Invasive Plants & Treatment

Invasive Plants & Treatment

There is a great deal of information available for the identification and treatment of invasive plant species. Below, we’ve provided identification and treatment information for the most common invasive plant species found around Muskegon Lake. Before deciding to treat a plant, make sure you can properly identify it, identify the surrounding plants, and choose the appropriate technique. It’s also important to get the permission of landowners or neighbors as needed, and to obtain any necessary permits for the treatments.

Always work within your skill set, and never, ever remove or treat a plant if you don’t know what it is.

The Midwest Invasive Species Information Network is an amazing resource for the identification and recommended treatments of invasive species.

MISIN | Midwest Invasive Species Information Network

Tree of Heaven – Ailanthus altissima

Overview: Tree-of-Heaven is a fast growing, robust, smooth-barked deciduous tree that is native to China. With an average height of 40-65 feet and 2-40 inch diameter, this allelopathic invasive plant is found in fields, meadows, shores, and riverbanks, and can also be found in yards, on roadsides, and beside walls and buildings.

Recommended Management: For mature trees, use cut-stump treatments and apply a 75-100% glyphosate-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Herbicide should only be applied by a trained and knowledgeable steward who holds a commercial applicator’s license from the State of Michigan if the work is completed for hire. All work should be completed according to federal, state and local regulations and according to the herbicide label. Exercise caution and selectivity in both the choice of herbicide and the application technique.

Garlic mustard Alliaria petiolata

Overview: Garlic mustard is a ground dominant plant found in the understory of forests and is a native of Europe and Asia. This weedy invasive biennial can grow up to 3 feet tall and can be found in upland and floodplain forested areas as well as along trails, roadsides and disturbed areas. It smells like garlic when crushed and has numerous small, white colored flowers that bloom in late April through June.

Recommended Management: Garlic mustard can be hand-pulled in April and May, prior to flowering. The plants can also be treated with a foliar application of a 2% glyphosate or triclopyr-based herbicide solution in April or May, prior to flowering.

Japanese barberry – Berberis thunbergii

Overview: Japanese barberry is a common plant used for hedges that frequently escapes into forests, swamps, fields, and dunes and is a native species of Asia. Its leaves grow in small oval like clusters and its stems have reddish bark on the outside and bright yellow bark on the inside. This spiny shrub grows 2-3 feet tall and has small bright red berries that are often dispersed by birds.

Recommended Management: For mature shrubs, use cut-stump treatments and apply a 75-100% glyphosate-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Oriental bittersweet – Celastrus orbiculatus

Overview: Oriental bittersweet is a woody deciduous twining vine that can smother trees and shrubs and is a native of Asia. This glossy round leaved invasive can climb 60 feet high in trees and can reach 4 inches in diameter. It is often found in forests, along pathways, woodland edges, and roadsides. This plant is extremely aggressive when it escapes cultivation and can girdle other trees making it a threat to native species.

Recommended Management: For mature vines, use cut-stump treatments and apply a 75-100% glyphosate-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Spotted knapweed – Centaurea stoebe

Overview: Spotted knapweed is a noxious biennial or perennial weed that can spread aggressively along roadsides, rights-of-way, fields, prairies, dunes, and beaches. This European invader has grayish green leaves and can grow 2-4 feet tall. Its bright purple-pink flower can be easily seen in places where it takes over open sites.

Recommended Management: Small populations of spotted knapweed can be hand-pulled in May and June, prior to flowering. Larger infestations can also be treated with a foliar application of a 2% glyphosate or triclopyr-based herbicide solution.

Canada thistle – Cirsium arvense

Overview: Canada thistle is a noxious perennial weed that is native to Europe. It is often found along roadsides, ditches, disturbed open areas, prairies, and sometimes swampy areas. This invasive species has a purple-lavender flower and can grow in large monocultures to a height of 2 – 5 feet. Seeds from this plant can persist in the seed bank for 20 years.

Recommended Management: Canada thistle should be treated with a foliar application of a 2% glyphosate or triclopyr-based herbicide solution in May-August. This species can reproduce from root fragments and is difficult to eradicate so multiple applications per year may be required.

Japanese knotweed ~ Fallopia japonica

Overview: Japanese knotweed is a perennial herbaceous shrub that can be found along roadsides, ditches, wetlands, stream and riverbanks, woodland edges and is native to Japan. This invasive species has round hallowed steams similar to bamboo, larger 5 inch diameter leaves, white-green flowers and can grow up to 10 feet tall. Once this plant has established it is very difficult to eradicate because of its rhizomatous reproductive behavior.

Recommended Management: Japanese knotweed is persistent, difficult to control, and may require several years of treatments to manage. This species should be treated with a foliar application of a 2% glyphosate or triclopyr-based herbicide solution in May-August. Multiple applications per year may be required.

Bull thistle – Cirsium vulgare

Overview: Bull thistle is a biennial (sometimes annual), spiny, prickly, hairy, noxious weed that can be found along roadside ditches, open fields and clearings, and near disturbed sites. It is a native to Europe, western Asia, and northern Africa. This species has lace shaped spiny leaves and purple flowers. It can grow to a height of 6.5 feet and has a taproot that can grow up to 28 inches long.

Recommended Management: Bull thistle should be treated with a foliar application of a 2% glyphosate or triclopyr-based herbicide solution in May-August. Targeted mowing over multiple seasons may also be used to prevent seeding and reduce populations.

Autumn olive – Elaeagnus umbellata

Overview: Autumn olive was originally planted as an ornamental and for wildlife habitat but quickly became an invader. This species can out-compete native species and can increase nitrogen levels in the soil which may be detrimental to native plants. Autumn olive is a deciduous shrub and can grow to the size of a small tree, 20 feet in height and sometimes 30 feet wide. Branches and stems are often thorny, and its oval leaves are silvery underneath.

Recommended Management: For mature shrubs, use cut-stump treatments and apply a 75-100% glyphosate or triclopyr-based herbicide to the open wound any time between May and March. For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Glossy buckthorn – Frangula alnus

Overview: Glossy buckthorn is a deciduous shrub or small tree that can be an aggressive pest. Growing in a variety of soil types ranging from very dry soils to wetland habitats, it is native to Europe and Asia. It can be found along power lines and clearings, along pathways, and around woodland edges. This species creates large thickets and can grow up to 20 feet tall with a trunk diameter up to 10 inches.  Glossy buckthorn has prominent lenticels which results in spotted looking stems.

Recommended Management: For mature trees, use cut-stump treatments and apply a 75-100% glyphosate or triclopyr-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Herbicide should only be applied by a trained and knowledgeable steward who holds a commercial applicator’s license from the State of Michigan if the work is completed for hire. All work should be completed according to federal, state and local regulations and according to the herbicide label. Exercise caution and selectivity in both the choice of herbicide and the application technique.

Common privet – Ligustrum vulgare

Overview: Common privet is a stout, bushy shrub that is sometimes used as an ornamental. It often grows in disturbed forests and grasslands with either dry or moist soils, and is a native of Europe. This species can grow to heights ranging from 12 to 15 feet tall, and has simple, opposite, ovate leaves that can grow 1-3 inches long with a dark green tint on top and paler underside. The stems of this plant can often be spiny but gradually become smooth overtime.

Recommended Management: For mature shrubs, use cut-stump treatments and apply a 75-100% glyphosate or triclopyr-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Honeysuckle species – Lonicera spp.

Overview: Various honeysuckle species are found within the Muskegon Lake watershed, each fairly similar to one another. This deciduous shrub can grow up to 6 feet tall, is found in various soil and moisture conditions, grows along roadsides and within disturbed areas, and can take over native plant communities. Honeysuckle has traditionally been recommended for wildlife habitat, but its invasive nature makes it a pest to native species. This plant creates large thickets, which reduces tree and shrub regeneration resulting in a decline of plant diversity.

Recommended Management: For mature shrubs, use cut-stump treatments and apply a 75-100% glyphosate or triclopyr-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Purple loosestrife – Lythrum salicaria

Overview: Purple loosestrife is a persistent, herbaceous, perennial, wetland weed that can spread vigorously in moist soil conditions. This species is attractive for its intensely purple flower but can outcompete native plant communities. It can grow 1-6 feet tall with distinguishable whorled and somewhat clasping leaves. Purple loosestrife can invade entire wetland areas resulting in decreased biodiversity.

Recommended Management: Purple loosestrife is one of the few invasive plant species in Michigan where biological control can be used as a treatment method. Galerucella beetles can be released to help reduce large populations. Purple loosestrife can also be treated with a foliar application of a 2% glyphosate or triclopyr-based herbicide solution in August-September.

White sweet-clover – Melilotus albusa

Overview: White sweet-clover is an herbaceous annual or biennial and can be found in disturbed sites, along roadsides, and in calcareous soil conditions such as sand dunes and prairies. This species can grow up to 5 feet tall with numerous branched, leafy stems and flowers white in color along the end of the stem. It can often look bushy because of the large number of leafy stems that spread near the base of the plant.

Recommended Management: Smaller populations can be hand-pulled before flowering and larger populations can be selectively mowed over multiple growing seasons.

Reed canary grass – Phalaris arundinacea

Overview: Reed canary grass is a cool season perennial grass that forms dense monocultures in wet soil conditions along marshes, streams, ponds, and ditches. These large cluster monocultures form a thick mat of rhizomes and choke out native vegetation resulting in decreased biodiversity. Reed canary grass can grow 2-8 feet tall, has flat rough leaves, and a has prominent ligule that can be a great tool for identification. This grass is becoming a major problem in wetlands across southern Michigan.

Recommended Management: Reed canary grass should be treated with a foliar application of a 2% glyphosate-based herbicide solution in May-August. This species is difficult to control and follow up treatments my be required for 5-10 years.

Common reed – Phragmites australis sub sp. austrails

Overview: Common reed, also known as Phragmites, forms dense monocultures and is an aggressive invader to wetlands, marshes, and the Lake Michigan shoreline. Impenetrable phragmites stands can colonize along roadsides and highways and can grow up to 15 feet tall. Identification traits include smooth greenish-gray leaves and a distinct hairy. Phragmites can spread through thick mats of lateral rhizomes and has a puffy seed plume and hollow stem that persists through winter. Phragmites invasion is a major problem in southern and eastern Michigan.

Recommended Management: Phragmites should be treated with a foliar application of a 2% glyphosate-based herbicide solution in late August-October. In some situations, phragmites can also be controlled through hydrological alteration by raising water levels and drowning infestations.

Common buckthorn – Rhamnus cathartica

Overview: Common buckthorn is a deciduous woody pest that forms thickets along woodland edges, roadsides, railroads, riverbanks, and old fields. This plant is sometimes used as an ornamental and planted in hedgerows, but has naturalized since its introduction and is now a major threat to native communities. Common buckthorn, not to be mistaken with glossy buckthorn, has smooth and shiny leaves that are dark green in color as well as orange inner bark. Stems are brown to gray in color with dotted lenticels. Common buckthorn can grow to a height of 10-25 feet tall.

Recommended Management: For mature trees, use cut-stump treatments and apply a 75-100% glyphosate or triclopyr-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Multiflora rose – Rosa multiflora

Overview: Multiflora rose is a perennial shrub with long, arching thorny branches and can be found in disturbed forests and along roadsides and fencerows. It can grow 16 feet tall, 9-23 feet wide, and in a variety of soil conditions. The white flowers have 5 petals and its red fruits are distinguishable late in the season. Multiflora rose was first thought to be a valuable plant in preventing erosion and producing food for wildlife, but is now recognized as an invasive threat.

Recommended Management: For mature shrubs, use cut-stump treatments and apply a 75-100% glyphosate or triclopyr-based herbicide to the open wound any time between May and March (not spring sap flow). For smaller species, a 3-5% solution of a glyphosate or triclopyr-based herbicide may be applied after full leaf-out.

Narrow-leaved cattail – Typha angustifolia

Overview: Narrow-leaved cattail inhabit wet to intermittently wet conditions and can be found in wetlands, marshes, ditches, streams, and along the Lake Michigan shore. This emergent perennial can grow 4-10 feet tall with flat, narrow, dark green leaves and a brown clustered flower.  Narrow-leaved cattail can be dominant in marshes and wetlands across Michigan.

Recommended Management: Narrow-leaved cattails should be treated with a foliar application of a 2% glyphosate-based herbicide solution in July-September. In some situations, cattails can also be controlled through hydrological alteration by raising water levels and drowning infestations.

Hybrid cattail – Typha x glauca

Overview: Hybrid cattail is a cross between narrowleaf cattail and broadleaf cattail. This emergent perennial can grow 5-10 feet tall, usually taller than narrowleaf and broadleaf cattail, and has more of a blue-green color. The female flower is dense and brown and grows below the lighter male. This plant can establish itself to take over wetlands and marshes and is more prominent along Lake Erie.

Recommended Management: Hybrid cattails should be treated with a foliar application of a 2% glyphosate-based herbicide solution in July-September. In some situations, cattails can also be controlled through hydrological alteration by raising water levels and drowning infestations.

Herbicide should only be applied by a trained and knowledgeable steward who holds a commercial applicator’s license from the State of Michigan if the work is completed for hire. All work should be completed according to federal, state and local regulations and according to the herbicide label. Exercise caution and selectivity in both the choice of herbicide and the application technique.