By Tom Adair, Park Services Director

Lake Metroparks has ramped up its invasive plant species management efforts considerably over the last few years. As part of its primary mission, Lake Metroparks is charged with conserving and preserving the natural resources of Lake County.

In recent decades, non-native and invasive plant species have threatened native plant communities by displacing them. This crowding out of native species can lead to monocultures (areas in which one plant species tends to predominate the entire landscape). A monoculture is characterized by very low biodiversity. Plant diversity is important for wildlife habitat as many animals depend on a variety of native plants for food and shelter.

There are more than 100 state listed (endangered, threatened or special interest) plant and animal species that have been identified within Lake Metroparks. These species are under particular stress as a result of expanding invasive plant populations.           

As part of its resource management practices, the park district has made a regular practice of identifying, monitoring and prioritizing management recommendations on these invasive plant populations. Once prioritized, management actions are implemented. Staff members from several departments within Lake Metroparks employ a combination of physical and chemical treatments to manage these infestations. Over the years, a number of very dedicated volunteers have also been instrumental in helping the parks to mage invasive plants.

According to the Ohio Division of Natural Areas and Preserves, “there are about 3,000 species of plants that have been identified in the wild in Ohio. Of these, about 75 percent are native or have occurred in Ohio before the time of substantial European settlement around the year 1750. The other 25 percent (around 700 to 800 species) are not native to our state, having been introduced from outside of Ohio and from around the world.”

Many of these species were originally introduced into gardens, cities and agricultural land and may never spread enough to threaten native plants. However, there are a few species that become very invasive and compete with native plants in forests, meadows, wetlands, stream corridors and other natural areas. Although some non-native invasive species are introduced by accident, others have been introduced for applications in erosion control, horticulture, crop production and medicine.

Well intending people also plant non-native plants for backyard wildlife watching or landscaping without realizing the negative impacts that may result from escape into natural areas. A lack of natural predators or biological controls will cause the plants to spread rapidly and displace native plants.

The following are a few of the more common terrestrial and aquatic non-native invasive plant species with general descriptions from the Ohio Division of Natural Areas and Preserves.

Japanese knotweed

Japanese knotweed (Polygonum cuspidatum) is a shrub-like herd that grows up to ten 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. Japanese knotweed can grow in a wide variety of habitats. It is found in open areas like roadsides, stream banks and woodland edges. It spreads quickly and forms dense thickets.

Common reed

Common reed (Phragmites australis) or phragmites, is a grass that reaches up to 15 feet in height. The leaves are smooth, stiff and wide with coarse hollow steams. 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). Common reed grows in open wetland habitats and ditches. It occurs in still water areas of marshes, lake shores, riverbanks and disturbed or polluted soils, often creating pure stands.

Reed canary grass

Reed canary grass (Phalaris arundinacea) is a large coarse grass that reaches two to five feet tall. The hairless stems gradually taper to flat and rough leaf blades three to ten 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). This grass occurs in wetlands like marshes, wet prairies meadows, fens, stream banks and seasonally wet areas. Reed canary grass has been panted widely for forage and erosion control.

Bush honeysuckle

Bush honeysuckles (Lonicera sp.) are upright shrubs that can grow six to 15 feet in height. Each has dark green egg-shaped leaves. The tubular flowers are white on the Amur honeysuckle and the Morrow’s honeysuckle (changing to yellow with age), and pink on the Tatarian honeysuckle. Berries range from red to orange, occasionally yellow, and are eaten and dispersed by birds. The bush honeysuckles inhabit abandoned fields, roadsides, woodlands and edges of marshes.

Garlic mustard

Garlic mustard (Alliaria petiolata) 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, then dies. First-year rosettes consist of kidney-shaped, garlic-smelling leaves; the second-year plant grows a stem up to four 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 that can remain viable for seven years or more. This woodland plant prefers some shade but is occasionally found in full sun. It invades upland and floodplain forest, savannas, yards, streams, trails and roadsides.

Purple loosestrife

Purple loosestrife (Lythrum salicaria) is a popular garden flower that grows three to seven feet tall and has a dense bushy growth of one to 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 one million seeds per plant. Supposedly sterile strains of L. virgatum will outcross with this plant and produce seeds. Purple loosestrife grows in a variety of wetland habitats including marshes, river banks ditches, wet meadows and edges of water bodies. Loosestrife can invade both natural and disturbed wetlands, replacing native vegetation with nearly pure stands of loosestrife.

Multiflora rose

Multiflora rose (Rosa multiflora) is a dense spreading shrub with widely arching canes and stuff curved thorns. This shrub grows up to 15 feet tall with alternate compound leaves of seven to nine leaflets. Multiflora rose has numerous white flowers that produce clusters of small red fruits. The fruits (hips) are eaten by birds and mammals which helps disperse the seeds. An individual plant can produce up to 500,000 seeds per year 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 by prefers sunny areas with well-drained soils.

Buckthorn

Buckthorns (Rhmanus sp.) 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. Glossy buckthorn usually occurs in wetlands, such as fens or bogs, but is also found 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.