Ohio's Invasive Non-Native Plants
Of the approximately 3,000 species of plants known to occur in the wild in Ohio, about 75 percent are native or have occurred in Ohio before the time of substantial European settlement, about 1750. The other 25 percent, around 700 to 800 species, are not native to Ohio, having been introduced from other states or countries.
Most of these species never stray far from where they are introduced (gardens, urban areas, agricultural fields), yet some become very invasive and displace native plants in woodlands, wetlands, prairies, and other natural areas. Non-native plants have been introduced for erosion control, horticulture, forage crops, medicinal use, and wildlife foods as well as simply by accident!
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| Amur honeysuckle |
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| Autumn olive |
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| Common buckthorn |
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| Common reed |
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| Garlic mustard |
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| Glossy buckthorn |
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| Japanese honeysuckle |
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| Japanese Knotweed |
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| Morrow honeysuckle |
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| Multiflora rose |
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| Purple loosestrife |
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| Reed canary grass |
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| Tatarian Honeysuckle |
Sometimes we plant non-native plants for landscaping or wildlife habitat without realizing the problems they may cause when they escape into natural areas. Without natural predators or controls, invasive non-native plants are able to spread quickly and force out native plants. In Ohio, several non-native plants are invading woodlands and displacing native spring wildflowers. Other non-native plants are impacting our wetlands by creating monocultures. Native plant diversity is important for wildlife habitat as many animals depend on a variety of native plants for food and cover.
This page describes ten of the most invasive non-native plant species in Ohio with information about their appearance, habitat, possible controls, and native species which can be used as alternatives in garden or wildlife plantings. Be aware that management of these invasive species is difficult and complex; obtain more detailed information before using controls such as herbicides.
JAPANESE HONEYSUCKLE
Lonicera japonica
Description: Japanese honeysuckle is a woody semi-evergreen vine with opposite, oval leaves. The flowers grow in pairs, are white to yellow, and very fragrant. Fruits, also in pairs, are purple to black berries. This vine climbs and drapes over native vegetation, forming dense patches.
Habitat: Japanese honeysuckle thrives in disturbed habitats, such as roadsides, trails, fencerows, abandoned fields, and forest edges primarily in southern Ohio. Disturbances such as logging, road building, floods, and windstorms create an opportunity for this vine to invade native plant communities.
Management: Burning in combination with systemic herbicide application may be an effective control method. Herbicides can be applied to the leaves when native plants are dormant. Be aware there are native climbing honeysuckles in Ohio, such as Lonicera dioica.
Native Alternatives: Virginia creeper (Parthenocissus quinquefolia), wild honeysuckle (Lonicera dioica), and virgin's bower (Clematis virginiana)
JAPANESE KNOTWEED
Polygonum cuspidatum
Description: This shrub-like herb grows up to 10 feet tall. Stems are smooth and the pointed leaves vary from broadly oval to almost triangular. Flowers are greenish-white and very small. The seeds are dispersed by wind. Once established, the plants spread by a system of underground stems reaching 60 feet.
Habitat: Japanese knotweed can grow in a wide variety of habitats. It is found in open areas, such as roadsides, streambanks, and woodland edges, primarily in eastern Ohio. It spreads quickly and forms dense thickets.
Management: Knotweed is very difficult to control. Leaves may be sprayed or stems cut and treated with systemic herbicide.
Native Alternatives: Japanese knotweed is not generally planted, however consider using northern arrowwood (Viburnum dentatum), black haw (Viburnum prunifolium), dogwoods (Cornus racemosa, C. amomum and C. sericea), and chokeberry (Aronia prunifolia, A. melanocarpa)
AUTUMN-OLIVE
Elaeagnus umbellata
Description: Autumn-olive is a fast-growing shrub or small tree reaching up to 20 feet tall. Its leaves are small and oval, dark green on the upper surface and silvery below. Small coppery dots occur on stems and leaves. This shrub has light yellow, aromatic flowers and produces large quantities of small, round red fruits that are readily eaten and spread by birds.
Habitat: Autumn-olive can survive in very poor soils because of its nitrogen-fixing root nodules. It grows in disturbed areas, roadsides, pastures, and fields throughout Ohio.
Management: Stems may be cut and treated with systemic herbicide. Resprouting will occur, so follow-up control is necessary. A combination of hand-pulling, digging and herbicide treatments is usually necessary.
Native Alternatives: black haw (Viburnum prunifolium), dogwoods (Cornus racemosa, C. amomum and C. sericea), and serviceberry (Amelanchier arborea)
BUCKTHORNS
Rhamnus frangula, R. cathartica
Glossy (or Shining), Common (or European) buckthorn
Description: Buckthorns are tall shrubs or small trees that grow up to 20 feet tall. The smooth, gray to brown bark is distinctively spotted. Glossy buckthorn has shiny leaves with smooth edges. It has solitary red to purple berry-like fruits. Common buckthorn has black fruits and dull green smooth leaves. Both species are abundant seed producers.
Habitat: Glossy buckthorn usually occurs in wetlands, such as fens or bogs, but it is also found in forests, fencerows, edges, prairies, and old fields. Common buckthorn occurs in a range of upland habitats, such as forests, woodland edges, fencerows, prairies, and old fields. Both species are most prevalent in central and northern Ohio.
Management: Cutting and treating stumps with systemic herbicide is the best method of control. Buckthorns are very difficult to control due to vigorous resprouting and a large seedbank.
Native Alternatives: lance-leaved buckthorn (Rhamnus lanceolata), winterberry (Ilex verticillata), dogwoods (Cornus racemosa, C. amomum and C. sericea), and white cedar (Thuja occidentalis)
PURPLE LOOSESTRIFE
Lythrum salicaria
Description: This popular garden flower grows 3-7 feet tall and has a dense bushy growth of 1-50 stems. Long spikes of flowers are purple to magenta; linear-shaped leaves grow opposite along the square stems. Purple loosestrife spreads aggressively by underground stems (rhizomes) and can produce as many as a million seeds per plant. Supposedly sterile strains of L. virgatum will outcross with this plant and produce seeds.
Habitat: Purple loosestrife grows in a variety of wetland habitats including marshes, river banks, ditches, wet meadows, and edges of water bodies, primarily in northern Ohio. Loosestrife can invade both natural and disturbed wetlands, replacing native vegetation with nearly pure stands of loosestrife.
Management: Small stands of purple loosestrife can be controlled by hand-pulling, digging, or applying systemic herbicides to the foliage. Herbicides may be used to control large populations. Biological controls using insects are being researched in Ohio and other states and may be helpful in reducing infestations.
Native Alternatives: spiked blazing-star (Liatris spicata), blue lobelia (Lobelia siphilitica), cardinal flower (Lobelia cardinalis), rose mallow (Hibiscus moscheutos), and blue flag iris (Iris versicolor)
COMMON REED OR PHRAGMITES
Phragmites australis
Description: Common reed, or Phragmites, is a grass that reaches up to 15 feet in height. The leaves are smooth, stiff and wide with coarse hollow stems. The big, plume-like flower head is grayish-purple when in fruit. Common reed spreads mostly vegetatively forming huge colonies by sprouting new shoots through underground stems (rhizomes).
Habitat: Common reed grows in open wetland habitats and ditches primarily in northern Ohio. It occurs in still water areas of marshes, lake shores, riverbanks, and disturbed or polluted soils, often creating pure stands. Some populations are not invasive and may be native, however there is no reliable method to tell the two apart.
Management: Long-term management is necessary for control of this persistent plant. Cutting and/or treating stems with systemic herbicides is generally the most effective, grass-specific herbicides are recommended in areas where native plants occur.
Native Alternatives: Indian grass (Sorghastrum nutans), big bluestem (Andropogon gerardii), prairie cord grass (Spartina pectinata), and Canada bluejoint (Calamagrostis canadensis)
REED CANARY GRASS
Phalaris arundinacea
Description: This large, coarse grass reaches 2-5 feet tall. The hairless stems gradually taper to flat and rough leaf blades 3-10 inches long. The flowers occur in dense clusters and are green to purple, changing to beige and becoming more open over time. The plant spreads aggressively both by seed and by forming a thick system of underground stems (rhizomes).
Habitat: This grass occurs in wetlands, such as marshes, wet prairies, meadows, fens, stream banks, and seasonally wet areas throughout Ohio. Reed canary grass has been planted widely for forage and erosion control. Native strains possibly occur, however introduced strains are thought to be more invasive. There is no reliable method to tell the two strains apart.
Management: A combination of burning or mowing with systemic herbicides is the best method of control; grass-specific herbicides applied with wick applicators are recommended in areas where native plants occur.
Native Alternatives: Reed canary grass is not generally planted, however consider using prairie cord grass (Spartina pectinata) and Canada bluejoint (Calamagrostis canadensis).
GARLIC MUSTARD
Alliaria petiolata
Description: Garlic mustard is a biennial herb. It begins as a rosette of leaves in the first year, overwinters as a green rosette of leaves, flowers and fruits in the second year, and then dies. First-year rosettes consist of kidney-shaped, garlic-smelling leaves, the second-year plant grows a stem up to 4 feet tall with triangular, sharply-toothed leaves. The small, four-petaled flowers are white and grow in clusters at the top of the stem. Garlic mustard produces large quantities of seeds which can remain viable for seven years or more.
Habitat: This woodland plant prefers some shade but is occasionally found in full sun. It invades upland and floodplain forests, savannas, yards, streams, trails, and roadsides throughout Ohio.
Management: Repeated prescribed burns in oak forests may be effective. Light infestations of garlic mustard can be hand pulled before or at flowering time. Plants should be removed from the site after pulling as the seeds may continue to mature. Systemic herbicides can be applied to the rosettes in early spring or late fall.
Native Alternatives: Garlic mustard is not generally planted, however consider using white baneberry (Actaea pachypoda), columbine (Aquilegia canadensis), blue phlox (Phlox divaricata), and black cohosh (Cimicifuga racemosa)
MULTIFLORA ROSE
Rosa multiflora
Description: Multiflora rose is a dense spreading shrub with widely arching canes and stiff, curved thorns. This shrub grows up to 15 feet tall with alternate, compound leaves of seven to nine oval leaflets. Multiflora rose has numerous white flowers that produce clusters of small, red fruits. The fruits (called hips) are eaten by birds and mammals which help disperse the seeds. An individual plant can produce up to 500,000 seeds per year!
Habitat: Multiflora rose was formerly planted as a "living fence" to control livestock, stabilize soil and create barriers for roadways. It has also been planted as a wildlife cover and food source. This rose occurs in a wide range of habitats throughout Ohio but prefers sunny areas with well-drained soils.
Management: A long-term management program of mowing or cutting and treating stems with systemic herbicide several times during the growing season is recommended. Digging or hand-pulling small shrubs may also be effective.
Native Alternatives: Carolina rose (Rosa carolina), black haw (Viburnum prunifolium), swamp rose (Rosa palustris), fragrant sumac (Rhus aromatica), and smooth rose (Rosa blanda)
BUSH HONEYSUCKLES
Lonicera maackii, L tatarica, L. morrowii
Amur, Tatarian, Morrow's honeysuckle
Description: These upright shrubs can grow 6-15 feet in height. Each have dark green, egg-shaped leaves. The tubular flowers are white on the Amur and the Morrow's (changing to yellow with age), and pink on the Tatarian. Berries range from red to orange, occasionally yellow, and are eaten and dispersed by birds.
Habitat: The bush honeysuckles inhabit abandoned fields, roadsides, woodlands, and edges of marshes. Although they may be concentrated in one part of the state or another, all three species can be found throughout Ohio.
Management: The best control method is to cut and treat stumps with systemic herbicide. Sprouts from cut stems may be treated with a foliar application of systemic herbicide. Young shrubs are easy to pull or dig up. Be aware there is a native bush honeysuckle in Ohio (Diervilla lonicera).
Native Alternatives: nine-bark (Physocarpus opulifolius), dogwoods (Cornus racemosa, C. amomum and C. sericea), northern arrowwood (Viburnum dentatum), winterberry (Ilex verticillata), and chokeberry (Aronia prunifolia, A. melanocarpa)
WHAT YOU CAN DO TO HELP:
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Be careful not to gather and transport unidentified seeds which may spread invasive plants.
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Avoid disturbance to natural areas, including clearing of native plants and dumping of yard wastes.
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Start early! Early detection and control makes eradication efforts much easier!
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