Ohio gardeners face a hidden threat that can wreak havoc on local ecosystems and native plant communities. Invasive perennials might look pretty in catalogs, but they can quickly take over gardens and spread into natural areas, choking out beneficial native species.
Knowing which plants to avoid can save you years of battling aggressive spreaders while helping protect Ohio’s natural biodiversity.
1. Purple Loosestrife
Once a popular garden plant, purple loosestrife now terrorizes wetlands across Ohio. A single plant can produce over two million seeds annually, creating dense stands that crowd out native vegetation vital to wildlife.
Recognizable by its tall purple flower spikes that bloom in summer, this aggressive invader alters water flow and degrades habitat quality. Several states have banned its sale, and Ohio actively works to control existing populations.
2. Japanese Knotweed
Bamboo-like stalks shooting up seemingly overnight mark the arrival of Japanese knotweed. This aggressive invader can grow through concrete, damage foundations, and lower property values.
Originally brought to America as an ornamental, knotweed forms impenetrable thickets reaching 10 feet tall. Its extensive root system can spread 65 feet horizontally and requires years of persistent treatment to eliminate once established in your yard.
3. Dame’s Rocket
Deceptively similar to native phlox, Dame’s rocket tricks many gardeners with its fragrant purple flowers. Look closer – phlox has five petals while this impostor sports four, a telltale sign of its invasive identity.
Dame’s rocket escapes gardens with remarkable efficiency, producing thousands of seeds that establish quickly in woodlands. The plant forms dense colonies that prevent tree seedlings from growing, gradually transforming diverse forests into monoculture stands.
4. Common Reed (Phragmites)
Towering up to 15 feet tall, common reed creates an intimidating presence in wetlands and ditches. The feathery plume-topped grass spreads aggressively through both seeds and underground rhizomes, forming dense stands that eliminate native plants.
Wildlife value plummets where phragmites invades, as the plant offers little nutritional benefit to native species. Even worse, it alters hydrology and can increase fire risk in wetland areas due to its abundant dry material.
5. Burning Bush
Fall’s spectacular red foliage makes burning bush a tempting addition to landscapes, but don’t be fooled by its seasonal show. Birds spread its abundant berries into natural areas where seedlings quickly establish and outcompete native understory plants.
Several states have banned this Asian shrub due to its aggressive nature. For Ohio gardens, native alternatives like Virginia sweetspire or blackhaw viburnum offer similar autumn color without the ecological damage.
6. Multiflora Rose
Armed with vicious curved thorns, multiflora rose forms impenetrable thickets that can engulf entire fields. Originally planted as living fences for livestock containment, this aggressive rose escaped cultivation decades ago.
A single plant produces up to a million seeds annually that remain viable in soil for years. Birds spread the bright red rose hips far and wide, creating new infestations. The thorny branches tear clothing, scratch skin, and make removal particularly challenging.
7. Garlic Mustard
Seemingly innocent with its small white flowers, garlic mustard ranks among Ohio’s most destructive woodland invaders. This biennial herb releases chemicals into the soil that prevent native tree seedlings from growing properly.
Early settlers brought it for food and medicine, unaware of its aggressive nature. Left unchecked, it forms dense carpets across forest floors within just a few seasons. Spring is the best time for removal, before plants set thousands of seeds.
8. Japanese Honeysuckle
Fragrant flowers might make Japanese honeysuckle seem like a garden dream, but this vine quickly becomes a nightmare. Capable of growing 30 feet in a single season, it smothers trees and shrubs under its twining mass.
Birds spread the black berries widely, creating new invasions in natural areas. The semi-evergreen leaves give it an advantage over native plants, allowing it to photosynthesize earlier in spring and later in fall than competitors.
9. Yellow Flag Iris
Striking yellow blooms make this water-loving iris particularly deceptive. Many gardeners plant it near ponds without realizing its aggressive nature and toxic properties.
Yellow flag iris forms dense colonies along shorelines, displacing native wetland plants vital to wildlife. The thick root systems alter water flow and sedimentation patterns in streams. Even handling the plant can cause skin irritation for some people.
10. Lesser Celandine
Spring’s golden carpet of lesser celandine might look cheerful, but it spells disaster for native wildflowers. This aggressive ground cover emerges earlier than native species, stealing light, nutrients, and space.
Lesser celandine reproduces through numerous small bulblets and tubers that break off easily during removal attempts. Even tiny fragments left behind quickly regrow. Once established in moist woodland areas, it can completely dominate the forest floor within a few seasons.
11. Chinese Silver Grass
Graceful plumes and variegated foliage make Chinese silver grass (Miscanthus) a popular ornamental grass. Unfortunately, its beauty masks its invasive potential, especially newer cultivars that produce viable seeds.
Wind carries the fluffy seeds far from parent plants, establishing new colonies in natural areas. The dense root systems outcompete native vegetation. Fire risk increases wherever this grass establishes, as its dry foliage ignites easily and burns hot.
12. Crown Vetch
Originally planted to control roadside erosion, crown vetch quickly escaped cultivation. The pink-flowered legume spreads rapidly through both seeds and underground stems, forming dense mats that smother native vegetation.
Don’t be fooled by its pretty flowers or erosion control benefits. Crown vetch alters soil chemistry through nitrogen fixation, creating conditions that favor other invasive species. Its extensive root system makes complete removal extremely difficult once established.
13. Oriental Bittersweet
Fall wreaths often feature oriental bittersweet’s bright orange berries, unwittingly spreading this destructive vine. Unlike our native American bittersweet, the oriental variety grows with aggressive abandon, girdling and eventually killing trees.
Birds spread the colorful berries, creating new infestations in forests and natural areas. The vine can completely blanket native vegetation, blocking sunlight and eventually causing collapse under its weight. Even small fragments of root can regenerate into new plants.