Common/Botanical
Name

Description

Origin

Reproductive
Capacity

Invasive Potential

Amur Maple
Acer ginnala

A small (20’) tree with double-tooth- edged leaves have shallow lobes. In spring, small fragrant, pale yellow flowers appear as leaves unfold. Two- winged, inch-long seeds mature in late summer.

Native of Eastern Asia. Introduced into U.S. and Canada in 1860s.

One tree can produce more than 5,000 two-winged seeds that are widely spread by wind.

In open woods, it displaces native shrubs and understory trees. In prairies and open fields, it can shade out native species.

Boxelder

Acer negundo

Large (30-50’) tree adaptable to wet or dry soils. Leaves have 3-5 leaflets opposite each other on the stem. Female trees produce many two-winged seeds. New stems are a waxy gray-blue, turning green when rubbed.

Native to U.S., particularly along riverbanks and floodplains.

It can spread by suckers, root shoots, and a prolific number of wind-borne seeds. It readily establishes in disturbed areas, including fencelines, near buildings, abandoned roads, railroad beds, dumps, and farm fields.

It quickly establishes thickets that shade out smaller, more desirable plants.

Norway Maple

Acer platanoides

A 40-50’ tree with a leaf shape like its cousin the sugar maple. Unlike the sugar maple, Norway maple leaves have a milky sap when broken, and their fall color is limited to yellow (except for the maroon-leaved varieties).

Native to Europe, this tree was introduced in Philadelphia in 1792 as an ornamental street tree. Today, it is the most commonly planted street tree in the U.S.

It spreads by prolific production of wind-borne, two-winged seeds.

It is easily established in open woodlands and fields. Shade tolerant and an efficient user of water and nutrients, it can out- compete native sugar maple and beech. Its dense canopy limits wildflowers and other understory herbaceous growth.

Porcelain Vine Ampelopsis brevipedunculata

Perennial vine with deeply lobed leaves, which are sometimes variegated. In fall, its abundant clusters of large, shiny berries turn blue and purple mottled with white and gray.

Introduced from northeast Asia in 1870.

Its abundant seeds have a very high germination rate. It also reproduces vigorously from its roots and from stems in contact with the soil.

This vigorous vine forms a tangle that covers the ground as well as woodland trees and shrubs, blocking out sunlight and competing for nutrients and water. It colonizes at woodland edges and gaps, as well as in any sunny, disturbed area, such as highway shoulders, railroad beds, riverbanks, shorelines, and fields.

Japanese Barberry Berberis thunbergii

This shrub grows 3- 6’ tall. It is most easily identified by its small, rounded leaves, spiny stems, and red berries that develop in summer.

Native to Asia, it was introduced around 1875.

Birds and rodents eat the fruits and distribute the seeds widely. Its branches form roots when in contact with the soil. This, and the shrub’s vigorous root system, helps it form thickets.

It invades woodlands, preventing growth of understory shrubs and other plants.

Oriental Bittersweet Celastrus orbiculatus

A deciduous, twining vine that can grow to five inches in diameter and up to 60 feet long. It is differentiated from American bittersweet by its yellow and red fruits, which appear all along the stems. American bittersweet bears fruit only at the stem tips.

Native to Asia, this plant was introduced in the mid 1800s. Grown for its berries which are used in flower arrangements.

Birds are the primary means of seed dispersal. This plant also spreads vigorously through suckers.

This vine flourishes in open woods, thickets, and roadsides where it aggressively competes for water, nutrients, and sunlight. Through twining, it restricts the host plant’s sap flow. It can also make the host top-heavy and subject to wind damage.

Autumn-olive Elaeagnus umbellata

This shrub can grow up to 20’ high and wide. Its gray-green leaves are shorter and less silvery than Russian-olive. It has fragrant yellow flowers that emerge after the leaves in spring and mature into bunches of red fruits in fall.

Native to Asia, this plant was introduced in 1917. Valued for its use as a forage plant in wildlife areas, this vigorous shrub now dominates many untended areas from fencerows to meadows to open woods, sand dunes, and railroad rights of way.

Just one shrub can produce up to 200,000 seeds a season. These are widely distributed by birds.

This shrub grows rapidly into a dense thicket, choking out native plants.

Burning Bush Euonymus alatus

Burning bush is often 12’ tall and can reach 15-20’ high and wide. It’s identified easily by four corky “wings” on the stems and its brilliant red fall color.

Native to northeast Asia, this plant was introduced in the 1860s for its ornamental value.

This shrub is spread by birds that eat the seeds. It can tolerate many conditions, from full sun to nearly full shade and from very dry to moist soils.

This shrub has begun invading open woodlands, mature second-growth forest ravines, and hill prairies, out-competing many native plants. Rarely a problem in urban landscapes.

European Privet Ligustrum vulgare

This deciduous shrub grows 12-15’ high and wide. This densely-branched, irregularly shaped plant is most easily identified by its clusters of fragrant small white flowers from May through June. Its lustrous black fruit ripens in fall and remains on the shrub often until the following spring.

Native to Europe, this plant was introduced into the U.S. around 1850 and has been widely used for hedges.

Birds spread the seeds of this prolific producer. The plant also suckers aggressively.

This extremely aggressive shrub is crowding out native plants along natural areas including river bottoms, and open woods, as well as in fencerows, vacant lots, old fields, and roadsides.

Japanese Honeysuckle Lonicera japonica

Semi-evergreen woody vine that has fragrant, tubular flowers that start white (may be tinged with pink or purple), and turn yellow as they mature. The twining vine grows 15-30’ long and has black berries that ripen in fall.

A native of eastern Asia, this plant was introduced into New York in 1806.

The vine is spread by birds that eat the fruits. It grows aggressively and has become such a problem that its sale and distribution are prohibited in Illinois.

This vine spreads rapidly, crawling along fields, fencerows, and roadsides smothering everything in its path. In woodlands, it grows over the tops of trees and shrubs, engulfing them.

Amur Honeysuckle Lonicera maackii

This upright, spreading, leggy deciduous shrub grows 12-15’ tall and wide. It can best be differentiated from native species because it leafs out several weeks earlier in spring and holds its leaves longer in fall. It has white, 1”- long flowers that turn yellow, and red berries that ripen in October.

Native to Asia, this plant was introduced into North America in 1896. Illinois is one of the states where it has been most invasive.

In addition to being a vigorous, aggressive grower, Amur honeysuckle seeds are widely spread by birds.

Amur honeysuckle colonizes a wide variety of habitats, turning prairies into scrub and reducing the plant diversity and density of woody seedlings in the ground layers of woodlands. Because they leaf out early, they shade out spring-blooming woodland wildflowers.

White Mulberry Morus alba

Deciduous tree growing 30-50’ tall and wide. Its extremely dense, rounded form is composed of tight- knit slender branches, often developing witches’ broom. Its leaves may be either undivided or lobed. In summer, it develops fruits resembling blackberries.

Native to China, this plant was imported by early settlers in Jamestown, Virginia for the silkworm industry.

This tree is spread by birds who love its berries. The white mulberry flourishes in a variety of cultural conditions and adapts to drought, salt, and urban soils.

This tree is rarely a problem in undisturbed woodlands. It naturalizes in disturbed woodlands, and along railroads, back alleys, floodplains, and open lots.

Amur Corktree Phellodendron amurense

This medium-sized shade tree grows 30- 45’ tall with an equal or greater spread. Its compound leaves are 10-15” long and include 5-11 leaflets. The bark of older trees is gray-brown and cork-like in texture. Inconspicuous yellow-green flowers appear in late spring followed by ½” black fruits which have an unpleasant odor when bruised.

Native to Asia, this tree was introduced to the U.S. in 1856.

Seeds spread by birds. Establishes itself in woodlands and along streams.

Female plants produce seed and should be avoided. Seedless male selections are becoming available in the nursery trade.

Common Buckthorn Rhamnus cathartica

A tall shrub/small tree that can grow to 20’ tall. The leaves, which appear earlier than most natives in spring and persist beyond most natives in fall, are a dull green and elliptical. Twigs often have thorn-like spurs. Female plants bear round, dark blue fruits in May and June that ripens to black in August and may persist for much of the winter.

Native to Europe and Asia, these plants were introduced during the 1800s as ornamental hedgerows.

Birds widely disperse its seeds. Once established, this plant quickly develops dense thickets that out- compete other plants. It grows rapidly in a variety of conditions, from full sun to shaded understory, and resprouts vigorously when cut back.

Bird-dispersed seed has a high germination rate in a variety of habitats including gardens, fencerows, pastures, prairies, roadsides, and abandoned farm fields. In woodlands, it can completely replace existing understory plants, including spring- flowering wildflowers.

Glossy Buckthorn Rhamnus frangula

This multi-stemmed shrub/small tree can grow 10-15’ tall. The elliptical leaves, which appear earlier than most natives in spring and persist beyond most natives in fall, are glossy green on top and somewhat hairy underneath. Female plants bear round, red fruits in May and June that ripen to black in August and may persist for much of the winter.

Native to Europe and Asia, these plants were introduced during the 1800s as ornamental hedgerows.

Birds disperse its seeds. Once established, this plant quickly develops dense thickets that out- compete other species. Although it favors wetlands, it can also become established on dry sites. It grows rapidly in a variety of conditions, from full sun to shaded understory, and resprouts vigorously when cut back.

Bird-dispersed seed has a high germination rate in a variety of habitats including bogs, marshes, river banks, pond margins, gardens, fencerows, pastures, prairies, roadsides, abandoned farm fields. It is much less shade tolerant than common buckthorn.

Black Locust Robinia pseudoacacia

This fast-growing tree reaches 30-80’ tall. Its dark blue- green leaves are 6- 14” long with 7 to 21 leaflets. In May to early June, the tree has fragrant, white, pea-like flowers in large, drooping racemes. Later, shiny, flat, 2- 4” long seedpods develop.

This tree is native to the eastern U.S. Its rapid growth, extensive, soil-holding root system, high fuel value, and flowers that provide an attractive food source for bees are among the reasons it was widely planted.

Black locust creates expansive, dense stands through seed germination and suckering.

Outside its original range this tree can out-compete native species in most dry, disturbed environments including upland forests, savannas, prairies, pastures, roadsides, and old fields. Its seeds, leaves and bark are toxic to humans and animals.

Multiflora Rose Rosa multiflora

A dense, spreading shrub that can grow 10-15’ tall with arching canes and stiff, curved thorns. Unlike native roses, which usually have pink blossoms, the multiflora has clusters of white flowers, which mature into ¼” red seeds or “hips” that persist through the winter.

A native of Japan, this plant was introduced in 1886 as rootstock for cultivated roses. Later, the U.S. Soil Conservation Service encouraged its planting to curb soil erosion.

A single plant can produce up to 500,000 seeds a year. These seeds can remain viable in the soil for up to 20 years. In addition to dispersal by birds, multiflora rose can create dense thickets by suckering.

Multiflora rose readily invades pastures, prairies, savannas, open woodlands, forest edges, and roadsides.

Poison Ivy Toxicodendron radicans

This plant grows as a vine that climbs trees, a ground cover, or an upright shrub. Although its leaves are somewhat variable, they normally appear as three leaflets. This plant produces small, off-white flowers and later yellow-white berries that are usually hidden by the foliage. In fall, leaves turn a brilliant red.

This native species is opportunistic and can become very aggressive in any areas disturbed by human activities including trails, parks, yards, recreation areas, dunes, shorelines, and woodlands.

Spreads by seed and vigorous growth. Often found in abandoned fencerows and clinging to large mature trees.

Although there is little evidence that poison ivy is threatening native flora, it is very troublesome to most people. Oils from the leaves and stems, as well as smoke from burning poison ivy, can cause potentially serious dermatitis.

Siberian Elm Ulmus pumila

This fast-growing tree is 50-70’ tall with a round, open crown. It has small, elliptical leaves that are usually less than 2 inches long. Greenish flowers appear in small, drooping clusters before the leaves unfurl in spring. Later, the one- seeded, winged fruits hang in clusters.

A native of Asia, this tree was introduced to the U.S. in the 1860s. It was valued for its rapid growth and ability to adapt to a variety of conditions, including poor soil and drought.

Windswept seeds germinate prolifically, often forming thickets of hundreds of seedlings.

This tree can dominate a prairie in a few years. It also invades roadsides, pastures, streambeds, and sand prairies.

European Cranberry-bush Viburnum opulus

Upright, spreading shrub that grows up to 15’ tall and wide. Its maple-shaped leaves are glossy dark green. They may remain green until they drop in fall or change to yellow- red or purple-red. Bright red, berry- like fruits ripen in fall and persist into winter.

Native to Europe, this plant was introduced in the second half of the 17th century for its ornamental qualities as well as its adaptability to many conditions.

Seeds are widely distributed by birds.

This prolific plant is starting to naturalize in wetlands and forests as well as degraded woodlands near urban and suburban areas, where it is displacing native species.