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CAKE's Top 5 Most Unwanted Invasive Plants
Our top 5 most unwanted invasive species were chosen by CISMA staff and the environmental professionals on our steering committee; they are the species we most frequently work on throughout Northern Michigan. The following plants were selected because they're harmful to our local ecosystems, yet not necessarily so widespread that they can't still be managed.
If you have any of these species on your property or suspect that you might contact us for treatment options or a free site visit. In 2022 we are offering free treatments for private property owners and cost-sharing with municipalities.
Black Swallow-Wort
Sometimes called "dog-strangling vine", black and pale swallow-worts are both herbaceous perennial twining vines with clear, watery sap. They commonly reach 1-2 m (3-6.5 ft) in length. They are originally from Europe and in the milkweed family. Black swallow-wort vines thrive in both shade and sun and are often found in disturbed areas along roadsides, pastures, old fields, and gardens.
Cause for concern: Black swallow-wort grows rapidly and can cover other vegetation. Seeds are easily carried by the wind or transported by water. Roots are toxic to mammals, including livestock. Plants are toxic to many insect larvae including monarch caterpillars which may mistake swallow-wort for native milkweed.
dark purple/black 5 petal flowers
a vine that wraps around itself
swallow-wort can be challenging to ID in the spring. Notice the vine twining around itself
dark purple/black 5 petal flowers
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Purple Loosestrife
Purple loosestrife is a perennial herb with a woody, square stem covered in downy hairs. Loosestrife height varies from 4 - 10 ft. In the summer loosestrife has magenta flower spikes with 5-7 petals per flower. Purple loosestrife thrives along roadsides and in wetlands. While seeds can germinate in water, establishment is much more successful in moist soil that’s not flooded. It prefers full sun but can tolerate shade.
Cause for concern: Purple loosestrife can rapidly establish and replace native vegetation. This can lead to a reduction in plant diversity, which reduces habitat value and function for wildlife. Loosestrife can produce over a million seeds annually, and can quickly spread.
Purple Loosestrife is restricted in 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.
Purple Loosestrife has magenta flowers
loosestrife grows in wet areas
purple loosestrife leaves
Purple Loosestrife has magenta flowers
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Phragmites (non-native)
Phragmites is an invasive species with a native counterpart that looks quite similar and can make identification challenging for those unfamiliar with the species. Invasive phragmites range from 6-13 feet in height with green to grayish-green flat leaves. Check out the guide below for more info on how to tell the invasive phragmites from native.
Cause for concern: Phragmites can be difficult to walk through (for humans and wildlife) and often obstructs landowner views because of their ability to grow in tall, dense patches. The exotic strain can reduce native fish and wildlife populations, block out native salt marsh vegetation, and can be a fire danger for nearby residents.
Non-native phragmites are restricted in 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.
young seed head color (Ohio State Weed Lab , The Ohio State University, Bugwood.org)
a perennial grass ranging from 6 - 13 ft
invasive phragmites is often taller than native phragmites and forms dense stands lacking native veg
young seed head color (Ohio State Weed Lab , The Ohio State University, Bugwood.org)
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Japanese Knotweed
We see Japanese, Bohemian, and Giant knotweeds in our region, but Japanese knotweed is most common here. Sometimes called "Michigan Bamboo", invasive knotweeds are an incredibly aggressive plant. Knotweed can be found along roadsides, wetlands, wet depressions, woodland edges, and stream or river banks. This plant can tolerate a wide range of soil, light, and moisture conditions. It is a perennial herbaceous shrub that grows up to 10ft tall with hollow stems and white flowers.
Cause for concern: Japanese knotweed grows very aggressively and has been known to crack building foundations. 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). It is incredibly difficult to get rid of. Please contact us or read the best management practices linked below before attempting to treat this plant yourself.
Japanese Knotweed is prohibited in 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.
knotweed leaves
knotweed growing on lake charlevoix
stalks look like bamboo (Robert Vidéki, Doronicum Kft., Bugwood.org)
knotweed leaves
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Asiatic Bittersweet
Sometimes called Oriental Bittersweet or just invasive bittersweet, this plant also has a native counterpart, American bittersweet. (American Bittersweet is a protected species in Michigan) Look for a woody, perennial vine that can climb up to 60 feet with alternate oblong to round to tapered leaves. Female plants will have berries covered in a yellow outer membrane that opens in the fall.
Cause for concern: Asiatic bittersweet climbs and overtakes native trees and shrubs. Twining vines can girdle trunks and branches, damaging native trees. Dense vines add weight to tree canopies, leading to breakage. Asiatic Bittersweet spreads from roots and seeds that are widely dispersed by birds and wildlife.
red berries with a yellow membrane
see how bittersweet climbs this young tree
bittersweet breaking branches off a large tree
red berries with a yellow membrane
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