Top 13 Invasive Plants in Michigan (Aquatic & Terrestrial) [Updated]
As someone who has or would like to have a pond and/or garden, it’s exceptionally important to understand which plants are native and invasive to your area. Here we are going to focus solely on some of the most notoriously invasive aquatic and terrestrial plants in Michigan.
Making sure that we utilize only native plants here is of critical importance as we work to conserve the integrity of the Great Lakes, its unique plant and animal species, and the world’s largest freshwater supply. Every little bit counts! Your backyard garden can truly be a safe haven for many organisms.
What’s the Big Deal? Aren’t They Just Plants?
Invasive plant introduction to new areas by humans is one of the leading contributors to the loss of native biodiversity, wildlife habitat degradation, and damage to our vital natural resources. For example, a wetland in the American Midwest that has lost much of its native vegetation, such as red-osier dogwood, rushes, monkeyflower, and pickerelweed to invasive species like reed canary grass and phragmites are much less able to filter out pollutants and excess nutrients.
In fact, often within just a few years of being colonized by invasive species, without intervention the wetland or waterway is at great risk of being choked out and disappearing altogether. Not only that, but insects, birds, amphibians, and eventually even mammals move out of the area over time as they lose the cover, food sources, and clean water that were provided by those native plants.
This in turn results in an even greater reduction in ecosystem functioning, and, by extension, the natural resources that we depend on for survival, as only a fraction of the plant and animal species remain. We then lose out on critical ecosystem services, which are functions performed by nature that we depend on, but often take for granted and don’t even think about.
Read on to learn about the top invasive plants in Michigan, and some native alternatives that you can utilize in their place. While there are dozens of invasive plants in this state, we’ll mainly cover the most pervasive and damaging ones. For a complete list of all of Michigan’s invasive plant species, check out the detailed Michigan Natural Features Inventory guide. If you find an invasive species, whether plant or animal, please utilize the Midwest Invasive Species reporting tool to easily report it.
We will also be adding invasive plant lists for other states and countries, so stay tuned! If you’d like a plant guide for your area, don’t hesitate to reach out and let us know! And if there’s a Michigan invasive plant not on this list that you’d like to know more about, comment below!
Top Invasive Aquatic & Marginal Plants in Michigan
Due to its popularity as an oxygenating pond plant commonly sold in aquaculture, Carolina fanwort (often just referred to as fanwort or cabomba) is of particular concern in Michigan’s sensitive waterways. In fact, it’s a restricted plant in Michigan and should be reported using the Midwest Invasive Species reporting tool. Native primarily to South America, its attractive, vibrantly green underwater foliage and ability to oxygenate and filter water have led to its popularity and dispersal worldwide.
Quite a hardy plant, fanwort can be found in permanent (not ephemeral), slow-moving or still waters at least several feet deep with mud or rich substrate where it can dig its roots into. It’s able to survive winters and even water freezing just fine, often retaining its green leaves throughout. This helps the plant to grow and spread quite quickly with little hindrance.
The primary issues with Carolina fanwort are its ability to choke out native plants and block waterways so that it’s more difficult for fish, animals, and watercraft to get through. Within only a couple of years, it forms dense mats that block sunlight to other aquatic plants – even though fanwort is a natural oxygenator, this incongruously results in plant death and decay, which in turn depletes oxygen levels overall and can cause water stagnation.
Curly-leaf pondweed has fairly recently emerged as a problematic invasive species in Michigan, establishing itself in many waterways within the last few years and spreading quickly. As with most of the aquatic species on this list, its establishment outside of its native range of Eurasia is due to its popularity in aquaculture and the ability to easily purchase just about any plant online regardless of location.
With long, wavy, almost crispy-looking (hence the Latin name) leaves, curly-leaf pondweed is able to grow several feet tall and forms dense stands and mats underwater. Like fanwort, a thick root system makes it difficult to get rid of, as it will simply regrow from any broken roots that remain in the ground. It blocks sunlight and the growth of other plants, resulting in massive plant die-offs over the summer and, typically, algal blooms then take over.
This plant is also listed as noxious and restricted in Michigan, so be sure to report it if you find it and certainly don’t purchase or plant it! There are many native Potamogeton species in Michigan, so do try to utilize those if you wish to have pondweed. Curly-leaf pondweed is very easy to distinguish from the native varieties, as it’s the only one with curly leaf edges.
Eurasian watermilfoil hails from, as might be guessed, Eurasia. Its introduction to and widespread establishment in Michigan and, by extension, North America, is due to its featherlike leaves that adeptly filter and oxygenate water, making it a popular aquaculture plant. Another restricted plant in Michigan, it is illegal to own, purchase, sell, distribute, or introduce it anywhere in the state.
However, as with fanwort, these benefits aren’t actually benefits outside of its native range. This is due to its ability to quickly form dense underwater mats that kill off other vegetation and give harmful bacteria and algae species to take hold. Even if you only have or want a small amount of Eurasian watermilfoil, know that it spreads readily and is difficult to remove all root fragments to prevent regrowth.
There is a native variety of watermilfoil in Michigan: northern watermilfoil (Myriophyllum sibiricum). The two can be distinguished by their leaves – northern watermilfoil has leaves with 11 or fewer segments per side of the leaf and a stem that is largely the same width throughout, while Eurasian watermilfoil has leaves with 12 or more segments per side and a stem that is on average twice the width below its flowers as the rest of the stem.
With its small, kidney or heart-shaped leaves that float atop the water’s surface, European frogbit’s introduction into Michigan and many other places outside of its native European range is due to its popularity in aquaculture and ornamental ponds. It’s also known as common frogbit within it native range.
Endangered in its natural habitat yet proliferating at a concerning rate as an invasive species, the benefits and risks of keeping frog-bit varies wildly depending on location. In Michigan, it is a restricted plant, meaning that it’s illegal to own, possess, sell, distribute, or introduce anywhere in the state. It can spread .9 miles within a single growing season, making it one of the most dangerous invasive aquatic plants in the US.
Its floating leaves shade out and kill other plants, again resulting in plant death, lack of oxygen, and algal blooms. Long stems that extend from the bottom of waterways all the way to the surface make travel by fish and other animals quite difficult, and blocks waters so that even boats have a difficult time getting through. It can be found in just about any permanent water source with still or slow-moving water.
Phragmites is our number one most loathed invasive plant on this list. Introduced as a decorative reed, it cannot be denied that mature phragmites looks impressive with its massive average height of 8 to 13 feet and flowing purple, feathery inflorescences at the top of each reed. This is another very illegal plant in Michigan, and considered one of the most dangerous.
Phragmites grows well in just about any damp location, be it along rivers, in the edges of lakes or ponds, or ditches alongside roads. In fact, it’s a common site in the Midwest along expressways, just seas of this tall, thick reed. The root systems are incredibly dense and thick, and so are the stands formed by the reeds. By thick, we mean over 100 shoots per square meter!
Wildlife, fish, and humans alike find it almost impossible to move through, and if you try you will almost certainly get punctured by the incredibly tough stems (trust us – we’ve been there). Even heavy duty trucks find themselves inevitably barricaded by an impenetrable wall when trying to drive through stands to treat and remove them (again, we’ve been there). It’s also a fire hazard once established, and grows so tall that it blocks sunlight and kills everything beneath it and impedes landowner views. Absolutely do not plant phragmites, and absolutely do report it immediately if you find any.
There is a native variety of phragmites in Michigan, Phragmites americanus. It’s only been fairly recently that the two have been recognized as separate species, and as such efforts to eradicate Phragmites australis have negatively impacted native phragmites populations. The native variety has smooth, red or purplish internodes (the area where leaves or a stem connects with another portion of the stem), while invasive phragmites has rough, yellow or tan colored internodes during the growing season.
Another unfortunately very common invasive species in Michigan (and one of the most destructive), purple loosestrife is still often purchased and planted by gardeners and landscapers due to its beautiful, tall purple blooms. Native to Eurasia, some North American nurseries argue that it has value here in its ability to attract pollinators – however, its detriments far outweigh this.
For starters, flowering invasive plants result in pollinators visiting native plants less, which further contributes to the decline of these vital native plants. Pollinators then have significantly fewer pollen and nectar options, as well as fewer host plants for their young, and in turn also decline. It also forms dense stands over time, disrupts nutrient cycling and soil health, and displaces native plants, birds, and insects.
Purple loosestrife can be found in every state in the US except Florida, and is often seen in damp ditches along roadsides, wetlands, near ponds, lakes and rivers, floodplains, and in gardens, fields, and landscaping where they have access to enough water. A native variety of loosestrife in Michigan, winged loosestrife (Lythrum alatum), is being exterminated by purple loosestrife.
Though unlikely to be confused, you can tell the difference between the two easily if you’re unsure: winged loosestrife is significantly smaller at 1 to 4 feet tall, while purple loosestrife averages 6 feet tall. It also has small, solitary flowers located at the bases of its leaves, while purple loosestrife has large clustered spikes of flowers located terminally at the end of each stem. Winged loosestrife is also much more reserved, and will not spread into a large carpet like its invasive kin but rather remains as one or two plants without much spread.
Another of the most prolific invasives on this list, reed canarygrass forms dense green seas within only a season or two of establishment. Unlike the other species on this list, reed canarygrass is actually native to portions of the US. In the Midwest, though, it’s become incredibly invasive as mass agriculture and commercial seed mixtures have accidentally led to its establishment here. Some also plant it to aid in erosion control due to its expansive root systems.
It’s a very hardy grass, drought tolerant and able to sit dormant in soil for years, so it’s been able to take over with gusto. Like most other grasses, its lightweight seeds spread easily on the wind, furthering its distribution, along with its strong, far-spreading rhizomes. If you see acres and acres of reed canary grass, it’s almost guaranteed that they’re all connected to the same rhizomes. It can be found in wetlands, moist grasslands and fields, ditches, and along water edges.
Because the grass family is so very massive (over 10,000 species!), it can be difficult to identify and distinguish species. When it comes to reed canarygrass, though, there’s a surefire way to tell it apart from the native grasses of Michigan. If you gently pull at a leaf and look at where it meets the stem, you will see a thin, transparent sheath or membrane sticking up known as a ligule. Reed canarygrass possesses this transparent ligule, while our native grasses do not.
Don’t underestimate this grass – it’s incredibly difficult to remove. Even repeated doses of professional-grade herbicides and seasonal burning don’t always kill it off. It often takes 5-10 years of repeated treatment to deplete this grass’s seed bank from the soil. This plant is another that’s on the restricted list, and is incredibly illegal to own, spread, sell, etc.
Top Invasive Terrestrial Plants in Michigan
This shrub, with its characteristic silvery leaves, has had a varied history in Michigan. Just a few decades ago, it was viewed as being incredibly valuable to wildlife, as deer and some birds use it for cover and eat the silvery-red berries it produces in the autumn (hence its common name). It was often planted along the edges of farms, powerlines, and dams as a means of helping the wildlife in these otherwise disturbed areas.
However, it began to escape cultivation as early as the late 20th century, particularly within the Great Lakes Basin states of Ohio, Indiana, Illinois, and, of course, Michigan. Each mature plant is able to produce as much as thirty pounds of fruit per year, or 66,000 seeds, meaning that this species has astonishing potential and opportunity for dispersal and further spread. It’s now known as one of the most threatening invasive species in the Midwest.
A native of Asia, autumn olive can grow up to 20 feet tall (though 5 to 10 is more common), and has very sweetly scented, small creamy-white flowers that bloom in early summer. These flowers, and its unique leaves with their silvery sheen and tart berries often used for jams, have made this plant incredibly popular in landscaping. However, once established it is incredibly difficult to get rid of. It easily chokes out native shrubs and trees while forming thick groves, and seeds can persist in the soil for many years.
2. Buckthorn (Rhamnus cathartica/frangula)
Common buckthorn (R. cathartica) and glossy buckthorn (R. frangula) are both prolific invasive species in Michigan, native to Eurasia. They are commonly found in damp woods and along waterways, but can also persist in drier areas like pastures. Similar to autumn olive, buckthorn is commonly planted as an ornamental shrub or small tree, but easily escapes cultivation as birds and other organisms eat the dark purple, almost black, berries and spread them about to different habitats and even across countries as they migrate.
While some argue these shrubs have wildlife value because of this, much of the plant contains an incredibly toxic compound called emodin. Emodin leeched into soil and water from buckthorn directly results in birth defects and death in amphibians like frogs, and death in other animals that consume the berries or leaves.
For small organisms like songbirds and mice, the berries act as a laxative that is so strong it dehydrates them to death. Most animals avoid eating them unless there is nothing else available – which, ironically, is what happens over time where buckthorn is planted as it forms thick copses and chokes out other vegetation.
Furthermore, these thick groves of buckthorn have been found to alter the home ranges and routes of important native megafauna like coyotes, wolves, and deer. Deer and wolves tend to move out of areas with pervasive buckthorn, while coyotes are more likely to be found in urban locations with buckthorn – presumably because they provide cover. Areas thick with invasive species also, as mentioned above, result in many native animals moving out, which means less food for carnivorous animals, too.
It’s important to note that Michigan does have a native buckthorn species, alder-leaved buckthorn (Rhamnus alnifolia). You can easily distinguish it, though, by its shorter stature – alder-leaved buckthorn is typically under 3 feet tall, whereas both invasive varieties grow up to 20 feet tall. In addition, R. alnifolia always has toothed, alternate leaves that are not glossy, whereas both invasive buckthorns have smooth, oval, glossy leaves that can be opposite each other or alternate. Alder-leaved buckthorn has small berries in clusters usually of 3 or fewer, while the other two have larger berries in larger clusters.
We may be a bit biased here, but multiflora rose is among our most-hated invasive species on this list (it’s possible that we’ve fallen prey to its tangled branches covered in thorns a time or two). It is often planted in gardens for its fragrant whitish-pink flowers and ease of growth. However, like the other plants on this list, it overtakes areas fast, and its curving, vine-like branches that can grow up to 16 feet tall adeptly choke out other plants. The presence of countless sharp, strong thorns on each branch make it difficult to remove, and deter most animals from going near it.
Multiflora rose was introduced to North America and Europe in the 1800s from Japan and Korea, where it is native. It was initially used to help prevent erosion and as a sort of “living fence,” but thankfully has since been recognized as terribly invasive, but unfortunately is still widely sold and cultivated by those unaware of how terribly damaging it is. We’re hoping to curb that, at least a bit! It’s very hardy once established, and resistant even to professional-grade herbicides, often requiring several repeated treatments over multiple seasons to fully kill.
Where it has escaped cultivation, multiflora rose can be found readily in just about any opening, be it a woodland path (it’s particularly prevalent along hiking trails), grassland, backyard, or a simple opening in the woods provided by the death of a few trees. It can be easily distinguished from native wild roses, such as the swamp rose (Rosa palustris) by the presence of small, soft hairs (called fringed stipules) at the bases of its leaves and branches. If a rose does not have these hairy stipules, it is very likely a native variety.
A woody vine capable of climbing over 60 feet, oriental bittersweet can be found trailing along the ground toward the beginning of its life and completely encompassing trees later on. As it grows and spreads, oriental bittersweet blocks sunlight from other plants, preventing them from photosynthesizing. They can also girdle, or literally choke, other plants, small shrubs and large trees alike.
Native to Asia, oriental bittersweet was brought here as a charming, trailing ornamental plant. However, we now know just how voraciously this plant spreads – it is now illegal to purchase or transport oriental bittersweet in Michigan. It’s most often found in open woods and along woodland edges, such as trails and the borders of yards, and is mostly easily spotted in autumn when the vegetation from most other plants has dropped off. If you see bright yellow, glossy leaves on vines that readily encompass other plants and structures, it’s very likely oriental bittersweet.
This isn’t the only way that oriental bittersweet is harmful, though. It’s also able to hybridize with Michigan’s native bittersweet species, American bittersweet (Celastrus scandens), resulting in the native variety becoming less and less common. To tell the difference between the two, you must look at the fruits (which ripen in autumn). American bittersweet has yellow fruits that are found terminally on the plant, or at the end of each branch, while oriental bittersweet has red or orange fruits that are found in clusters at the bases of its leaves.
Spotted knapweed is among one of the most common and yet unassuming invasive plants in Michigan. It’s rather small at an average of 2 feet in height, with hairy, almost rough-looking stems, small bluish leaves and bushy purple-pink flowers. It’s often mistaken for thistle due to its flower shape and color. It can at times be mistaken for the native rough blazing star (Liatris aspera), but rough blazing star has purple flowers all along its stem while spotted knapweed has only terminal flowers at the end of each bushy stem.
Spotted knapweed is native to Europe and portions of Asia. It is thought that, since it’s not an overly desirable plant, spotted knapweed was accidentally introduced to North America in the late 1800s via contaminated bags of seeds and soil. These were then spread in pastures and, viola, spotted knapweed took hold as a very hardy, drought tolerant invasive species.
While you’re not incredibly likely to want to plant this in or near your garden or pond, it’s possible that you may have some existing in your yard or nearby, particularly if you have soils that are on the drier side or live near rangeland or a cattle farm. Spotted knapweed is allelopathic and as such is able to kill many nearby plants by exuding toxins into the soil – spotted knapweed often has barren areas around each plant, making it a bit easier to spot.
Another invasive species that is often overlooked, garlic mustard typically grows 1 to 2 feet tall (sometimes taller) and has small white flowers. It starts off small and unassuming, with ground-level leaves that can be round, heart-shaped, or kidney-shaped, often resembling those of wild violets and some buttercups. Despite their relatively small size, a single garlic mustard plant can release 3,000 seeds per season, making it difficult to spot and control until it’s larger (and has already gone to seed).
Native to Eurasia, garlic mustard (sometimes called poor-man’s garlic) was intentionally introduced to the US by settlers as a food source. It’s often still harvested for its strong, characteristic garlic-flavored leaves, which are used to make pesto, dips, and dried spice mixtures. Because it grows early in the spring, it can grow in heavy woods, full shade, and prefers damp soils – meaning you might find it near your pond.
Though it doesn’t possess painful thorns or entangling vines, garlic mustard is another of our most scorned invasives. Its small leaves in the spring make it easy to miss, and bending down to tear them from the ground before they have a chance to flower is no small task in areas where they’ve become rampant. Trying to kill them once they have flowered is an even larger task.
Many people think this plant is just harmless ground cover, but over time garlic mustard is able to kill off its competition by releasing allelopathic compounds into the soil. In areas where garlic mustard is established, there are fewer mature trees due to garlic mustard’s toxins killing off tree seedlings and preventing new generations from maturing.