Is this nursery plant invasive?

By Maria DeLaundreau, Floodplain Restoration Project Coordinator, Mississippi River Fund

From the description, can you guess what this plant is?

“Ideal ground cover to beautify and control erosion on problem slopes. This hardy perennial ground cover grows 12-24” tall, spreads vigorously to choke weeds, thrives in all soils and all climates…A favorite of state highway crews because of its rapid spreading ability. Blooms June to frost. Drought resistant.”

This plant is being sold even though it is invasive.

If you have volunteered with the Mississippi River Fund and National Park Service pulling invasive species, this description might ring a bell because it is crown vetch. A plant well-known as an invasive that the Department of Transportation and our park have been battling for years. They learned their lesson and stopped planting crown vetch, but it is still sold in the spring 2015 garden catalog I have been scanning. 

Don't plant this invasive tree.

Let’s try another one:

“If you have a large area you’d like screened in a hurry, plant [this tree]…Will grow to a height of 45’ or more, but can be trimmed to form a tall-growing screen. Grows rapidly even in shade and in dry, poor soil, as well as good soils. Does well in drought conditions!”

This plant is Siberian elm, a tree the National Park Service has been striving to eradicate from Coldwater Spring. Pollen and seeds from this tree travel far, allowing it to hybridize with and contaminate the genetics of the native slippery elm even if it is far away. Its ability to grow rapidly even in poor conditions allows it to crowd out native species. 

I was surprised to find these plants in nursery catalogs, but maybe I should have been less surprised. After all, many of the qualities that make a plant invasive are the same qualities that might make it great in a garden and easy for nurseries to market. Don’t you wish every plant you grew was immune to most local diseases, did not have any predators eating it, spread out so you don’t have to buy as many, and grew quickly and lushly even if you forgot to water it or put it in an imperfect location? 

Many of our invasive species did not come to Minnesota by accident; they were brought here on purpose and often because of the qualities that make them invasive. Buckthorn was touted as a fast-growing and dense shrub that quickly screens your yard from neighbors, similarly to how Siberian elm is now being promoted. What was not advertised (and at the time not known) was how buckthorn prevents native flowers from germinating and frog eggs from hatching. At the time, these effects were not known or studied because horticulturalists never expected them to escape yards and gardens, but they did. Once buckthorn escaped it quickly damaged natural areas and has been a challenge for natural resources professionals and volunteers ever since. 

Buckthorn hedges have been planted in the US for over 200 years.
Today you can still find this invasive shrub in yards.

Now you know, if you see a plant that looks too good to be true, it probably is. Check plant descriptions to see if it has characteristics that might make it invasive. You can also check the state noxious and invasive species list  and, supported by the federal Animal and Plant Health Inspection Service (APHIS) and the U.S. Forest Service. Different states and agencies have different plants on their list, so check a couple of references before buying. Still be cautious because not all plants that are invasive have been recognized as such, or may not be invasive in one area and invasive in another. It is safest to stick to natives or plants that have been used in your area and have been tested by time.

There are other ways to keep the park in mind while you are gardening this spring. Support plant suppliers that grow and sell native plants. You can do this by buying and planting native species that provide insect and bird habitat and forage. If you notice plant suppliers selling invasive plants let them know that you do not approve. Conserve water by planting flowers and shrubs that are adapted to Minnesota’s climate, plant a rain garden, or make a rain barrel with Friends of the Mississippi River so when you do water you are still conserving.

Whatever you plant this spring, you will feel better knowing it is helping our park and not harming it. In the comments tell us how you like to be nature-friendly in your garden or warn us of other invasive plants in catalogs and nurseries. As comments come in informing us of other invasive plants on the market, I’ll update the list below.

Invasive plants in catalogs and nurseries:
Siberian elm (Ulmus pumila)
Honeysuckle (Lonicera tatarica)
Crown vetch (Coronilla varia or Securigera varia)
Fire spinner ice plant (Delosperma)
Flame grass (Miscanthus sinensis purpurascens)
Russian olive (Elaeagnus angustifolia)
Baby's breath (Gypsophila paniculata)
Butterfly bush (Buddleja)
Amur maple (Acer ginnala)
Amur silver grass (miscanthus sacchariflorus)
Japanese barberry (Berberis thunbergii)
Tree-of-Heaven (Ailanthus altissima)
Oxeye daisy (Chrysanthemum leucanthemum)
Invasive strains of Phragmites