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.
- Autumn Olive
Restricted in Michigan
Autumn olive is a deciduos shrub that can grow to 20 feet high. Its leaves are bright green on top and distinctively silver underneath. Spring-blooming cream or yellow flowers have a strong fragrance and abundant red berries are lightly speckled and easily seen in the fall. The flowers bloom in August and September in Michigan.
- Common Buckthorn
Common buckthorn is a shrub or small tree that can grow to 25 feet. It has oval, slightly toothed leaves. Twigs often have a single, sharp thorn at their tips.
- Giant Knotweed
Polygonum sahalinensis (Fallopia sachalinensis)
Giant knotweed is a bamboo-like shrub that can grow up to 12 feet tall. It has white, spike-like flowers and long, heart-shaped leaves.
- Glossy Buckthorn
(Rhamnus frangula or Frangula alnus)
Glossy buckthorn is a shrub or small tree with simple, shiny leaves and pea-sized red to purple fruit. Despite the name, glossy buckthorn has no thorns.
- Japanese Barberry
Japanese barberry is a spiny, deciduous shrub usually 1-2 feet, but can grow up to 6 feet in height. It has small, oval-shaped green leaves with smooth edges. Leaves turn red in the fall.
- Japanese Knotweed
Prohibited in Michigan
Japanese knotweed is a perennial shrub that can grow from 3 - 10 feet high. It has hollow stalks that are persistent through the winter and look similar to bamboo. The stems have a fine white coating that rubs off easily. The flowers are arranged in spikes near the end of the stems that are small, numerous and creamy white in color. Flowers bloom in August and September in Michigan.
- Multiflora Rose
Multiflora rose is a multi-stemmed shrub growing to 15 feet. Flowers are small, white to pink, and have a strong fragrance. Bright-red rose hips develop in the fall and persist into winter.