Too much of a good thing? You’ve heard of the poster plants of invasive vegetation: buckthorn, garlic mustard, purple loosestrife, Japanese Asters, and most notable villain-kudzu, to name just a few.
But what about those plants you bring home from the nursery that start taking over your garden. If you purchased a plant, could it possibly be a weed? Unfortunately, yes, and many on the most-wanted list such as loosestrife and garlic mustard originally came from home gardens. According to a study form the University of California Agriculture and Natural Resources, 63% of plants on its invasive plant watch list are ornamental landscape species.
“As long as people want to buy these things, nurseries will sell them,” says Chris Evans, Invasive Species Campaign Coordinator, Illinois Wildlife Action Plan. To the nurseries’ defense, “when they started selling these things, they didn’t know they were invasive.”
For instance, Evans says the Bradford Pear, an ornamental, sterile tree has been around for 20 years and posed no problem till other varieties of ornamental pear trees went on the market recently and started cross- pollinating with it. It’s now reported in every county in the state. “It started exploding and became an invader.”
By some estimates, the U.S. spends as much as $137 billion annually fighting the impact and trying to control 800 invasive species. Botanic gardens, nature conservancies and even some garden centers around the country have made steady progress educating consumers about invasive plants. For instance, the Chicago Botanic Garden maintains the Best Plants website to help gardeners select non-invasive plants in Illinois. Meijer, which has nearly 200 retail stores in the Midwest, partnered with the Nature Conservancy to help customers identify non-invasive plants.
And while most non-natives are safe, if you see the catch phrase “naturalizes” or “spreads easily,” be on alert. Here a few plants that are either invasive or have a propensity for overzealous growth:
- American Grape Hyacinth (Muscari armeniacum): About ten years ago, my husband was so excited to find a bulb the rabbits wouldn’t devour that he lined our entire front and back gardens with them. While the cobalt blue blossoms are beautiful in bloom, they have started to take over, and their green foliage dies back only briefly before coming back again in the fall, choking out other plants. Among the bad boys of invasive plants these are a minor player.
- Campanula rapunculoides: Also known as Creeping Bellflower or Rampion Bellflower, this plant has 5-petal, delicate lavender flowers, and was introduced from Eurasia as an ornamental. Its rhizomes send out lateral roots, making it difficult to control. It now lines the highways of states such as Wisconsin and New York. It requires digging out the plant and taproots. Last summer I spent several back-breaking weeks digging this out of my mother’s garden, untangled its roots from irises and many other perennials.
- Baby’s Breath (Gypsophila paniculata) This innocuously named plant with its delicate flowers escaped from home gardens and has now spread throughout the U.S., and invaded the Lake Michigan lakefront. The Sleeping Bear Dunes, a National Lakeshore Park in Michigan, reports that the plant’s billowy tiny flowers belie its vigorous taproot, which can grow to over 6 feet. Not only does the plant strangle the native dune grasses, it “over-stabilizes” the dunes, stopping the natural movement of the sand.
- Common, or orange daylily, also referred to as Tiger Lilies, came to the U.S. from Asia in the late 1800s as an ornamental. They’ve managed to escape gardens into fields, meadows, flood plains and the edges of forests. If you’ve ever tried to remove a clump of daylilies, you’ll know how difficult it is to extract the thick band of tubers.
If you’re unsure about a plant, the USDA keeps a comprehensive website directory of invasive plants.
You can always call your local botanic garden or cooperative extensive for more information. And then take action, either physically eradicating the invasive plant or using a recommended herbicide.
Do you have a plant that is taking over your garden? Let us know about it!