Avoid Buying Invasive Aquatic Plants

By Emma Costantino,
Outreach Coordinator
North Country Cooperative Invasive Species Management Area

Water gardens are a popular trend in landscaping. While there is a great diversity of aquatic plants to grow in a water garden, many people end up choosing ones that are invasive to Michigan. There is a misconception that if a plant can be bought at a local garden supply store, it must be safe to grow in your backyard. The truth is that several invasive plant species can be bought and sold legally within Michigan. Just because a store is allowed to sell a plant, does not mean it cannot present risks to the local environment. Invasive plants are also commonly sold online. Retailers, including online marketplaces like eBay, may not disclose if a plant is prohibited in certain states, so gardeners can be unaware that the plants they are buying are illegal.

While many popular garden plants are not native to Michigan, only a small percentage of them are considered invasive. Because some invasive plants can still be purchased legally, despite the potential havoc they can cause to Michigan’s waters, it is important for gardeners to learn which plants to avoid. One invasive plant that is still legal to sell is European water clover, which resembles tangled masses of four-leaf clovers. Free-floating plants like water lettuce are also commonly grown in water gardens. This plant, like the name suggests, resembles a small head of lettuce with light green leaves. Water hyacinth is another popular invasive aquatic because of its pretty lavender flowers. The problem with these plants, and other aquatic invasives, is that they do not stay in their own pond.

Many invasive plants are originally grown as ornamentals, but eventually escape cultivation. Aquatic invasive plants that are grown near flowing water, or in areas that flood frequently, can soon spread beyond the garden. Whether growing in a backyard pond or public lake, aquatic invasive plants will form dense colonies in the water. Free-floating plants like water hyacinth can cover a body of water in its purple flowers and crowd out Michigan’s native plants. They block sunlight from entering the water and can reduce the levels of dissolved oxygen. This has a negative impact on the surrounding native plants and wildlife. Dense colonies of invasive plants also impede boat traffic, clog drain pipes, and even block hydroelectric dams.

Because invasive plants reproduce so quickly, plant owners soon find themselves with more plants than they know what to do with. Rather than properly disposing of these unwanted plants, some people will release them into waterways. This leads to the spread of invasive species. Instead, plant owners should place unwanted, aggressively growing plants in a bag before throwing them in the trash; even if the plant is dead. Never compost invasive plants.

There are many native plants gardeners should consider growing instead of buying non-natives. American white waterlily and water smartweed are both good alternatives to the free-floating invasive plants discussed above. There are also many emergent plants, which have roots instead of floating along the surface, that will add diversity to any Michigan water garden, like pickerelweed and blue flag iris. For more information on native alternatives to aquatic invasives, contact NCCISMA. You can also check out the Landscape Alternative app created by the Midwest Invasive Species Plant Network.

Emma Costantino is the North Country Cooperative Invasive Species Management Area (NCCISMA) Outreach Coordinator. She can be reached by calling (313) 570-6853 or by emailing emma.costantino@macd.org.

European Water Clover
Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org


Water Lettuce
Photo Credit: Forest and Kim Starr, Starr Environmental, Bugwood.org


Water Hyacinth
Photo Credit: Wilfredo Robles, Mississippi State University, Bugwood.org


Photo Credit: Chris Evans, University of Illinois, Bugwood.org