Definition of Non-native Invasive Species: "Plant or animal... that is non-native to the ecosystem... likely to cause economic and environmental harm"
Why are non-native invasive plants (NNIP) a problem?
- They are introduced where they did not evolve, thus they have no natural enemies to limit their numbers
- Their rapid growth rate and high reproductive rates allow them to quickly invade new habitats
- They outcompete native plants, especially when an ecosystem is stressed
- NNIP span landscapes, ownerships, and jurisdictions
- Some are toxic, like spotted knapweed, poison hemlock, and wild parsnip to name a few.
Threats include: replacing native ecosystems, reduce biodiversity, change ecological processes, recreational opportunities degraded, wildlife and livestock grazing habitat compromised.
UPIC's Top Twenty
#1 Garlic mustard (Alliaria petiolata)
Garlic mustard is a cool season biennial herb with stalked, triangular to heart-shaped, coarsely toothed leaves that give off an odor of garlic when crushed. First-year plants appear as a rosette of green leaves close to the ground. Rosettes remain green through the winter and develop into mature flowering plants the following spring. Flowering plants of garlic mustard reach from 2 to 3-1/2 feet in height and produce buttonlike clusters of small white flowers, each with four petals in the shape of a cross. Once introduced to an area, garlic mustard outcompetes native plants by aggressively monopolizing light, moisture, nutrients, soil and space. Image: Chris Evans, River to River CWMA, Bugwood.org
#2 Purple loosestrife (Lythrum salicaria)
Purple loosestrife is a perennial, herbaceous plant with one to 50 square stems, so the plant can have a bushy appearance. Its leaves are opposite or whorled, lance-like and rounded at the base. The plant flowers from June to September and its flowers are magenta with five to seven petals each. Image: John D. Byrd, Mississippi State University, Bugwood.org
#3 Glossy buckthorn (Frangula alnus)
This shrub has gray to brown bark with white lenticels (elongated spots) perpendicular to the stem; dark green leaves that are shiny, alternate (sometime opposite) and simple with prominent veins and no teeth. In the spring, inconspicuous pale yellow flowers occur in clusters in the leaf axis. Small fleshy fruit ripens to a dark purple color. Habitats: moist woodlands, wetlands, acidic bogs, calcareous fens and sedge meadows; alvars; also in upland habitats. Threats: quickly spreads into natural areas and is tolerant of a wide range of conditions including shade. The seeds are viable 2-3 years in soil and it has an extensive root system and a long growing season. Notes: Looks similar to many native and other non-native shrubs. Native to Eurasia.
#4 Spotted knapweed (Centarurea biebersteinii)
Spotted knapweed is a short-lived, perennial forb native to Eurasia. It releases a toxin into the soil that hinders or prevents the growth of surrounding plants. It reproduces by seed and can produce thousands of seeds per plant, each of which is viable for more than 3 years. It grows up to 2-4 feet and has a stout taproot. Always use gloves when working with this plant. This plant is of major concern in many habitats, especially dunes, lakeshores, agricultural fields, prairies, and alvars throughout the Upper Peninsula.
#5 White sweet clover (Melilotus alba)
White Sweet Clover is an aggressive biennial native to Eurasia that degrades habitats by shading out other species. The leaves are clover like and divided into three finely toothed leaflets; the plant has small white flowers on a long stalk. The deep taproots are semiwoody and difficult to remove. The plant reproduces soley by seeds and produces up to 350,000 seeeds per plant that can remain viable in the soil for 30 years. This species is of particular concern along the shoreline habitats of Lake Michigan where it can form dense stands and degrade habitat for native flora and fauna. Image: Jan Samanek, State Phytosanitary Administration, Bugwood.org
#6 Japanese knotweed (Polygonum cuspidatum)
Habitats: riparian areas; disturbed stream sides, lakeshores Threats: spreads vegetatively and forms dense thickets that outcompete native plants. It is tolerant of full shade, high temps, and high salt content and drought. Flowers: white, plume-like flowers boom in August and September Notes: Once it becomes established, Japanese knotweed stands are extremely difficult to eradicate. Native to: Asia Image: Jan Samanek, State Phytosanitary Administration, Bugwood.org
#7 Eurasian watermilfoil (Myriophyllum spicatum)
Habitats: Lakes; slow moving rivers and streams Threats: Forms dense mats that outcompete native plants and interfere with ecosystems. Notes: Reproduces by fragments, runners, and seeds. The native Milfoil has less than eleven segments on one side of the leaf, while the invasive Eurasian watermilfoil has more than eleven. If you suspect you might have the invasive Milfoil, contact your local conservation office. Native to Eurasia and northern Africa Image: Alison Fox, University of Florida, Bugwood.org
#8 Reed canary grass (Phalaris arundinacea)
Habitats: wetlands, now invading shaded areas Threats: a major threat to wetlands. Forms monotypic stands to the exclusion of other plants. Flowers: sod-forming perennial; blooms May to mid-June Notes: The introduced European variety is more aggressive, and there is currently no way to visually differentiate between the native and Eurasian strain. Native status: although native to North America, some strains are very invasive and are believed to be introduced varieties Image: Richard Old, XID Services, Inc., Bugwood.org
#9 Phragmites (Phragmites australis - Common reed)
Habitats: wetlands, riverbanks, lake shores Threats: creates impenetrable stands to the exclusion of native plants. Spreads by extensive rhizomes. Flowers: July-September. Notes: Extremely difficult to eradicate. Very tall, from 3 to 20 feet high. Note: Although native to North America, some strains are very invasive and are believed to be introduced varieties. Visit www.invasiveplants.net for identification. Image: James H. Miller, USDA Forest Service, Bugwood.org
#10 Japanese barberry (Berberis thunbergii)
Habitats: open and wooded habitats, wetlands, and disturbed habitats. Prefers to grow in full sun to part shade, but will flower and fruit even in heavy shade. Threats: Barberry is shade tolerant, drought resistant, and adaptable to a variety of habitats. It leafs out early and can shade out native plants and may also change the soil chemistry in areas it inhabits. Japanese barberry spreads by the large numbers of seeds and by vegetative expansion. Flowers in May Notes: has bright red berries and small, spoon-shaped leaves. Unfortunately it is still sold as an ornamental. Native to: Eurasia Image: Britt Slattery, U.S. Fish and Wildlife Service, Bugwood.org
#11 Non-native bush honeysuckles
Habitats: riparian areas; disturbed stream sides, lakeshores, wooded areas Threats: spreads vegetatively and forms thickets that outcompete native plants. Research has shown that robins and wood thrushes that nested in exotic buckthorns and honeysuckles suffered more predation than those nesting in native shrubs. Flowers: fragrant, showy flowers in May to June. Notes: there are native bush honeysuckles, but whereas the non-native invasives have hollow brown stems the natives have white and solid stems, are are low growing, occupy different habitats. Native to Eurasia Image: Chuck Bargeron, The University of Georgia
#12 Leafy spurge (Euphorbia esula)
Habitats: roadsides, fields, prairies and savannas Threats: in natural areas it destroys wildlife habitat by displacing native grasses and forbs in only a few years. Flowers: blooms from June into fall Notes: toxic to humans and animals Native to southeastern Europe’s scrub oak forests Image: Norman E. Rees, USDA ARS
#13 Autumn olive (Elaeagnus umbellata)
Habitats: disturbed areas, roadsides, open woods, forest edges, prairies, pastures, sand dunes, poor soils Threats: can disrupt native plant communities that require infertile soil Flowers: light yellow, tubular in May or June Notes: Native shrubs that look somewhat similar include Silver buffaloberry and Russet buffaloberry. Native to China, Japan, and Korea Image: James R. Allison, Georgia Department of Natural Resources, Bugwood.org
#14 Non-native Marsh thistle (Cirsium palustre)
Habitats: marshes, riparian areas; disturbed stream sides, lakeshores Threats: the large rosettes can outcompete native plants. Grows up to 6 feet tall and has thick, reddish-colored, thorny steams. Flowers: June to July Notes: The native Marsh Thistle (Cirsium muticum) has non-spiny stems and flower heads. Other common invasive thistles include Canada thistle (Cirsium arvense) which has spiny leaves but non-spiny stems and flower heads. Bull thistle (Cirsium vulgare) and Plumeless thistle (Carduus acanthoides) which have sharply spiny leaves, stems and flower heads. Native to Europe Photo by Steve C. Garske, GLIFWC, from University of Wisconsin- Stevens Point
#15 Giant hogweed (Heracleum mantegazzianum)
Stems are hollow and ridged with purple blotches and coarse white hairs; Leaves are up to 5 feet across, lobed and deeply incised; several small white flowers are clustered in a flat-topped umbel up to 2.5 feet across. Resembles cow parsnip, angelica, and poison hemlock, but much larger. Very hazardous to humans, causes severe skin irritation with blisters after contact Image: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org
#16 Wild parsnip (Pastinaca sativa)
Habitats: disturbed areas; once established, can invade open dry, moist and wet-moist habitats; prairies and oak openings. Can grow up to 4 ft. (1.2 m) in height; Leaves are alternate, compound and branched with jagged teeth. Flowers: Hundreds of small yellow flowers in umbels; blooming June to late summer Threats: Invades and modifies open, disturbed habitats. Notes: the leaves, stems, flowers, and fruits can cause severe skin reactions. Native to Europe and Asia Image: Joseph M. DiTomaso, University of California - Davis, Bugwood.org
#17 St. Johnswort (Hypericum perforatum)
St. Johnswort is a plant introduced from Europe commonly uses as an herbal medicine. There are native Hypericum species in Michigan so identification is important. One key is to look for small dots on the edges of the underside portions of the leaves. This plant can invade open areas, and is a major concern in the rare alvar habitats along Lake Michigan and Lake Huron. Image: John Cardina, The Ohio State University, Bugwood.org
#18 Baby's breath (Gypsophila paniculata)
Habitats: dunes, roadsides; sunny alkaline sands Threats: invasive on dune habitats; produces 14,000 seeds per plant; still sold commercially Flowers: July-August Notes: Very difficult to remove Native to eastern Europe and Siberia. Image: Steve Dewey, Utah State University, Bugwood.org
#19 Common forget me not (Myosotis scorpioides)
Habitats: shallow water, stream borders, wet soil, and forests Threats: although beautiful, these plants can escape from gardens and become very dense, eliminating important native vegetation. Flowers May to October Identification is extremely important!! The non-native forget-me-nots are similar to native “Bay forget-me-not” (Myosotis laxa). Native to Europe Image by Tom Heutte, USDA Forest Service, Bugwood.org
#20 Norway maple
Habitat: woodlands Threats: The shallow, fibrous root system and dense shade of Norway maple make it difficult for native plants to grow. It has escaped the urban environment and is a threat to native maples. Notes: distinguishable from native sugar maple by the fruit (The angle of seed wings is approximately 180 degrees for Norway maple, 120 degrees for sugar), sap (broken leaf petioles of Norway maple ooze white sap, while the sap of sugar maple is clear) and bark (Norway maple bark is regularly grooved, sugar maple bark has irregular plates). the leaves are often covered with a black fungus called “tar spots” in the fall. Native to Europe and western Asia. Introduced to N. America in 1756. Continues to be sold as ornamental. Image: Bill Cook, Michigan State University, Bugwood.org
