Nearly a quarter of the plants growing wild in Ohio are not native to the state. While most of these 500-plus species live harmlessly alongside the native plants, the Ohio Department of Agriculture lists 63 invasive plant species. Invasive plants in Ohio threaten native plants and wildlife, especially endangered species, with their unchecked, aggressive growth. Diverse ecosystems quickly become monocultures when invasive species crowd out all other plants.
Unfortunately, many of these weeds can be found in gardens masquerading as ornamental plants. Learning how to identify some of the most common invasive plants in Ohio gardens can enable you to help fight their spread. By replacing invasive species with native alternatives, you can not only help control invasive plants but also nurture healthy ecosystems.
Common Invasive Plants in Ohio Gardens
If you recognize any of the following invasive plants on your property, consult your local Extension Office or the Ohio Invasive Plants Council for proper removal methods. Each description in the list below includes suggestions for similar native plants to grow instead.
1. Tree of heaven (Ailanthus altissima)
Growing up to 80 feet tall, tree of heaven has grayish bark and pinnately compound leaves with anywhere from 11 to 41 leaflets. Its large, terminal clusters of yellow-green flowers are followed on female trees by flat, twisted, winged seeds that may remain on the tree until fall. To differentiate this tree from sumac or black walnut, crush a leaf, break a twig, or scratch the bark. Tree of heaven gives off a strong, unpleasant odor.
Here are 4 effective control methods for tree of heaven.
Native staghorn sumac (Rhus typhina) has a very similar appearance, and yellow buckeye (Aesculus lava) also makes a nice alternative tree.
2. Flowering rush (Butomus umbellatus)
An aquatic perennial, flowering rush invades the margins of slow-moving waterways, such as streams, ditches, marshes, and vernal ponds. Its long, linear leaves grow from the rhizome and may be erect or floating on the water. From June to August, umbels of small, pale pink to white flowers bloom. Flowering rush grows one to five feet tall and forms stands dense enough to impede boat traffic.
Similar native aquatic plants include common rush (Juncus effusus) and common threesquare (Schoenoplectus pungens).
3. Asian bittersweet (Celastrus orbiculatus)
A fast-growing, woody vine, Asian bittersweet reaches lengths of 60 feet. The stems often have distinct lenticels and are covered in alternate, rounded, finely-toothed leaves. Clusters of small, greenish flowers bloom in leaf axils, followed by small, bright yellow fruits that split open to reveal three vibrant red-orange seeds.
American bittersweet (C. scandens) looks very similar but with elliptical leaves and flowers and fruit appearing at the tips of stems. Virginia creeper (Parthenocissus quinquefolia) is another good alternative, with blue berries and red fall foliage.
4. Autumn olive (Elaeagnus umbellata)
Autumn olive is a large shrub or small tree growing 20 to 30 feet tall. It has dark brown bark with silvery speckles and wavy, ovate leaves with distinctive silver undersides. In spring, small, fragrant, white to pale yellow flowers bloom in clusters. Red berries flecked with silver follow. The very similar Russian olive (E. angustifolia) is also invasive and can be distinguished by its dull green, egg- to lance-shaped leaves and yellow fruit.
Allegheny serviceberry (Amelanchier laevis) produces masses of white spring flowers followed by purple berries, and gray dogwood (Cornus racemosa) has white flowers, white berries with red stems, and pale undersides on the leaves.
5. Dame’s rocket (Hesperis matronalis)
A member of the mustard family, dame’s rocket is a biennial that grows up to four feet tall. Its rough, serrated, lanceolate leaves form a rosette in the first year of growth, and in the second year, it blooms from late April into early July. Ranging from white to purple, the small flowers grow in clusters on branched stems. Though it closely resembles phlox, dame’s rocket may be identified by its four-petaled flowers, whereas phlox flowers have five petals.
Native phlox species include Carolina phlox (Phlox carolina) and garden phlox (P. paniculata), both of which look very similar to dame’s rocket and make an excellent alternative.
6. Common privet (Ligustrum vulgare)
Common privet is a deciduous shrub in the olive family with small, glossy, oval to lance-shaped leaves and sometimes thorns. In summer, it produces panicles of creamy white tubular flowers, followed by green berries that ripen to dark purple or black. Birds often enjoy these berries, effectively spreading the seeds of this aggressive shrub.
The native shrubs black chokeberry (Aronia melanocarpa) and blackhaw (Viburnum prunifolium) both feature clusters of white flowers and purplish-black berries.
7. Japanese honeysuckle (Lonicera japonica)
A semi-evergreen vine, Japanese honeysuckle is well-known for its sweetly fragrant, tubular flowers that mature from white or pale pink to yellow. These flowers bloom in pairs along the stem from April through June and are followed by pulpy black fruit that ripen in fall. The small, ovate leaves persist into late winter or early spring, and the stems they grow on tend to be hairy and hollow.
Plant trumpet honeysuckle (L. sempervirens) instead, or choose another native flowering vine, like crossvine (Bignonia capreolata).
8. Bush honeysuckles (Lonicera maackii, L. morrowii, L. tatarica)
Collectively referred to as invasive bush honeysuckles, Amur, Morrow’s, and Tatarian honeysuckle are all upright, deciduous shrubs with pairs of fragrant, tubular spring flowers. They have opposite, ovate leaves with short petioles, or stalks, and their berries ripen to yellow or dark red in late summer or early autumn. Unlike native honeysuckles, these invasive species have hollow stems.
Native bush honeysuckles include Canada fly honeysuckle (L. canadensis) and northern bush honeysuckle (Diervilla lonicera), which looks very similar but actually belongs to a different genus.
9. Purple loosestrife (Lythrum salicaria)
An erect herbaceous perennial, purple loosestrife grows three to six feet tall. It has a long blooming period, from June to September, during which time it sends up tall spikes of magenta flowers. Its opposite to whorled leaves are lance-shaped and stalkless. Due to its considerable seed production, it forms dense stands in damp areas like wetlands and streambanks.
Winged loosestrife (L. alatum), a native species, has a very similar appearance but with a shorter stature, alternate leaves, winged stems, and more widely spaced flowers. Blazing star (Liatris spicata) also produces tall, showy spikes of purple flowers.
10. Reed canary grass (Phalaris arundinacea)
Reaching anywhere from two to seven feet high, reed canary grass also ranges in where it grows, from dry soil to standing water. Its rough, narrow leaves grow from hairless, upright stems. From May to mid-June, it produces compact panicles that start out green to purple and eventually fade to beige. Reed canary grass spreads via the shiny brown seeds that mature in late June as well as its thick rhizomatic root system.
Native grasses to grow instead include big bluestem (Andropogon gerardii) and switchgrass (Panicum virgatum).
11. Common buckthorn (Rhamnus cathartica)
Common buckthorn, a woody shrub to small tree, can grow up to 20 feet tall. The slender stems often have a spine at the tip, and the glossy, ovate leaves have serrated edges and tend to stay green well into the fall. Following small, yellow-green flowers, the fruit ripens to a deep purple-black between July and September. The very similar glossy buckhorn (Frangula alnus) is also invasive.
Native buckthorns can be planted instead, such as alder-leaved buckthorn (R. alnifolia) or lance-leaved buckthorn (R. lanceolata).
12. Siberian elm (Ulmus pumila)
Siberian elm is a deciduous tree 30 to 70 feet tall with slender, spreading branches that form an open, rounded crown. Its thin, silvery twigs appear to zig-zag, with a leaf bud on each bend. It has very small, elliptical leaves with a pointed tip, toothed margins, and an uneven base. Before the leaves develop in spring, drooping clusters of two to five greenish flowers bloom. Round, winged seeds follow.
Plant American elm (U. americana) instead, or choose another native deciduous tree, like black tupelo (Nyssa sylvatica).
Now that you can identify some of the most common invasive plants in Ohio gardens, it’s time to remove any you find from your yard and nurture some beautiful native plants instead. What a wonderful excuse to go plant shopping!
