Kayla Clarke , Senior Web Producer
Kayla Clarke , Senior Web Producer
There are two invasive trees and seven invasive shrubs that Michigan officials want residents to be aware of.
The black locust tree was planted throughout the Midwest for erosion control, fence posts and fixing nitrogen in the soil but its leaves, stems, bark and seeds are toxic to horses.
Most of the shrubs are a concern because they will outcompete native plants for resources. Below I’ll go over the trees and shrubs that Michigan has listed online, how to identify them and what threat they pose to you or the ecosystem.
This fast-growing tree has been planted throughout the Midwest for erosion control, fence posts, and fixing nitrogen in the soil. It forms dense colonies that can harm native vegetation. It’s also toxic to horses.
It is established in Michigan and prefers sun and well-drained soils but will grow in poor soils and disturbed areas including roadsides, open fields and forest openings. It has been planted throughout the Midwest, West Coast and Texas for erosoin control, fence posts and fixing nitrogen in the soil.
Why is it a concern?
Black locust spreads by root suckering and stump sprouting, forming dense colonies that shade prairies and forest openings, harming native vegetation. Black locust leaves, stems, bark and seeds are toxic to horses.
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This fast-growing tree can reach up to 70 feet. It has been detected in Michigan. Its roots can damage sewers and structures, they also produce chemicals that inhibit the growth of other plants.
It has been detected in Michigan and can tolerate poor soils and drought but requires some sun. It can be found in old fields, forest edges and openings, and in urban environments where it was used in landscaping. It is widespread throughout most of the United States.
Why is it a concern?
Root shoots can develop into dense thickets. Roots can damage sewers and structures. Roots also produce chemicals that inhibit the growth of other plants.
Read: Let’s talk about Michigan’s invasive herbs: How to identify them and the threat they pose
This shrub can grow to 20 feet high and is established in Michigan.
It is moderately shade tolerant and occurs on a variety of soil types. It spreads rapidly in old fields and is also found in open woods, along forest edges, roadsides, sand dunes, and other disturbed areas.
Why is it a concern?
It was originally planted for wildlife food and habitat but it is highly aggressive. Its seeds are widely dispersed by birds and mammals. It can shade out native plants and fixes nitrogen in the soil, which can degrade native plant communities that thrive on low-nutrient soils. It is difficult to control because cut stumps and roots will resprout.
This small tree or shrub can reach 25 feet tall and is established in Michigan.
It can be found in disturbed and undisturbed areas like roadsides, pastures, old fields and woodlots.
Why is it a concern?
It spreads quickly and crowds out native shrubs and understory plants. It is a host for alfalfa mosaic virus and crown fungus, and may be a possible host for the soybean aphid.
This perennial and herbacious shrub can grow over 12 feet high and has been detected in Michigan.
It likes moist soils in sunny areas along roadsides, disturbed fields or vacant lots and along streams or river banks.
Why is it a concern?
Giant knotweed spreads aggressively by roots (rhizomes) and cut or broken stems. It can form dense thickets along streambanks, actually increasing erosion potential and decreasing habitat value.
This small tree or shrub can reach 18 feet tall and is established in Michigan.
It prefers sunlight in moist soils but can tolerate shade. It’s often found in wetlands, along fence rows, roadsides, open woods and in pastures.
Why is it a concern?
This invasive shrub is a threat to native plants in prairie fens and other ecologically important wetland communities. It is a host for alfalfa mosaic virus and crown fungus and may be a possible host for the soybean aphid.
This shrub is usually 1-2 feet tall, but can grow up to 6 feet in height. It’s established in Michigan.
It thrives in the sun or shade. It is often found in forests, pastures, and old fields. It can be found along woodland edges, roadsides, and disturbed areas.
Why is it a concern?
Japanese barberry is a common ornamental plant that can easily escape cultivation. Its seeds are dispersed by birds and wildlife. Plants are not browsed by livestock or wildlife due to thorns, giving it a competitive advantage over native plants. Shrubs form dense stands that displace native species. Japanese barberry can raise pH levels in soil.
This shrub can grow from 3 to 10 feet tall and is established in Michigan.
It can be found along roadsides, wetlands, wet depressions, woodland edges, and streams or river banks. It prefers full sun, but can tolerate some shade and a wide range fo soil and moisture conditions.
Why is it a concern?
Japanese knotweed grows very aggressively in disturbed areas. It excludes native plants by light limitation, nutrient cycling alterations and allelopathy (releasing toxic or inhibiting chemicals to suppress the growth of potential competitor plant species).
This shrub can grow up to 15 feet and is established in Michigan.
It is found in pastures, old fields, roadsides, forests, streambanks, and wetlands. It tolerates a broad range of soils and moisture conditions and can live in sun or shade.
Why is it a concern?
Multiflora rose spreads aggressively, both by rooting canes (ends of branches) and by seed dispersed by birds and wildlife. Dense thickets of this shrub crowd out beneficial shrubs and plants and may deter native birds from nesting.
You can visit Michigan’s invasive species website to learn more about these invasive trees, shrubs and other invasive species.
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Kayla is a Web Producer for ClickOnDetroit. Before she joined the team in 2018 she worked at WILX in Lansing as a digital producer.
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