5 invasive plants to watch out for in Michigan

Elaeagnus umbellata (Autumn Olive)

There are several types of plants that can cause trouble in Michigan.

The Michigan DNR says species that are not native and also have the potential to harm human health or to harm natural, agricultural or silvicultural resources can be listed as prohibited or restricted by the State of Michigan.

If a species is prohibited or restricted, it is unlawful to possess, introduce, import, sell or offer that species for sale as a live organism, except under certain circumstances.

Related: Worse than poison ivy: How to identify, report dangerous hogweed plant found in Michigan

Here are five Michigan plants to watch out for:

Common Buckthorn

Identification:

  • Deciduous small tree or shrub – can reach 25 feet tall
  • Leaves are dark- green, oval and slightly toothed
  • In spring, small, yellow-green, 4-petaled flowers grow in clusters of 2-6 at the base of leaves
  • Small, purple to black fruits ripen in the fall
  • Twigs often have a single, sharp thorn at their tip
  • Distinctive orange inner bark

Habitat: Common buckthorn can be found in disturbed and undisturbed areas including roadsides, pastures, old fields and woodlots. 

Native Range: Europe and Asia

U. S. Distribution:  East Coast and Midwest, also in limited areas of California and Oregon.

Local Concern: This invasive plant spreads quickly through seeds distributed by birds and wildlife 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.

Related: 11 invasive species to watch out for in Michigan

Giant Knotweed

Identification:

  • Perennial, herbaceous shrub that can grow over 12 feet high
  • Hollow stalks are light green, smooth and swollen at the nodes, resembling bamboo
  • Similar to Japanese knotweed, and the two plants may hybridize
  • Flowers are arranged in spikes near the end of the stem are small, numerous, and greenish-white in color
  • Flowers do not extend past the length of the leaves
  • Flowers bloom in August and September in Michigan
  • Giant knotweed leaves are 6-14 inches long, heart-shaped at the base and have fine hairs on the underside

Habitat: Giant knotweed can be found in moist soils in sunny areas along roadsides, disturbed fields or vacant lots and along streams or river banks. 

Native Range: Japan

U.S. Distribution: Areas of the northeast and northwest United States. Locations in Michigan’s Upper and Northern Lower peninsulas

Local 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.

Autumn Olive

Identification:

  • Deciduous shrub that can grow to 20 feet high
  • Leaves are bright green on top and distinctively silver underneath
  • Spring-blooming cream or yellow flowers have a strong fragrance
  • Abundant red berries are lightly speckled and easily seen in the fall
  • Flowers arranged in spikes near the end of the stem are small, numerous, and creamy white in color
  • Flowers bloom in August and September in Michigan

Habitat: Autumn olive 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. It poses a particular threat to prairies, savannas and open woods.

Native Range: Asia

U.S. Distribution:  Autumn olive is widespread throughout Michigan and the Eastern United States.  Smaller populations exist in Washington and Oregon.

Related: Gypsy moth outbreak poses risk to Michigan trees

Local Concern:  Historically planted for wildlife food and habitat, autumn olive has been found to be highly aggressive, with seeds widely dispersed by birds and mammals.  Autumn olive can shade out desirable 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, as cut stumps and roots will resprout.

Multiflora Rose

Identification:

  • Multi-stemmed shrub that grows to 15 feet
  • Leaves divided into 5 to 11 sharply-toothed leaflets
  • Stems are green to red and arching, with recurved thorns
  • Clusters of small, 5-petaled, white to pink flowers have a strong fragrance
  • Fruits are small, bright-red rose hips that persist into winter

Habitat:  Once recommended for erosion control and livestock “living fences,” this fast-spreading shrub now inhabits pastures, old fields, roadsides, forests, streambanks and wetlands. Multiflora rose tolerates a broad range of soils and moisture conditions and can thrive in sun or shade.

Native Range: Japan, Korea, Eastern China

U.S. Distribution: Eastern half of the United States as well as Oregon and Washington. 

Local 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.

Japanese Barberry

Identification:

  • Spiny, deciduous shrub usually 1-2 feet, but can grow up to 6 feet in height
  • Small, oval-shaped green leaves with smooth edges turn red in the fall
  • Brown to reddish stems with thorns at each node
  • Small, pale yellow flowers with six petals hang from stems, blooming in spring
  • Fruits are small, bright red, egg-shaped berries that persist into winter
  • Can be confused with the native American barberry, which has toothed leaves

Habitat:  Japanese barberry tolerates a wide range of soils and moisture conditions and can thrive in sun or shade. It is often found in forests, pastures and old fields and along woodland edges, roadsides and disturbed areas.  

Native Range: Japan

U.S. Distribution: Introduced throughout the northeast and Midwest United States, south to Georgia and also in Washington.

Related: Invasive bloody red shrimp discovered in Lake Superior

Local 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. 

For the full list on invasive plants, click here.

Non-Watch List species should be reported using the Midwest Invasive Species Information Network (MISIN) online reporting tool or the MISIN smartphone app. Alternately, these species can be reported to the Cooperative Invasive Species Management Area for your region or your local conservation district.
 

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