New and Spreading Invasive Plant Species in DuPage County Forest Preserves Office of Natural Resources April 2013
Terrestrial Species Known from DuPage County
Black Swallow-wort (Cynanchum nigrum) Perennial twining herbaceous vine Oval, opposite leaves with pointed tips Dark purple five-petaled star shaped flowers Slender milkweed-like pods Forms large patches due to rhizomes Invades forests, woodland edges and grasslands Currently known from Des Plaines Riverway, St. James Farm and Waterfall Glen, as well as the Morton Arboretum
Japanese Hops (Humulus japonicus) Climbing annual herbaceous vine Downward pointing, rough prickly hairs on stems and leaves Leaves are opposite and palmately divided into 5 or more lobes Petioles are as long or longer than the leaves Invades floodplains
Native vs. Non-native Hops Native Hops Non-native Hops Common hops (Humulus lupulus) has Japanese hops has 5 lobes per leaf (rarely 3 lobes per leaf (rarely 5) that are 3) that are pointed and the flowers are rounded. Flowers are yellow to white. greenish.
Giant Hogweed (Heracleum mantegazzianum) Federal Noxious Weed Can grow up to 15 feet in height Causes phyto-photodermatitis Escapes to moist soil along roadsides and stream banks Prolific seed producer can spread rapidly First found at Waterfall Glen in 2001, also at Morton Arboretum
Narrow-leaved Bittercress (Cardamine impatiens) Flowers are in rounded clusters There are both basal and alternate stem leaves Where the leaf joins the stem are a pair of narrow pointed lobes (auricles) Basal leaves are compound in groups of 3 to 11 with rounded lobes Fruits are straight slender pods erect to spreading - ~ 1 in long First found at Timber Ridge (Mains Property) in 2009 Controlled by hand pulling
Waxy Mannagrass (Glyceria declinata) Perennial grass though often acts like an annual Usually spreads through seeds Has invaded vernal pools in California First found at Blackwell in 2009, but has not been observed at the site since that time
Flowering Rush (Butomus umbellatus) Large aquatic perennial Thin sword-shaped leaves that are triangular in cross-section Three large pink petals and three sepals Bulbils may be present at the base of the flower stalks and aid in dispersal Rhizomes fleshy and grow trailing along the ground First found in Springbrook Prairie
Porcelain Berry (Ampelopsis brevipedunculata) Deciduous, woody climbing vine Plant has branched tendrils native grapes are un-branched Climbs to heights of 20 ft or more Leaves vary from slightly lobed to highly dissected Bark has lenticels and does not peel Stem pith is white on native grape is brown Fruits ripen at different times
Japanese Parsley (Oenanthe javanica) Perennial growing to approximately 3 feet White umbel-like flowers Stems are cylindrical and upright from a creeping base Prefers wet soils and can grow in water Flowers from June through August Seeds ripen from August to October Horizontal, rooting stems spreads rapidly Bearing pinnate, alternate green leaves with ovate, toothed leaflets Found at West DuPage Woods in 2000 not accurately identified until recently
Lesser Celandine (Ranunculus ficaria) Perennial herbaceous species that grows in early spring Glossy, dark green, rounded leaves arranged in a low-growing rosette with both fibrous and tuberously thickened roots Leaves appear in late winter and die back by early June Bright yellow buttercup-like flowers bloom in March and April, held above the leaves Characteristic of moist alluvial soils in forested floodplains
Differences between invasive Ranunculus ficaria and native Caltha palustris Lesser celandine may be confused with marsh marigold (Caltha palustris), a native plant found in wetland habitats in the county. Marsh marigold is a robust plant with glossy, rounded or kidneyshaped leaves and flowers on stalks that are 8 in. or more tall and consist of five to nine deep yellow "petals" (actually sepals). Marsh marigold does not produce tubers or bulblets, nor does it form a continuous carpet of growth. Extreme care should be taken to correctly identify lesser celandine before undertaking any control measures to avoid impacts to the native plant. It also resembles celandine (Chelidonium majus) and celandine poppy (Stylophorum diphyllum), both of which belong to the poppy family and can be distinguished from the invasive buttercup by having flowers with four petals. Lesser celandine Marsh marigold
Globe Thistle (Echinops sphaerocephalus) Glandular, wooly, erect branching perennial that can reach 6 feet Typical thistle leaves are sticky, hairy above and white wooly below At the end of each stem is an almost perfectly spherical inflorescence that has white or blue-gray flowers Flowers from July to September Rarely seen in DuPage Co.
Ornamental Pear (Pyrus calleryana) Tree that grows 30-50 feet tall Leaves 2-3 inches wide, heartshaped to rounded margins wavy with fine teeth Flowers in March-April with white flower clusters Fruits green to brown with pale dots spreads by seed
Silver Grass (Miscanthus sacchariflorus) Perennial warm season grass from 6 to 8 feet tall Leaf blade is arching with a distinct whitish midrib Silky plume-like inflorescence produced in late summer and early fall Plants produce very little seed; spread primarily through aggressive rhizomes Differs from M. sinensis by having no awns on the spikelets
Slender-leaved Maiden Grass (Miscanthus sinensis) Basal leaves arise from a central clump Leaves are long and arching being pubescent on both sides and slightly serrated along the edges Flower stalks are about 6 feet tall and initially reddish, turn tan in fall Flowers emerge from September to November Spreads primarily by rhizomes Popular ornamental grass First found in DuPage County in 2010 variety gracillimus represented
Differences between M. sinensis and M. sacchariflorus
Terrestrial Species Not Yet Known from DuPage County
Pale Swallowort (Cynanchum rossicum) Long-lived perennial, twining herbaceous vine The small five-petaled, star shaped flowers are creamy Pink to reddish brown, about ¼ in. across, and are borne in clusters Fruits slender tapered pods, 2-3 in. long by about ¼ in. wide, that turn from green to light brown as they mature. The leaves are oval shaped with pointed tips, 3-4 in. long by 2-3 in. wide, and occur in pairs along the stem Not yet seen in DuPage County or northeastern Illinois In contrast to its invasive relative, the black swallow-wort, pale swallow-wort does not have rhizomes. Plants tend to grow in clumps of several to many stems, forming extensive patches.
Japanese Stiltgrass (Microstegium vimineum) Annual grass weak rooted and sprawling Leaves pointed at both ends Silvery, off-center midrib often present Often has multiple stems Flowers late summer through early fall Found recently in Will and McHenry counties
Mile-a Minute Weed (Polygonum perfoliatum) Herbaceous, annual, trailing vine Stems armed with re-curved barbs Light green leaves shaped like equilateral triangles - arranged alternately on stem Circular, cup-shaped leafy structures, called ocreae, surround the stem at nodes Flowers are small, white and generally inconspicuous Fruits are deep blue and arranged in terminal clusters
Kudzu (Pueraria montana var. lobata) Climbing semi-woody, perennial vine in the pea family Leaves are alternate and compound with 3 broad leaflets they may be entire or 2-3 lobed Flowers are purple, about ½ inch long, highly fragrant and in long hanging clusters Flowering occurs in late summer and is soon followed by production of brown, hairy, flattened, seed pods, each containing 3 to 10 hard seeds
Chinese Yam (Dioscorea oppositifolia) Perennial, high climbing herbaceous vine Stem grows from large root-like tubers and twines clockwise Blooms in summer spreads vegetatively via bulbils (small potato-like tubers in leaf axils) Flowers are small and white, arranged in spikes, and have a cinnamon odor Leaves deeply lobed and concave at the base Leaves are opposite with the upper nodes alternate, and are reddish where the leaf stem joins the leaf
Native vs. Non-native Yams Non-Native Native Dioscorea oppositifolia purple leaf base Shield shaped leaf Dioscorea villosa green leaf base heart-shaped leaf
Silky Bush-Clover (Lespedeza cuneata) Perennial forming dense patches Leaves alternate, divided into three leaflets which are hairy and wedge-shaped narrowest at base broadening to tip Flowers solitary or in clusters of 2-3 from base of leaves white to cream with purple in center Stems and branches grayish green with stiff hairs Spreads by seed and vegetatively from root crown Lespedeza davurica (Dahurian Bush Clover) was found at Pratt s Wayne in 2001.
Native vs. Non-native Bush Clovers Non-Native Native Silky bush clover has flowers along stem Round headed bush clover has flower cluster at top of stem
Aquatic Species
Brazilian Waterweed (Egeria densa) Robust, submerged, perennial aquatic plant Very leafy with bright green leaves in whorls of 4-8 Leaves are 1-3 cm long with fine serrations Produce white staminate flowers primary reproduction is by plant fragments Aquarium dumping is the major pathway to spread Found at West DuPage Woods in 1996
Hydrilla (Hydrilla verticillata) Aquatic, herbaceous, submerged perennial Can grow in water up to 20 feet deep Stems submerged, branched across surface Leaves green in whorls of 5 leaf edges saw-toothed Reproduces vegetatively, also by turions and tubers
Differences between Egeria densa, Elodea canadensis and Hydrilla verticillata Brazilian waterweed (Egeria densa) is a very bushy plant with dense whorls of bright green leaves (except when growing with insufficient light, in which case the leaves are widely spaced). Brazilian waterweed usually has four leaves per whorl (arranged around the stem) and each leaf is at least 2 cm long. Common Waterweed (Elodea canadensis) is smaller than Brazilian waterweed and generally has three leaves per whorl. Each leaf is usually less than 1 cm long. Hydrilla (Hydrilla verticillata), probably the most dreaded aquatic invader of the United States, has five leaves per whorl and tiny spines along the leaf margins. The midrib of each leaf is often reddish. Hydrilla produces tubers (small potato-like structures). Neither Brazilian elodea or American waterweed has tubers.
Differences between Egeria densa, Elodea canadensis and Hydrilla verticillata
Brittle Naiad (Najas minor) Highly invasive, submersed annual aquatic plant introduced into the United States from Europe The stems also fragment readily, hence the common name "brittle" naiad Leaves are opposite, strap-shaped, about 1 in length, and have prominent marginal teeth. Found in lakes, ponds and wetland restorations in DuPage County First found in the Chicago Region in DuPage County in 1997 now known from 15 preserves
Najas minor vs. Najas flexilis
Water Lettuce (Pistia stratiotes)
Water Hyacinth (Eichhornia crassipes)