More info for the terms: achene, cover, density, eruption, frequency, litter, marsh, monoecious, natural, presence, ramet, rhizome, series
Broadleaf cattail regenerates vegetatively through rhizome sprouts and sexually through seed germination [189].
Pollination: Female broadleaf cattail flowers mature before male flowers, making cross pollination possible or even likely [10,82].
Breeding system: Broadleaf cattail is monoecious [5,72]. Heterozygosity and polymorphism levels suggest extremely low genetic variation in broadleaf cattail stands, but genetic differentiation exists between stands; ramets within a site are more similar than those between sites. Researchers indicate that self pollination and clonal growth have increased the genetic homogeneity of stands while increasing genetic differences between sites. Increased genetic diversity of broadleaf cattail occurred at the most polluted sites along a transect from Louisville, Kentucky, to Circleville, Ohio. Researchers were not sure that pollution levels caused the genetic differences [109].
Seed production: When broadleaf cattail flowers, abundant seed production is possible. A review reports that typically more than half of pollinated flowers set seed [102]. In controlled conditions, broadleaf cattail grown from seed produced flowers early in the second year of growth. From 10 spikes that averaged 7 inches (18 cm) long, an average of over 222,000 seeds/spike was produced [238].
Many studies report poor flower production by broadleaf cattail. Sexual reproduction was rare in broadleaf cattail vegetation on the west side of Lawrence Lake in south-central Barry County, Michigan. Of 1,779 marked shoots studied over 3 years, only 3 flowered [45]. Degree of shading or depth of submergence may affect flowering. In broadleaf cattail monocultures in experimental ponds at the University of Arkansas, broadleaf cattail flowered only when roots were not submerged. Researchers suggested that self shading in dense stands may inhibit flowering [75]. In a manmade pond at Michigan's W. K. Kellogg Biological Station, the percentage of broadleaf cattail flowering in a single year in September varied with water level. Unsubmerged plants did not flower. When submerged under 6 inches (15 cm) of water, 33% flowered, and in 20 inches (50 cm) of water, 11% flowered [80]. Perhaps a water level influence on flowering is related to the nonflooded or barely flooded conditions necessary for successful seed germination. For additional information on this topic, see Germination.
Seed dispersal: Broadleaf cattail seeds are transported by wind, water, and substrate movement. Achenes have numerous long slender hairs at the base that allow fruits to float on water and blow in the wind [172], and some report that achenes split or burst when they contact water [92,98]. Broadleaf cattail produces abundant seeds [58]. A review describes the release of broadleaf cattail fruits from the spike. When fruits are dry, protective portions of the pistil shrivel and hairs on the achene spread. Spreading hairs produce pressure that bursts inflorescences and releases fruits into the air [102]. Wind dispersal distances of broadleaf cattail seeds collected in Hockessin, Delaware, were calculated from timed descents made indoors. Seed mass averaged 0.05 mg. Seeds fell at 0.13 m/s, and the estimated lateral distance traveled in a 10 km/h wind was 154 feet (46.9 m) [144].
Seeds are also dispersed through soil movement when mud clings to animals or people [47]. Seeds may also be transported with portions of broadleaf cattail clones that are torn by wind, water, ice, or animals [6]. Often seeds remain attached to spikes through the winter and are dispersed in the spring, and in some cases seeds fail to disperse. Apfelbaum [6] observed submerged cattail spikes with hundreds of nearby seedlings.
Seed banking: Broadleaf cattail produces a persistent seed bank. Although there are no reports of how long broadleaf cattail seed remains viable in the soil, its emergence from soils in late-seral forests that have long been unsuitable broadleaf cattail habitat suggests long-term persistence or long-distance dispersal. In Washington, a small percentage of field-collected broadleaf cattail seed germinated after being stored in a freshwater canal for 60 months [33]. While dense broadleaf cattail seedlings often emerged from sites where broadleaf cattail was important [126,210], there were exceptions [48,210]. Most of the studies below used the emergence method to determine the density of broadleaf cattail seed in the soil. This method requires, but rarely assures, that ideal broadleaf cattail germination conditions are provided.
Depth, season, and vegetation type: Broadleaf cattail emergence from soil collected in the Hamilton Marshes of New Jersey's Delaware River wetlands varied with season of collection, depth of burial, and vegetation type. Through field experiments, researchers determined that more than half of broadleaf cattail emergents came from persistent seed banks and not recent seed rain. The greatest number of broadleaf cattail seedlings (15,060/m²) emerged from the top 0.8 inch (2 cm) of soil collected in March from vegetation dominated by calamus (Acorus calamus) and broadleaf cattail. Soils collected in June from the same depth and vegetation type had 2,340/m² broadleaf cattail seedlings emerge. There were 5,060/m² and 2,150/m² broadleaf cattail seedlings in the top 0.8 inch of soils collected in March and June, respectively, in shrublands dominated by red maple (Acer rubrum), silky dogwood (Cornus amomum), and alder (Alnus spp.). Broadleaf cattail seedling emergence decreased with increasing soil depths, and no seedlings emerged from soil samples taken from depths greater than 5.9 inches (15 cm). More seedlings emerged on unprotected sites (53,000/m²) than on sites with seed rain excluded (38,700/m²). Although differences were not significant (P>0.05) [126], they suggest a persistent seed bank. For additional information on Leck and Simpson's [126] study, see Germination and Seedling establishment/growth.
High levels of seedlings or germinants are not always recovered from soils where broadleaf cattail is important. Few broadleaf cattails germinated from soils collected in eastern Tennessee mixed-deciduous forests. Soil samples collected in the spring from a site where broadleaf cattail frequency was 70% had 27±10 (SE) broadleaf cattail germinants. No seedlings germinated from summer-collected soils. From a site where broadleaf cattail frequency was 10%, there was only 1 germinant/m² from spring-collected soils [48].
Newly-colonized sites: Broadleaf cattail seed was recovered from new substrates resulting from the eruption of Mount St Helens. Seed banks develop soon after broadleaf cattail colonization [238]. In late September, soil samples were collected from newly-developed wetlands. No broadleaf cattail seedlings emerged from soil collected in wetlands where broadleaf cattail cover averaged 60%. In a wetland where broadleaf cattail cover averaged 90%, 126±145 (SD) seedlings/m² emerged from the top 2 inches (5 cm) of soil, and 1,088±1,609 seedlings/m² emerged from 2- to 4-inch (5-10 cm) depths. No broadleaf cattail seedlings emerged from soil samples that were not cold stratified. Researchers suspected that soil samples contained more broadleaf cattail seed than what emerged and that germination conditions were not ideal in the greenhouse [210].
Disturbed and late-seral forests: In south-central British Columbia, broadleaf cattail seeds emerged from undisturbed, 1-year-old "lightly burned", and 1-year-old clearcut Douglas-fir (Pseudotsuga menziesii) forests, although broadleaf cattail was not part of the existing vegetation. Broadleaf cattail seedlings emerged from soil samples collected from 5% of the quadrats in the undisturbed area, from 5% of lightly-burned quadrats, and from 2% of clearcut quadrats [195]. Few broadleaf cattail seedlings also emerged from the litter or top 0.8 inch (2 cm) of soil collected from 130- to 175-year-old mixed-conifer forests in eastern Oregon's Blue Mountains, although broadleaf cattail was not present in study plots or adjacent areas. Researchers suggested that broadleaf cattail seed survives in the soil until conditions are conducive to germination, allowing broadleaf cattail to rapidly occupy disturbed sites [202]. Low numbers of broadleaf cattail seedlings also emerged from soil collected in mature Douglas-fir and fir (Abies spp.) forests averaging 88 years or older in central Idaho [114].
Germination: Specific requirements necessary for broadleaf cattail germination are difficult to ascertain. Experimental studies indicate that light and warm temperatures are necessary for broadleaf cattail seed germination. However, studies involving flooding, leaf litter extract, and stratification effects on seed have produced conflicting results.
Broadleaf cattail seeds collected for 3 years from populations at 8,500 feet (2,600 m) elevation near Grand Lake, Colorado, failed to germinate. Researchers noted that broadleaf cattail had occupied the site for at least 12 years and that vegetative growth was vigorous [149]. Reasons for the variability in germination potential, requirements, and tolerances are unknown. Possibly broadleaf cattail seed viability is temporally, environmentally, ecotypically, and/or genotypically variable.
Cold stratification: As part of an extensive study of broadleaf cattail ecotypic population differences, McNaughton [147] found that broadleaf cattail seeds did not require a cold period before germinating, but the lowest temperature at which 50% germination occurred was lower in southern than northern populations. Broadleaf cattail seeds collected in soils from newly-developed wetlands on Mount St Helens only germinated in soils that were stratified (37 °F (3 °C)) for 12 weeks. No seedlings emerged in unstratified wetland soils [210].
Salinity: Choudhuri [27] found that broadleaf cattail germination percentages decreased with increasing salinity. No seeds germinated above 1 atm of osmotic pressure in natural salinity. For additional information on broadleaf cattail's tolerance of salt as a juvenile and adult plant, see Soil salinity.
Light, pH, temperature, oxygen, and ash: Broadleaf cattail seeds germinate best in warm temperatures and high light conditions [19,191,224]. Seeds germinate in acid, basic, or neutral pH conditions, and ash extracts have increased broadleaf cattail germination [178]. Reduced oxygen levels through the manipulation of gases in the air or through submersion have also increased broadleaf cattail germination success [191].
Broadleaf cattail seeds collected from North Bay Park on Ford Lake Reservoir shores in Washtenaw County, Michigan, germinated better in light than in dark conditions, better at 77 °F (25 °C) than at 68 °F (20 °C), and better when submerged than when exposed. Exposed seed germination, regardless of temperature or light exposure, ranged from 0.8% to 5%. Germination was best, 79.2%, when seeds were submerged, in the light, and kept at 77 °F (25 °C) [224].
Germination increased with increasing temperatures for broadleaf cattail seeds collected in May and October from Carlos Avery Wildlife Management Area, Minnesota. Maximum germination percentages occurred at the maximum temperature tested, 95 °F (35 °C). No seeds germinated at 50 °F (10 °C). Seeds exposed to cold temperatures before exposure to 95 °F (35 °C) temperatures had lower germination percentages than seeds kept at room temperature. Germination did not occur when seeds were exposed to low oxygen levels of 1.0 mg/L, and at least 10 hours of continuous red light was required for maximum germination. Researchers suggested that broadleaf cattail germination in the field would be most likely at the surface of saturated soils [19].
Optimum broadleaf cattail germination temperatures were 77 to 86 °F (25-30 °C), and seed crops responded differently to reduced and normal oxygen levels in studies conducted in Ontario. Germination rates were slower and percentages were reduced at 68 °F (20 °C) and 95 °F (35 °C). Seeds immersed in water germinated better than those kept moist. When moist seeds were exposed to reduced oxygen levels (2%), germination percentages equaled those of immersed seeds. Light exposure increased germination. The light intensity required for germination was low, but critical intensities varied with individual seeds. Seeds in full light had 99% germination. In containers wrapped with 3 layers of herbarium paper, germination was 97%, and when wrapped with tin foil, germination was 5%. Germination studies spanned many years, and differences were found among broadleaf cattail seed crops. Seeds collected in 4 of 7 years had increased germination in low oxygen environments, but 3 crops showed little to no apparent difference with oxygen levels changes [191].
Collection time affected the germination of broadleaf cattail seed collected in November and May in central Alberta. Less than 1% of fall-collected seeds germinated in light and distilled water, but 90% of seeds collected in May germinated. Germination in light (81-90%) was significantly higher than in the dark (15-73%, P<0.01). Germination in the dark increased when broadleaf cattail ash was added to distilled water. Germination was not affected by pH levels of 4, 7, or 12. Researchers suggested that high light levels and ash on burned sites may favor broadleaf cattail seed germination. Researchers also suggested that low humidity levels during seed storage may have affected viability [178], but spring collected seeds may have benefited from natural stratification.
Flooding: Many controlled experiments indicate that broadleaf cattail seeds germinate well in submerged or flooded conditions; however, field observations suggest regeneration from seed is restricted to nonflooded substrates [189]. Beule [16] indicated that field observations made in southeastern Wisconsin did not agree with laboratory reports of broadleaf seed germination in flooded conditions. Only once did Beule find broadleaf cattail seedlings in areas where germination may have occurred under shallow water. All other field observations suggested that germination was restricted to exposed substrates [16]. Differences between laboratory and field observations may relate to light requirements. The quality and murkiness of water in the field and water used in the laboratory were likely different, and associated vegetation cover in the field was not likely mimicked in laboratory studies.
Broadleaf cattail seeds collected near Huntley, Montana, germinated at very low percentages regardless of pH or temperature treatments. Only when seed coats were ruptured along the edge were high germination percentages achieved. Broadleaf cattail seeds with ruptured seed coats germinated under 30 inches (76 cm) of water and grew to the surface [238]. Broadleaf cattail germination percentages were greatest, about 43%, at 16 inches (40 cm) deep and lowest, approximately 16%, when unflooded at the Aquatic Environmental Research Facility in Lewisville, Texas. Germination percentages at 31-inch (80 cm) and 39-inch (100 cm) depths were about 25% [188].
Emergence of broadleaf cattail from reclaimed coal mine wetland soils in Perry County, Illinois, was better when samples were submerged in 0.8 inch (2 cm) of water than when kept moist [31]. Flooding soils collected from the Hamilton Marshes of New Jersey's Delaware River wetlands with 1.2 to 1.6 inches (3-4 cm) of water did not significantly affect broadleaf cattail germination (P>0.05). Researchers noted that broadleaf cattail emergence in the field was substantially less than in the greenhouse. Frequency of broadleaf cattail seedlings in the field ranged from 0 to 47% over a 2-year period in 2 vegetation types [126]. See Seed banking for more on seedling emergence results from Leck and Simpson's [126] study.
Nutrients and extracts: Some studies report differences in percent germination and germination rates when broadleaf cattail seeds are exposed to leaf litter extracts and nutrients. Germination rate increased but total percent germination was not different when seeds from the northern Florida Everglades were kept moist with Everglades water rather than distilled water. Everglades water with low, medium, and high levels of total phosphate was tested [198].
Germination was nearly a complete failure when seeds collected from broadleaf cattail marshes near Syracuse, New York, were kept moist with broadleaf cattail leaf extracts. In distilled water, broadleaf cattail germination was 90.8% after only 2 days. The researcher described the inhibition as "autotoxic feedback", a process by which seedling viability decreases with accumulations of toxic parent residues [148]. Germination of broadleaf cattail seeds from Washington County, Arkansas, was inhibited by 3% broadleaf cattail leaf extract concentrations, but inhibition was due to the development of water molds. There were no significant differences in germination of seeds planted in pots with (82%) or without (86%) adult broadleaf cattail (P>0.05). Light levels were high (81% full sun) and litter accumulations were low in the pots, which is not representative of a natural broadleaf cattail stand [74]. In natural broadleaf cattail marshes in Crawford County, Pennsylvania, light was less than 3% at the soil surface [23].
Broadleaf cattail hybrids: Increased sediments and flooding reduced broadleaf cattail à narrow-leaved cattail germination percentages. Germination of broadleaf cattail à narrow-leaved cattail seed collected from Larson Marsh in Story County, Iowa, decreased by 60% to 90% when 2 to 4 mm of sediment were added to the soil surface [218]. In the greenhouse, broadleaf cattail à narrow-leaved cattail and broadleaf cattail germination was 15% and 16%, respectively, in 16 inches (41 cm) of water. Germination was best in 1 inch (2.5 cm) of water, and germination percentages decreased with increasing water depths [225].
Seedling establishment/growth: Broadleaf cattail seedlings are extremely small when compared to seedlings of associated vegetation. Drawings of typical broadleaf cattail seedlings are provided by Leck and Simpson [125]. After germination, broadleaf cattail produces 2 to 4 small leaves and 2 to 6 floating leaves before producing erect leaves. Once shoots reach 14 to 18 inches (35-45 cm) tall, rhizome growth begins (Holm and others as cited in [155]). Flooding and sediments can affect seedling survivorship and growth.
Flooding: Some indicate that broadleaf cattail seedling establishment is most likely on nonflooded substrates [16,189]. However, Yeo [238] observed that nearly all broadleaf cattail seedlings in the field were submerged in early growth. At the Aquatic Environmental Research Facility in Lewisville, Texas, broadleaf cattail seedling biomass was measured 10 weeks after germination at 0- to 47-inch (120 cm) depths. Seedling biomass was greatest at 7.9 inches (20 cm) and least at 47 inches (120 cm). Unflooded conditions produced seedling biomass greater than flooding with 24 or more inches (>60 cm) [188].
Hybrid seedlings/growth: Broadleaf cattail à narrow-leaved cattail seedling survivorship was much lower in 1 cm of sediment than when no sediment was present, and younger seedlings were more sensitive to sedimentation than older (26-37 days) seedlings. Survival decreased when over half of the shoot was covered. Survivorship increased when older, larger seedlings received small amounts of sediment. Sediment loads of up to 1.6 inches (4 cm) did not affect adult plant densities [218].
Growth: Typical broadleaf cattail growth and development were summarized after 3 years of studies on the west side of Lawrence Lake in Michigan. There are 3 shoot emergence pulses/year; one occurs in the early spring, with spring shoots dying by late fall. In midsummer another pulse of growth occurs, and 70% to 80% of shoots die in the fall. The last growth pulse produces 80% to 90% of the shoots that will resume growth in spring [45]. The rhizome is the most long-lived broadleaf cattail structure; it survives up to 2 years (Westlake, cited in [45]). Broadleaf cattail growth and production can be affected by soil moisture regimes and associated species presence.
Broadleaf cattail biomass production and height growth were greatest for continuously flooded seedlings in a greenhouse experiment. Researchers collected broadleaf cattail seed in March from freshwater wetlands along the Mississippi River in Tennessee. Seedling biomass production and height growth were significantly lower in periodic drought conditions than in continuously flooded conditions (P<0.001) [131].
At the W. K. Kellogg Biological Station in Michigan, broadleaf cattail shoot density was 32% lower when growing with narrow-leaved cattail than when growing in a monoculture [81].
Vegetative regeneration: Rhizome growth is important to broadleaf cattail regeneration. Rhizome dispersal may occur when portions of a clone are separated by wind, water, ice, or animals [6]. Dispersal is also likely through tillage and substrate movement [47].
Broadleaf cattail is highly productive through clonal growth. Broadleaf cattail clones can occupy 58 m² two years after germination [77]. Holm and others [102] reported in a review that a single broadleaf cattail colony was 54 m² after 2 growing seasons and produced a total rhizome length of 1,600 feet (480 m). A plant grown from seed produced rhizomes that reached a diameter of 10 feet (3 m) in a single growing season [238]. Nearly monotypic broadleaf cattail stands are multiclonal [109]. Broadleaf cattail ramets typically die within a year. If the ramet flowered, it was very unlikely to live beyond 1 year. In undisturbed broadleaf cattail stands, ramets were not over 3 years old [78].
In many cases, vegetative regeneration predominates over sexual reproduction. Some indicate that seedlings rarely occur in established broadleaf cattail stands [78] and that rhizome production and growth are the primary methods for increasing stand size [44]. Researchers collected seed for 3 years from an established high-elevation broadleaf cattail stand near Grand Lake, Colorado. No seed germinated, but vegetative growth was described as vigorous [149]. A total of 1,765 broadleaf cattail shoots were monitored in the western marsh of Lawrence Lake in south-central Michigan over a 2-year period. There were no seedlings, and only 2 shoots flowered. Researchers summarized that "through vigorous vegetative growth", a dense, monotypic broadleaf cattail stand produced a "tightly packed advancing front of ramets" that successfully excluded other plants [44]. After a series of field experiments, researchers concluded that broadleaf cattail "is exploitive in its ability to clone rapidly and colonize available space, is able to capture light effectively because of its high allocation to leaves and high leaf surface area, and as a result has a low allocation to sexual reproduction" [79].