suitable for small infestations and around trees and shrubs where other methods are not practical.

Girdling: Girdling involves manually cutting away bark and cambial tissues around the trunks of undesirable trees such as ailanthus. This is a relatively inexpensive method and is done with an ordinary ax in the spring when the trees are actively growing. Hardwoods are known to resprout below the girdle unless the cut is treated with herbicides. Although it may be undesirable to leave standing dead trees in an area, this technique has been shown to reduce stump sprouting in live oaks, and may be a useful technique for controlling ailanthus.

MECHANICAL CONTROL. Mechanical methods use mechanized equipment to remove above ground vegetation. These methods are often non-selective in that all vegetation on a treated site is affected. Mechanical control is highly effective at controlling woody vegetation on gentle topography with few site obstacles such as rocks, stumps or logs. Most mechanical equipment is not safe to operate on slopes over 30 percent. It is also of limited use where soils are highly susceptible to compaction or erosion or where excessive soil moisture is present. Site obstacles such as rocks, stumps or logs also reduce efficiency.

Chopping, Cutting or Mowing: Saplings may be trimmed back by tractor-mounted mowers on even ground or by scythes on rough or stony ground. Unwanted vegetation can be removed faster and more economically in these ways than by manual means and with less soil disturbance than with scarification. However, these methods are non-selective weed eradication techniques. They reduce the potential for biological control through plant competition and open up new niches for undesirable vegetation. In addition, wildlife forage is eliminated.

Saplings usually require several cuttings before the underground parts exhaust their reserve food supply. If only a single cutting can be made, the best time is when the plants begin to flower. At this stage the reserve food supply in the roots has been nearly exhausted, and new seeds have not yet been produced. After cutting or chopping with mechanical equipment, ailanthus resprouts from root crowns in greater density if not treated with herbicides.

PRESCRIBED BURNING. A flame thrower or weed burner device can be used as a spot treatment to heat-girdle the lower stems of small trees. This technique has advantages of being less costly than basal and stem herbicide treatments and is suitable for use during wet weather and snow cover. Ailanthus resprouts after heat-girdling (Cozzo 1972).

MANAGERIAL CONTROL. In most cases ailanthus prevents the establishment of other native plants and must be initially removed. Following physical or thermal removal of mature plants, root crowns must be treated to prevent resprouting. Seedlings of native plant species usually cannot establish fast enough to compete with sprout growth from untreated stumps. Ailanthus is shade tolerant, so presumably can and will sprout under other plants.

Prescribed grazing: The continued removal of the tops of seedlings and resprouts by grazing animals prevents seed formation and also gradually weakens the underground parts. Grazing must be continued until the seedbank is eliminated, as the suppressed plants return quickly after livestock is removed and begin to dominate pastures again.

BIOLOGICAL CONTROL. The term "biological control" is used here to refer to the use of insects or pathogens to control weeds. The introduction of exotic natural enemies to control plants is a complex process and must be thoroughly researched before implementation to prevent biological disasters. Such tools are not normally suitable for preserve managers to implement.

Biological control of ailanthus has not been addressed to any extent beyond the anecdotal stage. No susceptibilty of ailanthus to parasites was found or noticed in Austrian nurseries (Adamik and Brauns 1957). French (1972) notes that the zonate leafspot (Cristulariella pyramidalis) causes defoliation of ailanthus in Florida. In India, Atteva fabricella is considered an ailanthus defoliator (Misra 1978) and Italian seedlings, weakened by cold, were weakly parasitized by the fungus Placosphaeria spp. (Magnani 1975).

Please notify the California Field office of The Nature Conservancy of any field observations in which a native insect or pathogen is seen to have detrimental effects on ailanthus. These reports will be used to update this Element Stewardship Abstract. Management techniques which may encourage the spread of species-specific agents may be desirable in controlling ailanthus.

CHEMICAL CONTROL. Methods of chemical control of ailanthus are poorly explored in the literature. Detailed information on herbicides in general is available in such publications as Weed Science Society of America (1983). The Weed Science Society reference gives specific or USDA (1984) information on nomenclature, chemical and physical properties of the pure chemical, use recommendations and precautions, physiological and biochemical behavior, behavior in or on soils and toxological properties for several hundred chemicals. Comprehensive coverage of this information will not be presented in this Element Stewardship Abstract. In applying herbicides it is recommended that a dye be used in the chemical mixture to mark the treated plants and thus minimize waste.

The following discussion highlights herbicide application methods which may be useful in controlling ailanthus. Herbicides may be applied non-selectively (i.e., broadcast applications) or selectively (i.e., spot applications). Both types of applications have advantages and disadvantages and will be discussed separately.

Broadcast Herbicide Application: In general, when using broadcast application methods, plants should be sprayed only when in full leaf. Results are poor prior to full leaf development. The best results have been obtained when plants are in the fruiting stage in late summer or early autumn (Mathews 1960).

Kolarvskij (1967) reports that 2,4-D can stop seedling growth in alianthus, and Sterrett et al. (1971) found that a mixture of 2- chloroethyl phosphoric acid and potassium iodide gives 80-100% defoliation of ailanthus within 3 weeks.

Spot Chemical Methods: Spot chemical methods consist of various techniques for manually applying herbicides to individual plants or small clumps of plants (such as stump resprouts). These methods are highly selective as only specific plants are treated. They are most efficient when the density of stems to be treated is low.

Jones and Stokes Associates (1984) reviewed a variety of spot chemical techniques. The following is an excerpt from this report, listing techniques in order of increasing possibility of herbicide exposure to the environment or to humans in the vicinity of treated plants.

1) Stem injection: Herbicides are injected into wounds or cuts in the stems or trunks of plants to be killed. The herbicide must penetrate to the cambial tissue and be water-soluble to be effective. The chemical is then translocated throughout the tree and can provide good root-kill, and thus prevents resprouting.

2) Cut stump treatment: Herbicides are directly applied to the cambial area around the edges of freshly cut stumps. Application must occur within 5-20 minutes of cutting to ensure effectiveness. McHenry (1985) suggests late spring as the best season to do this. In early spring sap may flow to the surface of the cut and rinse the chemical off. At other times of the year translocation is too poor to adequately distribute the chemical. Applications may be made with backpack sprayers, sprinkling cans, brush and pail, or squeeze bottles. This treatment is effective in killing root systems of sprouting hardwoods. Picloram should not be used for this technique as it is known to "flashback" through root grafts between treated and untreated plants and may damage the untreated individuals.

Tre-Hold, an asphalt based formulation containing 1% NAA ethylester has been used as a sprout retardant on ailanthus with varying degrees of effectiveness (Amchem Products 1967).

3) Basal/Stem sprays: High concentrations of herbicides in oil or other penetrating carriers are applied, using backpack sprayers, to the basal portion of stems to be killed. The oil carrier is necessary for the mixture to penetrate bark and enter the vascular system. This method gives good root kill, especially in the fall when vascular fluids are moving toward the roots. This method may be easier to use with small diameter stems than the two previous techniques.

4) Herbicide pellets: Pelletized or granular herbicides are scattered at the bases of unwanted plants. Subsequent rainfall dissolves the pellets and leaches the herbicide down to the root system. Optimal time for treatment is towards the end of the rainy season to prevent leaching beyond the root zone.

Management Programs: Tim Thomas (1985) has removed a small stand of ailanthus in the Santa Monica Mountains National Recreation Area, by pulling up young saplings and is currently monitoring the site to see if it resprouts.

Contact: Tim Thomas, Park Ranger, Santa Monica Mountains National Recreation Area 22900 Ventura Blvd. Woodland Hills, CA 91364, (213) 888-3440.

Management Research Needs: What types of undisturbed habitats does it invade? How do native species respond to ailanthus toxins, and how is recovery potential of an area previously occupied by ailanthus affected by these toxins? What is the chemical make-up of these toxins? What can be used to buffer the effects of the toxins so that understory native seedling growth is encouraged? At what age is the tap root so long that it precludes ailanthus removal by hand?

The preference is full or partial sun and moist to mesic conditions. Many kinds of soil are tolerated, including those containing loam, clay, rocky material, and sand. This tree tolerates most types of air pollution, although it is somewhat sensitive to ozone. It will also grow in contaminated ground that contains mercury and other toxic compounds. Growth and development are quite fast, although longevity of individual trees is short (usually about 50 years). The roots and foliage secrete a phytotoxic chemical, ailanthione, that inhabits the germination of seeds and stunts the growth of other species of plants. The wide-ranging roots can clog sewer lines and water pipes, and they have been known to penetrate street pavement and uplift the foundation of buildings.

Ailanthus's main importance remains in urban forestry, the  original purpose of its importation into the United States. The  species, tolerance of noxious emissions of gases and various  dusts assures its continued use for plantings in industrial  environments. Tolerance of poor soils and low soil moisture  dictates its selection for city plantings in arid climates as  well as shelterbelt plantings and on strip mine reclamation  projects, although its unfavorable traits (odor and root  sprouting) have decreased city plantings.

    Root sprouting into fields is also a problem in shelterbelt  plantings.

    Pollinating insects are attracted by the male flowers. Honey from  ailanthus has been reported as having an initial foul taste that  disappears with aging, resulting in an exceptionally good tasting  honey (13).

Comments: Valued for wood products and medicine

Tree-of-heaven is a fast-growing tree and a prolific seeder, that can take over sites, replacing native plants and forming dense thickets. Ailanthus also produces chemicals that prevent the establishment of other plant species nearby. Its root system may be extensive and has been known to cause damage to sewers and foundations.

A common tree in urban areas where it causes damage to sewers and structures, ailanthus poses a greater threat to agriculture and natural ecosystems. It is a vigorous growing tree and prolific seeder that establishes dense stands that push out natives. Tree of heaven contains chemicals, including ailanthone, that have been found to have strong allelopathic (herbicidal) affects on the growth of other plants which help it establish and spread.

Stewardship Overview: Ailanthus is a fast growing tree, a prolific seed producer, a persistant stump and root sprouter and an aggressive competitor with respect to the surrounding vegetation. It occurs primarily in disturbed areas, though it may invade undisturbed habitats. It was brought into California mainly by the Chinese who came to California during the goldrush in the 1890's, and frequently occurs in abandoned mining sites. Little work has been done on developing biological or chemical control methods. The most effective means of control may be to pull seedlings by hand before the tap root develops.

Species Impact: Although only occasionally found in nondisturbed areas (Kowarik 1983), Ailanthus is a prolific seed producer, grows rapidly and can successfully compete with the native vegetation. It produces toxins which prevent the establishment of other species (Mergen 1959). The root system is aggressive enough to cause damage to sewers and foundations (Hu 1979).

Ailanthus was not nominated by any specific preserve manager, but is recognized by TNC staff as an important exotic weed. A recent survey (2 March 1985) of CNPS members showed a wide distribution of this tree throughout California. Members of both the Mt. Lassen and Sequoia chapters consider it a major pest at low elevations. There are also reports of it growing in Santa Cruz, Riverside, San Bernardino, Los Angeles and San Diego counties.