Japanese Knotweed is an invasive perennial, herbaceous shrub that is prohibited in Michigan. It is found in a vast array of soil conditions from roadsides and woodlands to streams and riverbanks. It grows from 5 to 10 feet in height, has an alternate spade or heart shaped leaf arrangement, has flowers that are numerous clusters of small greenish-white petals and it blooms in early August through September. Japanese knotweed is a threat because it grows quickly and creates a dense, unyielding bush that blocks pathways and waterways. It can break through pavement and cement which means it can cause damage to roads and buildings. It is easily spread and can reproduce from a fragment the size of a fingernail. If cutting it or mowing it, dispose of properly by bagging it or burning it, DO NOT COMPOST!
Common buckthorn is an invasive perennial shrub or small tree that is somewhat tolerant of shade. It can be found along roadsides, in old fields and along woodland edges. Common buckthorn can grow from 10 to 25 feet in height and has leaves that are dark green and oval in shape. It has 4 petaled, yellow-green flowers and small round fruit that ripens from green to a purplish black. Common buckthorn is fast growing and forms dense bushes that can suppress native trees and shrubs.
Glossy buckthorn is an invasive perennial shrub that is tolerant of sun and shade, as well as wet and dry soils. It can be found in pastures, along roadsides, in wetlands, and along woodland edges. Glossy buckthorn can grow up to 20 feet in height and has leaves that are dark green and shiny. It has 4 petaled, cream-green flowers and fruit that ripens from red to a purplish black. Glossy buckthorn is fast growing and forms dense bushes that can destroy wildlife habitats and harm forests.
Garlic Mustard is an invasive herb that is found along trails, roadsides and unsettled areas. It grows up to 3 feet in height, has flowers that have 4 small, white petals in a cluster or on a single stem and has triangular, sharply toothed leaves that give off a garlic odor when crushed. Garlic Mustard blooms in late April through early June. Garlic Mustard is a hazard because it excretes an antifungal chemical into the soil which overpowers native trees and plants. Each plant can produce 3,000 seeds which means it can reproduce quickly.
Spotted knapweed is an invasive herbaceous perennial that grows anywhere from 2 to 4 feet in height. Spotted knapweed can be found growing along roadsides, in old fields and pastures, meadows, open forests and disturbed areas. The leaves are pale green to grayish green with rough fine hairs, it has numerous, pink-purple flowers at the end of each stem and has dark tips and fringed margins of its phyllaries (one of the bracts forming the head of a composite plant). Spotted knapweed is listed as a prohibited noxious weed by the Michigan Department of Agriculture due to the fact that it spreads very rapidly and displaces native vegetation.
Phragmites is an invasive plant in the grass family. It is comparable to bamboo and can reach heights of 6 to 13 feet tall. It has leaves that are flat, smooth and lance shaped and range from 8 to 16 inches long. It has flowers (seeds) that look similar to wheat and have long, fringy hairs that are light greenish gray to brownish in color. Phragmites is found in wetlands, ditches, and stream and pond banks. Phragmites provides no food or shelter to native marsh wildlife and destroys the habitats of fish. It menaces beaches by blocking access to swimming areas and decreases property values by obstructing beautiful shoreline views. In the fall, the plant dies, becomes very dry and creates a fire hazard.
Water Hemlock a perennial herbaceous plant from the carrot family. It is one of the deadliest plants in the U.S. due to it being poisonous to humans and animals if ingested. It is found in wet places such as stream banks, ditches, marshes, meadows, and pastures. Water Hemlock grows from 2 to 6 feet in height and has narrow, serrated leaves. It has flowers that are small, white to greenish in color and have 15-30 small crowded clusters that form an almost bractless umbel. Water Hemlock looks similar to Queen Anne’s Lace since they are both members of the carrot family. The easiest way to tell them apart is by their stems. They are both hollow, but the Water Hemlock’s stem has purplish-green striations or grooves and is hairless, and the Queen Anne’s Lace stem is hairy and does NOT have purple striations.
Burnet – Saxifrage
This new invader to be on the watch for is a herbaceous perennial plant belonging to the carrot family called Burnet – Saxifrage. Burnet – Saxifrage can be found in sunny to partly shady areas such as fields and along roadsides. It can grow to be 2-3 feet tall and has umbels or flat clusters of 7 to 20 white or sometimes pink flowers. This plant looks similar to Queen Anne’s Lace.
A new invader to be on the watch for is a herbaceous biennial plant called Cut-Leaf Teasel. Cut-Leaf Teasel likes moist soil and can be found in sunny to partly shady areas such as roadsides, ditches, open fields, and disturbed areas. The flower is a round, cylindrical spike that is 2 to 4 inches tall and consists of hundreds of tiny white to purplish flowers and can grow between 2 to 7 feet in height. Cut-Leaf Teasel has the ability to form large, dense stands that can crowd out native plant species.
In Michigan, the DNR offers volunteer stewardship days when folks can go out with DNR staff and help eliminate invasive plants.
Ottawa Conservation District talks about Hemlock Woolly Adelgid or HWA.