INVASION OF THE PLANTS
One of the things gardeners do for excitement is to plant something new or exotic to see if it will survive in zone 3. Catalogs, displays in garden centers and friends from other places offer plants that are sure to amaze the neighbors. We bit on one of those in the early 80s only to find out that gorgeous plant was purple loosestrife and I admit there was a little tear in the eye when we grubbed it out and burned it when we realized how invasive it was.
Many of the plants and trees that are becoming a problem in Minnesota were put in with the best of intentions. We call these plants nonnative and those that become a problem are invasives. Some can pose a significant impact on different ecosystems here. There are invasive plants that affect woodlands, farmland, pastures, gardens, urban areas, lakes and waterways. Recognizing and controlling these species is the responsibility of the landowner, gardener, or seasonal resident. Some counties have weed control employees; Beltrami County does not. Learning to recognize and discourage these species is the first step in preserving the quality of our environment. Some of these invasives represent a considerable economic impact as well.
Invasives such as thistle, tansy, hoary alyssum, oxeye daisy, or leafy spurge that invade pasture land can render the forage useless for grazing and even toxic to grazing animals. Woodlands are threatened by invasives such as garlic mustard, exotic honeysuckles, and amur maple. As you drive along roadsides in July, you might notice an extremely aggressive recent invasive by a profusion of lavender flowers - spotted knapweed.
Invasive plant thrive for different reasons. Some have no natural predators to keep them in check; others displace native species with their growth habits. Spotted knapweed is an example of a plant that literally kills its competition - the term is allelopathic. Changing climate is a factor for some. Our warmer winters have helped plants that were killed by colder temperatures to survive. Poison ivy is more numerous now than ten years ago.
There are many species planted and later found to be ecologically harmful. Common buckthorn, Amur maple, and Siberian elm, widely planted as windbreak trees, were later found to displace native shrubs and wetland woody plants. Birdsfoot trefoil, planted as a roadside erosion control ground cover, can now be found far from where it was originally planted, crowding out native grasses.
Unfortunately, many of the invasive species are difficult to eradicate or control. Purple loosestrife produces hundreds of thousands of seeds per plant and also spreads vegetatively so one has to remove every little bit of the root to eliminate it. Some respond to good horticultural practices of mowing and creating a healthy environment for native plants to crowd out the invasive. Chemical control is necessary in some cases but has to be done very carefully to avoid damage to adjacent plants, beneficial insects, wildlife and humans. Professional advice is needed to select the best chemical.
Good information is available to help identify and learn about these invaders. One of the best is the Department of Natural Resources site: www.dnr.state.mn.us/invasives. This resource details the threat of each, control measures and has a good picture. The University of Minnesota Extension site has a list of toxic plants, weeds, and other resources. The US Forest Service (www.fs.fed.us/) has many resources; just search for �invasive species.
Learn to be observant. The invaders have already landed!
