Aegopodium podagraria

Goutweed was apparently first brought to North America as an ornamental during the early stages of European settlement and was well established in the U.S. by 1863. In parts of Russia, the leaves are sometimes used as a salad ingredient and potherb in the spring.

Goutweed (Aegopodium podagraria), also known as bishop's-weed and snow-on-the-mountain, is an herbaceous perennial plant, one of several species of Aegopodium native to Europe and Asia. Most leaves are basal, with the leafstalk attached to an underground stem, or rhizome. The leaves are divided into three groups of three leaflets, making it "triternate." The leaflets are toothed and sometimes irregularly lobed. Foliage of the "wild" type is medium green in color; a commonly planted variegated form has bluish-green leaves with creamy white edges. Sometimes reversion back to solid green or a mixture of solid green and the lighter variegated pattern occurs within a patch.

Small, white, five-petaled flowers are produced in mid-summer. Flowers are arranged in flat-topped clusters (called compound umbels) and are held above the ground on a leafy stem up to about 3 feet tall. The seeds are small and elongate, similar in size and shape to carrot seeds, and ripen in late summer. In contrast to the dense foliage cover produced by goutweed, flowering shoots are uncommon in densely shaded areas.

The rhizomes of goutweed are long, white, and branching, superficially resembling those of quackgrass (Elytrigia repens, also known as Agropyron repens). Patches of goutweed typically form a dense canopy and can exclude most other herbaceous vegetation. Because of this, it is often used as a low-maintenance ground cover.

Goutweed is an aggressive invasive plant that forms dense patches, displaces native species, and greatly reduces species diversity in the ground layer. Goutweed patches inhibit the establishment of conifers and other native tree species as well. An ecologically versatile species, Goutweed is found in old gardens and flowerbeds, around shrubs and other plantings, and in a variety of other disturbed habitats such as felled forests, abandoned fields, and pastures. In Eurasia, goutweed is primarily a species of deciduous and southern boreal forests, and it expands aggressively in similar habitats in North America. Goutweed appears to do best on moist soil and in light to moderate shade, but is highly shade-tolerant and capable of invading closed-canopy forests.

Goutweed is currently known to occur in twenty-nine states in the mid-Atlantic, Northeast and Northwest (USDA PLANTS map) and is reported to be invasive in natural areas in Connecticut, Michigan, New Jersey, Pennsylvania, Vermont, and Wisconsin (WeedUS Database).

This perennial plant is 1-2½' tall, consisting of basal leaves and flowering stalks with alternate leaves. The stalks are light green and glabrous.  The basal and lower leaves are bipinnate with 6-9 leaflets, while the upper leaves are pinnate with 3 leaflets. When the leaves are bipinnate, they are ternately divided into 3 groups of leaflets (2 lateral groups & a terminal group); each group has 2-3 leaflets. The leaflets of basal and lower leaves are 2-3" long and 1¼-2" across; they are medium to dark green, more or less ovate in shape, serrate or doubly serrate along their margins, and hairless or nearly so. Some leaflets may be deeply cleft into two lobes. The leaflets of upper leaves are smaller in size and more narrow in shape (lanceolate or oblong-lanceolate), otherwise they are similar to the leaflets of the preceding leaves. The petioles of basal and lower leaves are 4-12" long, while the petioles of upper leaves are less than 4" long. These petioles are light green and hairless; the petioles of alternate leaves are sheathed at their bases. The petiolule (basal stalklet) of the terminal group of leaflets is 2-3" long, while the petiolules of the lateral groups of leaflets are about 1" long. In each group of leaflets, the lateral leaflets are sessile or nearly so, while the terminal leaflet has a secondary basal stalklet that is nearly sessile to 1" long. The stalks terminate in compound umbels of flowers about 1½-3½" across that are flat-topped. Each compound umbel is divided into 10-20 umbellets, while each umbellet is divided into 10-25 flowers. The compound umbels lack floral bracts and the umbellets lack floral bractlets. Individual flowers are about 1/8" across, consisting of 5 white petals with incurved tips and an inferior ovary with a pair of styles. The peduncles of the compound umbels are 3-6" long, light green, glabrous, angular, and grooved. The pedicels of individual flowers are about ¼" in length, light green,  and glabrous. The blooming period occurs from late spring to mid-summer, lasting about 1 month. The flowers are replaced by ovoid-oblongoid fruits that are ridged and somewhat flattened; they are about 1/8" long and release their seeds at maturity during the autumn. The root system is fibrous and rhizomatous. Goutweed often forms clonal colonies from the spreading rhizomes.

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

More info for the term: invasive species

Goutweed was introduced in North America from Europe [82]. In the United States, goutweed occurs from Maine south to South Carolina and west to Minnesota and Missouri. It also occurs in the Pacific Northwest from Montana to Washington and Oregon. It occurs in all the Canadian provinces excepting Newfoundland and Labrador, and Alberta. Plants Database provides a distributional map of goutweed.

Globally, goutweed occurs primarily in the northern hemisphere, particularly in Europe, Asia Minor ([28,36,58,92], reviews by [14,27]), and Russia (review by [27,63]). Goutweed's native distribution is unclear. It may have been introduced in England (review by [2]) and is considered a "weed" in the former Soviet Union, Germany, Finland (Holm 1979 cited in [14]), and Poland [44]. It is nonnative in North America [82] and Australia including Tasmania (reviews by [2,14]).

Goutweed is grown as an ornamental (reviews by [13,72]) and occasionally escapes cultivation ([28,58,71], review by [95]). Little information has been published on its rate and direction of spread in North America. Darlington (1859 cited in [50]) considered goutweed invasive in the eastern United States by 1859, but goutweed was still considered uncommon in New England in the early 1980s [76]. Subsequent reviews on invasive species in New England indicate that goutweed may be becoming more widespread in Vermont [91] and Massachusetts [55]. A flora from Nova Scotia indicates that goutweed was locally abundant and becoming common in North America by the late 1960s [74]. In the early 1970's Swink [82] described goutweed as an "occasional weed" in northern Illinois, and an Illinois flora states goutweed is infrequent and rarely escapes cultivation [58].

So far, Goutweed has rarely escaped from cultivation and become naturalized in Illinois. It has been found as an escaped plant in only a few counties of NE Illinois (see Distribution Map). Because of its aggressive nature, Goutweed may become more common in the future. It was introduced into North America from Eurasia as an ornamental plant. Habitats include deciduous woodlands (sandy & non-sandy), shaded ravines, woodland borders, cemeteries, roadsides, and waste areas. Cultivated forms of Goutweed include those with variegated and non-variegated leaves. However, wild specimens of Goutweed almost always have non-variegated leaves.

Goutweed is currently known to occur in twenty-nine states in the mid-Atlantic, Northeast and Northwest (USDA PLANTS map) and is reported to be invasive in natural areas in Connecticut, Michigan, New Jersey, Pennsylvania, Vermont, and Wisconsin (WeedUS Database).

Most of Europe and northern Asia, to eastern Siberia

Aegopodium podagraria var. variegatum Bailey:
United States (North America)

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.

Aegopodium podagraria L.:
Canada (North America)
United States (North America)

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.

More info for the terms: adventitious, hypocotyl, rhizome

This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [28,52,58,71,74,76,92]).

Aboveground: Goutweed is a perennial ([52,62], review by [15]) herb [52,56,59,79,92,95] with erect, hollow stems (review by [14]). One review from the upper Great Lakes region indicated that goutweed grows from 4 to 12 inches (10-30 cm) tall [15], but it may grow to as tall as about 3 feet (1 m) in the northeastern United States [28]. In the Netherlands, goutweed grows from 1.5 feet (.47 m) [39] to 3 feet (1 m) tall ([59], review by [14]). Individual compound leaves are 1 to 3 inches (3-8 cm) long ([28], review by [15]). They are typically variegated but are occasionally all green [79], especially on plants established from seed [92]. Goutweed's inflorescence is a compound umbel [71,76] 2 to 4.7 inches (6-12 cm) wide [28]. Its seeds are about 1.4 mm wide [31].

Belowground: Information pertaining to goutweed's belowground morphology comes primarily from Europe. Goutweed has an extensive root system [41] that includes a main root and lateral roots. During early development, adventitious thick storage roots and thin feeding roots emerge from the hypocotyl. Eventually, additional adventitious roots form at rhizome nodes (review by [27]).

Goutweed has horizontal rhizomes [52,56,92] that may transition to vertical shoots at the end of the growing season (review by [27]). Reports of goutweed's rhizome length vary from 2 to 118 inches (5-300 cm) ([41,56], review by [27]). One study indicated that rhizomes are about 2 mm in diameter [56]. Nothing specific had been reported on how deep goutweed's rhizomes are buried in the soil as of 2009, but one review indicated that goutweed has a "weak shallow rhizome system" [34]. "Total" rhizome length may shorten as connections between ramets decay (review by [27]).

Stand structure: Goutweed exhibits clonal growth [59,62,74] and spreads by producing ramets ([59], review by [27]). In Massachusetts, goutweed forms dense mats (review by [95]). In Russia, goutweed's spatial distribution is nonrandom, and populations grow in clusters, presumably because of goutweed's rhizomatous nature [54].

Goutweed, also known as bishop's-weed and snow-on-the-mountain, is an herbaceous perennial plant. It is one of several species of Aegopodium, native to Europe and Asia. Most leaves are basal, with the leafstalk attached to an underground stem, or rhizome. The leaves are divided into three groups of three leaflets, making it "triternate." The leaflets are toothed and sometimes irregularly lobed. Foliage of the "wild" type is medium green in color; a commonly planted variegated form has bluish-green leaves with creamy white edges. Sometimes reversion back to solid green or a mixture of solid green and the lighter variegated pattern occurs within a patch.

Small, white, five-petaled flowers are produced in mid-summer. Flowers are arranged in flat-topped clusters (called compound umbels) and are held above the ground on a leafy stem up to about 3 feet tall. The seeds are small and elongate, similar in size and shape to carrot seeds, and ripen in late summer. In contrast to the dense foliage cover produced by goutweed, flowering shoots are uncommon in densely shaded areas.

The rhizomes of goutweed are long, white, and branching, superficially resembling those of quackgrass (Elytrigia repens, also known as Agropyron repens). Patches of goutweed typically form a dense canopy and can exclude most other herbaceous vegetation. Because of this, it is often used as a low-maintenance ground cover.

More info for the terms: cover, litter

Information about site characteristics where goutweed is invasive in North America is limited (2009). Information on sites where goutweed occurs comes primarily from European studies.

Climate: Goutweed occurs in temperate climates (see General Distribution). In Europe, mean precipitation on sites where goutweed occurred ranged from 19.5 [70] to 32.8 [26] inches (495-832 mm). Mean annual temperature was typically around 44 °F (7 °C), except where goutweed occurred in central Sweden, where average annual temperatures were as low as 42 °F (5.6 °C) [59].

Elevation: As of this writing (2009) no information is available on goutweed's elevational distribution in North America. Publications from Europe indicate that goutweed occurs at altitudes from 31 feet (10 m) [90] to nearly 3,488 feet (1,063 m) [33,45]. In one study from Sweden, goutweed was most common at altitudes from 1,030 to 1,120 feet (315-340 m) [33].

General habitat and moisture: Available evidence suggests that goutweed prefers moist conditions and may tolerate saturated soils. In the northeastern United States, goutweed is associated with moist sites [28]. In the upper Great Lakes region goutweed occurs on moist, well-drained soils [15]. In Australia, goutweed growth is "most prolific" in moist conditions and semishade (review by [14]). One review indicated that goutweed survives "very wet" conditions [72], and in Sweden, goutweed occurred on a site that was regularly flooded by an adjacent stream [33].

Leuschner and Lendzion [49] investigated microhabitat conditions for various herbaceous species in a beech forest in Germany and speculated that goutweed's occurrence was most influenced by relatively low soil moisture. On sites where goutweed occurred (i.e., open and sheltered valley sites, shallow and steep north-facing slopes) moisture content ranged from 33.2% to 36.4%; moisture content ranged from 25.2% to 28.1% on sites where goutweed was absent (i.e., rapid drying south-facing slopes) [49].

Microclimate and soil variables at 6 sites in a beech forest in Germany from March to May [49]

Variable

Valley North-facing slopes South-facing slopes open sheltered shallow steep shallow steep Goutweed cover (%) 15-25 15-25 3-5 1-3 0 0 Temperature (°C) 13.1 11.4 12.1 12.7 15.3 16.2 Relative humidity (%) 69.3 89.4 76.5 74.4 64 59.6 Vapor pressure deficit of air (Pa) 527 153 363 385 669 750 Photosynthetic active radiation (µmol/m²/s) 451 434 305 339 470 508 Soil moisture (volume %) 34.7 36.4 36.1 33.2 28.1 25.2 pH 7.3 7.1 7.2 7.4 7.3 7.3

In North America, goutweed is associated with anthropogenically influenced habitats like roadsides and the sides of buildings [74,76]. In Canada, goutweed has escaped cultivation primarily to roadsides and "waste places" in southwestern British Columbia and from southern Manitoba to Nova Scotia [62,75]. Goutweed occurs in grasslands, forests, roadsides, "waste places", and gardens in the upper Great Lakes region [15] and in Michigan, it occurs on forest borders [92]. On 1 site in Illinois, it occurred in a shaded ravine [82]. In Connecticut, goutweed occurs in floodplains and on the edges of wildlands (review by [13]). In Vermont it occurs in riparian and upland forests (review by [91]), and in Massachusetts it occurs on uplands, wetlands, and on floodplains (review by [95]). In North Carolina and South Carolina, the all-green type of goutweed occurs on the edges of bogs [71].

Goutweed occurs on similar sites throughout Europe. It occurs in managed or abandoned grasslands [83,84] or in fields where mowing or grazing has occurred [26,65,66]. Its occurrence has been associated with gardens [6]. It occurs in wildlands, especially in open forests, forest edges [39,67,83,88], and riparian areas [83,88].

Substrate: In regions outside North America, goutweed is considered a nitrophilous species ([42,53,83,88], Ellenberg 1979 cited in [22]). Soil pH, however, may influence goutweed's distribution more than nitrogen concentrations [23,90].

Available evidence from Europe indicates that goutweed occurs in soil pH ranging from 3.1 [24] to 9 [94], but several publications indicate it is most commonly found in weakly acidic [23,24,33,61,66] to weakly basic soils ([49,102], Ellenberg and others 1992 cited in [89]). In Sweden, goutweed occurred in a forest on sites with soil pH from 4.0 to 7.0. Over a 30- to 35-year period, goutweed cover increased more rapidly on sites where pH was >6.5 than in more acidic soils [22]. In a greenhouse, goutweed occurred in soil pH ranging from 3.17 to 4.5 but was most frequent on soils in the higher portion of that range (less acidic) [23]. In Britain, goutweed's nitrogen uptake was greatest in soils of pH 7 [3]. Two publications from Europe indicate that goutweed occurs on limestone [49,93].

Information on other substrate characteristics associated with goutweed is patchy. In Belgium, goutweed occurred in a flat, low-lying forest on sandy loam and silty loam. A layer of sandy clay occurred at approximately a 3-foot (1 m) depth and impeded drainage [90]. In Sweden, goutweed occurred in soils covered with a thin layer of litter that persisted from autumn to spring and decomposed by summer. There was no or only a thin layer of humus below the litter layer [21].

More info for the terms: codominant, cover, forbs, hardwood

Little is known about goutweed's plant associates in North America, particularly where it may be most invasive. In Illinois [82] and the Northeast [28,76,91], goutweed occasionally occurs in wildlands. In Vermont, goutweed occurs in upland hardwood forests [91]. At one location in northern Illinois, goutweed occurred with boxelder (Acer negundo), slippery elm (U. rubra), black walnut (Juglans nigra), black raspberry (Rubus occidentalis), bristly greenbrier (Smilax tamnoides), great ragweed (Ambrosia trifida), eastern waterleaf (Hydrophyllum virginianum), and woodland lettuce (Lactuca floridana), and [82]. Based on its plant community associates in Europe, in North America goutweed may potentially occur in deciduous and coniferous woodland or forest communities and in plant communities with tall herbs.

Information from Europe indicates that goutweed most commonly occurs in deciduous woodlands and forests [21,24,53,67,101,102], especially in riparian areas [98]. It also occurs in shrublands, wetlands [46], and grasslands [26]. It typically occurs in plant communities characterized by tall herbs [83,84,98]. Goutweed sometimes dominates or codominates the herbaceous layer in plant communities and is a characteristic species for some plant communities outside of North America. In Sweden, it is a characteristic species for 2 plant community types, both dominated by buttercup (Ranunculaceae) species [67]. In Germany, there is a goutweed cover type that contains other tall herbs such as nettle (Urtica spp.) [83,84]. In the Czech Republic, goutweed dominated an abandoned grassland with tall grasses and forbs such as colonial bentgrass (Agrostis capillaris), meadow foxtail (Alopecurus pratensis), red fescue (Festuca rubra), and white bedstraw (Galium album) [26] and was codominant in a nitrophilous (species that prefer sites rich in nitrogen) plant community with stinging nettle (U. dioica) that occurs on anthropogenically altered sites (e.g., along roads, hedges, walls) [42]. In Estonia, goutweed dominates a wetland community type [46].
Throughout its European range, goutweed occurs with a mix of deciduous trees that include ash (Fraxinus spp.) [53,67,84,102], oak (Quercus spp.) [21,24,53,67,101,102], beech (Fagus spp.) [24,33,49,67], maple (Acer spp.) [33,84,101], and elm (Ulmus spp.) [33]. It also occurs in coniferous forests. In Norway, goutweed occurred at the edge of a spruce (Picea spp.) forest bordered by a meadow [32] and in Russia, it occurred in a Norway spruce forest (P. abies) with either European aspen (Populus tremula) or littleleaf linden (Tilia cordata) [54]. In much of its northern European range, goutweed occurs in woodlands and shrublands characterized by willow (Salix spp.) [20,77], birch (Betula spp.) [20,77,101], common filbert (Corylus avellana) [33,53,101,102], and alder (Alnus spp.) [20,33,45]. In Europe, goutweed occurs with various forbs and grasses including stinging nettle [6,33,83], Canada thistle (Cirsium arvense) [6,60], bedstraw (Galium spp.) [26,84], and quackgrass (Elymus repens) [6,26,60].

So far, Goutweed has rarely escaped from cultivation and become naturalized in Illinois. It has been found as an escaped plant in only a few counties of NE Illinois (see Distribution Map). Because of its aggressive nature, Goutweed may become more common in the future. It was introduced into North America from Eurasia as an ornamental plant. Habitats include deciduous woodlands (sandy & non-sandy), shaded ravines, woodland borders, cemeteries, roadsides, and waste areas. Cultivated forms of Goutweed include those with variegated and non-variegated leaves. However, wild specimens of Goutweed almost always have non-variegated leaves.

Goutweed is an ecologically versatile species. It is found in old gardens and flowerbeds, around shrubs and other plantings, and in a variety of other disturbed habitats such as felled forests, abandoned fields, and pastures. In Eurasia, goutweed is primarily a species of deciduous and southern boreal forests, and it expands aggressively in similar habitats in North America. Goutweed appears to do best on moist soil and in light to moderate shade, but is highly shade-tolerant and capable of invading closed-canopy forests.

Floral-faunal relationships for this plant in North America are poorly understood. Müller (1873/1883) observed miscellaneous flies, beetles, wasps, small bees, and sawflies visiting the flowers for either nectar or pollen in Germany. Apparently the young foliage of Goutweed is considered edible to humans as it has been used in the Old World as a source of food and a medicinal herb.

Foodplant / sap sucker
Cavariella aegopodii sucks sap of live Aegopodium podagraria
Remarks: season: autumn-spring

Foodplant / feeds on
adult of Chrysolina oricalcia feeds on pollen of Aegopodium podagraria
Remarks: season: (3-)5-6(-10)
Other: uncertain

Foodplant / miner
larva of Cryptaciura rotundiventris mines leaf of Aegopodium podagraria

In Great Britain and/or Ireland:
Foodplant / parasite
cleistothecium of Erysiphe heraclei parasitises live Aegopodium podagraria

Foodplant / feeds on
larva of Liophloeus tessulatus feeds on root of Aegopodium podagraria

Foodplant / spot causer
mostly hypophyllous, immersed, scattered or congregated pycnidium of Phyllosticta coelomycetous anamorph of Mycosphaerella podagrariae causes spots on fading leaf of Aegopodium podagraria
Remarks: season: 6-7

Foodplant / open feeder
adult of Oomorphus concolor grazes on leaf of Aegopodium podagraria
Remarks: season: 4-2

Foodplant / open feeder
larva of Phaedon tumidulus grazes on live leaf of Aegopodium podagraria
Remarks: season: -late 8
Other: uncertain

Foodplant / miner
larva of Phytomyza obscurella mines leaf of Aegopodium podagraria
Other: sole host/prey

Foodplant / parasite
hypophyllous colony of sporangium of Plasmopara crustosa parasitises live leaf of Aegopodium podagraria

Foodplant / gall
embedded chlamydospore of Protomyces macrosporus causes gall of live stem of Aegopodium podagraria
Remarks: season: 3-10

Foodplant / gall
clustered telium of Puccinia aegopodii causes gall of leaf (nerve) of Aegopodium podagraria
Remarks: season: 4-8

More info for the terms: fire suppression, invasive species, prescribed fire, restoration

Preventing postfire establishment and spread: Although there may be potential for goutweed to establish either vegetatively or by seed after fire (see Fire adaptations), as of this writing specific information on preventing its postfire establishment and spread was lacking. In general, however, the best way to prevent the spread and establishment of invasive species is through early detection and eradication, careful monitoring and follow-up, and limiting dispersal of invasive plant seed into burned areas. General recommendations for preventing postfire establishment and spread of invasive plants include:

• Incorporate cost of weed prevention and management into fire rehabilitation plans
• Acquire restoration funding
• Include weed prevention education in fire training
• Minimize soil disturbance and vegetation removal during fire suppression and rehabilitation activities
• Minimize the use of retardants that may alter soil nutrient availability, such as those containing nitrogen and phosphorus
• Avoid areas dominated by high priority invasive plants when locating firelines, monitoring camps, staging areas, and helibases
• Clean equipment and vehicles prior to entering burned areas
• Regulate or prevent human and livestock entry into burned areas until desirable site vegetation has recovered sufficiently to resist invasion by undesirable vegetation
• Monitor burned areas and areas of significant disturbance or traffic from management activity
• Detect weeds early and eradicate before vegetative spread and/or seed dispersal
• Eradicate small patches and contain or control large infestations within or adjacent to the burned area
• Reestablish vegetation on bare ground as soon as possible
• Avoid use of fertilizers in postfire rehabilitation and restoration
• Use only certified weed-free seed mixes when revegetation is necessary

For more detailed information on these topics see the following publications: [5,10,29,86].

Use of prescribed fire as a control agent: As of this writing, no information was available on the use of prescribed fire to manage goutweed.

More info for the terms: cover, fuel

Fuels: As of this writing (2009) no information was available on goutweed's fuel characteristics.

FIRE REGIMES: With one exception, no published information was available at this time (2009) on North American plant communities where goutweed occurs, making it difficult to infer what FIRE REGIMES may be associated with goutweed. On one site in Illinois, goutweed occurred in a shaded ravine with box elder and slippery elm. FIRE REGIMES on this site may be similar to those described for wooded draws and ravines of the Great Plains. Surface or replacement fires may occur every 40 to 95 years, depending on moisture patterns and on the FIRE REGIMES of adjacent mixed-grass prairie and shrubland. Because native ungulates tend to concentrate in woody draws and ravines for food and cover, grazing may influence FIRE REGIMES and stand regeneration in these communities [48].

More info on this topic.

More info for the terms: cover, succession

Throughout its range, goutweed prefers partial shade ([18,28,79,88], reviews by [14,15]) but tolerates deep shade ([18,49,76,82], review by [55]) with up to 90% canopy cover [33].

Although goutweed has some attributes of early successional species (e.g., establishes on disturbed sites), available evidence suggests it is not typically associated with early succession. Goutweed has limited regeneration from seed and its seed dispersal may limit its ability to establish on new sites. In Canada, goutweed does not normally grow in full sun. Photosynthetic tissue of the all-green type may be harmed if exposed to full sunlight; however, tissue on variegated plants may not be affected [79]. One review from Massachusetts indicated that goutweed grows in full sunlight [55] but provided no further details on its growth potential on such sites. In a previously mowed meadow in Poland, goutweed did not establish until year 15 of a 20-year-study even though viable seeds were collected from the soil during previous years of the study. Goutweed established only after the meadow had transitioned to a willow scrub community with a high proportion of sedges (Carex spp.) [20]. In Germany, goutweed occurred only on the floor of a deciduous forest and not in a newly vegetated patch of ground with pioneer species [17].

Outside of North America, goutweed occurs in mid- [90,101] to late-successional stages ([77,101], De Keersmaeker and Muys 1995 cited in [89], Pysek 1977 cited in [70]), and based on its affinity for shade, it may occur in similar successional stages in North America. Goutweed's abundance tends to increase over time ([20,24,53], Pysek 1977 cited in [70]), and it may become more abundant in late succession. For example, goutweed was common in a 100- to 130-year-old German beech forest [49] and in Poland, it attained greatest cover on woodland sites in late succession [100].

Verheyen and Hermy [89] speculated that goutweed's occurrence may only be moderately correlated with forest age (r² =0.51). Other factors, such as habitat quality, pH [89], nitrogen availability [24], and distance to an undisturbed population of goutweed [89], may influence the distribution of goutweed more than forest age.

Population expansion of goutweed likely occurs primarily by vegetative means [6,101] from rhizomes (see Botanical description). Its vegetative reproduction has been described as "vigorous" [76]. It can produce new ramets from even small segments of rhizomes (review by [13]). Dense shading does not appear to restrict vegetative regeneration [101]. Two reviews recommend digging up goutweed's entire root system to control goutweed [2,15], but provided no details on the root sprouting capabilities of goutweed other than adding that the root system could be "rejuvenated" if not entirely removed [15].

More info for the term: rhizome

Goutweed seedlings are most likely to establish and survive under the forest canopy on well-lit sites where ground disturbance has occurred (e.g., animal digging) and on sites void of other plants (review by [27]). Because recruitment from seed is seldom seen in wild populations [59], seedling establishment may be rare. Even seedlings establishing in sunlight may die the same year they emerge because they compete poorly for water and nutrients compared to surrounding mature plants (review by [27]).

Gastuk [27] provides a detailed review of the process of goutweed development. Experiments in Japan indicate that goutweed cotyledons emerge in early spring after snowmelt and quickly develop primary rosette shoots [68]. A review from Europe indicates that during the next 5 to 7 years, lateral roots sprout from the main root, and horizontal rhizomes develop from axillary buds on the primary rosette shoot. Plants may reach reproductive stage 5 to 7 years after germination (review by [27]). Growth may be more rapid for clones that maintain rhizome connections, because connections allow for resource sharing between ramets in the sun and ramets in the shade [59]. Mature plants grow "vigorously" but eventually show signs of senescence and transition to a "post reproductive period" (review by [27]).

Some [74,79] consider goutweed plants with all-green foliage more "vigorous", spreading more rapidly than the variegated type. Higher photosynthetic rates in all-green plants may account for differences in growth. In a nursery, photosynthetic rates for variegated and all-green goutweed plants were comparable in full sun. However, in shade, photosynthetic rates for the all-green type were more than 50% higher than rates for the variegated type [79].

More info for the term: fresh

Seeds dispersed by goutweed plants in wildlands may have low germination rates [6], but in germination tests, goutweed seeds have shown moderate to high germination rates. In laboratory tests, 5% to 100% of goutweed seeds germinated after chilling at 41 °F (5 °C) [31,68,88].

At the time of seed dispersal, goutweed embryos are immature [25,68,88] and undergo a period of morphological and physiological dormancy before they germinate [68,88]. In Norway, 83% of goutweed seeds contained immature embryos, 15% contained endosperm but no embryos, and 2% were empty [25]. Before morphological dormancy can be broken, immature embryos must grow to full size; in the field, this process is triggered by cold temperatures in fall and early winter. An additional cold stratification period in the spring may be necessary to break physiological dormancy [88]. Several studies report that chilling of seeds induced goutweed germination. In the laboratory, exposure to temperatures of 41 °F (5 °C) for at least 16 weeks induced germination of goutweed seed [88]. In another study, no goutweed seeds germinated when fresh, but nearly all seeds germinated when exposed to 41 °F (5 °C) for 12 months [31]. A 3rd study [68] also induced goutweed germination at a temperature of 41 °F (5 °C) but obtained higher germination rates in a shorter time at 32 °F (0 °C). Vandelook and others [88] found that, once dormancy was broken, seeds germinated at constant and alternating temperatures ranging from 50 to 73 °F (10-23 °C).

More info for the terms: cover, density

Research pertaining to the longevity, density, and vertical distribution of goutweed seed in the soil seed bank is limited. Available evidence suggests that goutweed seeds form a seed bank, but seed longevity in the soil seed bank is unclear. In Denmark, 2 goutweed seedlings emerged from soil samples collected March to May at a depth of 3.9 inches (10 cm) [4]. In Poland, viable goutweed seed (collected to a 1.2-inch (3 cm) depth) occurred in an abandoned field, but goutweed did not occur in the aboveground vegetation until year 15 of the study [20]. Because goutweed does not likely have a long-range seed dispersal mechanism, it is possible goutweed established from soil-stored seed. In year 15, goutweed made up less than 10% of the aboveground vegetation cover [20]. Although goutweed's aboveground cover ranged from 11% to 50% over the next 5 years, no viable goutweed seeds were found in the soil seed bank after year 15 [20].

More info for the terms: monocarpic, polycarpic

In Switzerland [93], goutweed is insect pollinated, and it may be insect pollinated throughout its range. Goutweed emits a "strong" fragrance [9] and contains nectar on its nondeciduous floral parts (i.e., sepals, receptacle, gynoecium) [80]. It contains a number of volatile compounds that are suspected to influence insect-plant interactions [9,63], particularly those between bees and nectar-bearing plants [63]. In Sweden, pollinating beetles visited goutweed plants with fully developed flowers [19], although it is unclear whether beetles were acting as pollinators or just visiting the plants.

Goutweed has been described as both monocarpic [9] and polycarpic [8], but no details were given on how these determinations were made.

More info for the term: breeding system

• Pollination and breeding system
• Seed production
• Seed dispersal
• Seed banking
• Germination
• Seedling establishment and plant growth
• Vegetative regeneration

Although goutweed produces by seed and rhizomes (review by [15]), reproduction from seed may be rare [6,101], especially in wild populations [59].

More info on this topic.

More info for the term: geophyte

Raunkiaer [73] life form:
Geophyte

More info for the term: forb

Forb

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

Goutweed seed is dispersed by gravity [31,101], and a few goutweed seeds may be dispersed short distances by wind. In an experiment in the Netherlands, 12% of goutweed seeds disseminated when a ripe umbel was held up to a fan at wind speeds lower than 10 m/second. This compares with dissemination rates of 40% to 89% for other Apiaceae species tested. On a platform, goutweed seeds were dispersed up to 1.9 feet (0.58 m) at a wind speed of 3.7 m/second [39]. As of this writing (2009), no information is available on how animals may aid in the dispersal of goutweed seeds, but its seeds are ribbed [52,76], suggesting they might adhere to animal coats.

As of this writing (2009), no information is available on seed production in goutweed, but anecdotal evidence suggests goutweed may not be a prolific seed producer. Smirnova (review by [27]) indicated that goutweed only flowers and fruits on sunny sites. The flora of Nova Scotia [74] indicated that variegated goutweed plants rarely produce fruit.

More info on this topic.

More info for the term: phenology

Literature pertaining to goutweed's phenology is sparse and comes primarily from locations outside North America. A few North American floras have reported flowering periods for goutweed. In Illinois, goutweed flowers from May to August [58], and a review from the Great Lakes region states that goutweed blooms in June [15]. In the northeastern United States, goutweed flowers from July to August [76]. In Nova Scotia, goutweed flowers and fruits from June through July [74].

The remainder of information, primarily from Europe, suggests a phenology that begins in early spring with seedling emergence, stem growth, and leaf development and culminates with plant senescence in fall after the first frost. In a garden in Belgium, goutweed seedlings emerged throughout the spring, but most emergence occurred in March and April [88]. In an outdoor experiment in Japan, cotyledons emerged by late April [68]. In Europe, goutweed seeds germinated in May or early June, and cotyledons photosynthesized for 1 to 2 months before dying. Primary rosette shoots develop soon after the cotyledons die (review by [27]). In Italy, optimal stem growth of goutweed occurred after mid-April [1]. In Germany, goutweed leaves begin to develop in early spring but are not fully expanded until May, when anthesis begins. Leaves stay green until August, when they begin to yellow, but they do not die until the first frost [56]. In Australia, goutweed's flowering stems emerge in midsummer [2].

Goutweed is vigorous, rhizomatous perennial that spreads mainly by vegetative means. Patches increase in size through extension of the rhizome system. The flowers are pollinated by a wide variety of insects, including beetles, bees, and especially small flies. The seeds have no apparent morphological features that would facilitate dispersal. Goutweed seeds require cold stratification to germinate. While established goutweed plants are highly competitive in shaded environments, seedlings generally need recently disturbed soil and rather bright light in order to survive. Goutweed apparently does not form a long-lived seed bank, and the seeds generally germinate the year after ripening. Establishment of goutweed seedlings in the shade is rare. The primary vector for dispersal to new areas is humans. Most goutweed colonies spread to neighboring natural areas from intentional plantings, or by the dumping of yard waste that includes discarded rhizomes.

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: 9
Specimens with Barcodes: 20
Species With Barcodes: 1

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

More info for the terms: cover, invasive species, natural, nonnative species, prescribed fire, rhizome, shrub, tree

Impacts: Reports on goutweed's impacts in North America are limited and anecdotal in nature. Reviews have described goutweed as an "aggressive" invader in the upper Great Lakes region [15], Vermont [91], and Massachusetts [55]. In New England, goutweed persists in wildlands and is locally abundant (review by [13]). It is considered invasive in northern Illinois [37] and Massachusetts [95]. The most detailed information comes from Vermont, where goutweed threatens forested and open areas and dominates the ground layer in some areas. It is a particular threat to native vegetation in floodplain forests (review by [91]). Reports on goutweed's impacts in Canada vary. Catling [11] considers goutweed to be a high-priority nonnative species in need of control because of its "major impacts" to wildlands in Canada. Others [62,97] consider goutweed a minor threat to native plant communities in Canada; however, White [97] cautioned that it may become locally abundant.

Goutweed invades native ecosystems outside North America (review by [72]). In the United Kingdom, it is considered a nuisance species [16]. A review from Australia describes goutweed as the "worst" of garden weeds. It spreads rapidly under favorable growing conditions; a single plant can cover an area of 10 feet² (3 m²) in 1 year [2].

Control: Regardless of what control method is employed, control of goutweed may be complicated by its rhizomatous nature. Reviews indicate that sprouting occurs if any rhizomes remain [95].

All-green goutweed may be more persistent [74] and spread more rapidly than variegated goutweed (see Seedling establishment and plant growth), making the all-green type particularly difficult to control [79].

Fire: As of this writing (2009), no information was available on the use of prescribed fire to control this species.

Prevention: It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities [51,78] (e.g., avoid road building in wildlands [85]) and by monitoring several times each year [38]. Preventing the establishment and spread of goutweed may be facilitated by preventing its escape from cultivation. One review from the upper Great Lakes region recommended planting goutweed only on sites not adjacent to wildlands and in gardens where root spread can be restricted (e.g., between a sidewalk and a house) (review by [15]).

Cultural control: No information was available as of this writing (2009).

Physical or mechanical control: A couple of reviews recommend hand pulling, raking, and digging followed up by monitoring to control goutweed [2,95]; however, caution must be taken to remove the entire rhizome and root system (reviews by [2,15,95]). Removing flowers before seed set may help control goutweed (reviews by [2,15]). Because goutweed's starch reserves are typically depleted by spring, Meyer [56] speculated that goutweed might be killed if it was prevented from photosynthesizing in the spring. Tree and shrub cutting, root trenching [102], hay making [26], and cattle grazing [65,66] may also reduce goutweed cover, but these methods have been developed for agricultural fields and may not be applicable to wildlands.

Biological control: No information was available as of this writing (2009).

Chemical control: One review from the Great Lakes region indicated that glyphosate could be applied to goutweed's foliage in spring or summer [15], but details on its effectiveness where not provided.

Integrated management: Attempts to combine herbicide with landscape cloth, bark mulch, and hand weeding to control goutweed in a garden were unsuccessful because sprouting occurred from either rhizomes or root fragments left in the soil (review by [13]).

The preference is partial sun to light shade, moist to mesic conditions, and soil containing loam, clay-loam, or sandy loam. This plant has few problems with either insects or disease organisms. It can spread aggressively, particularly in locales with cool moist climates.

Goutweed is an aggressive invasive plant that forms dense patches, displaces native species, and greatly reduces species diversity in the ground layer. Goutweed patches inhibit the establishment of conifers and other native tree species as well.