Some of the worst problems we have in our restorations are with exotic species – species native to places other than Wisconsin. Organisms – both plants and animals – from other places have been introduced into the U.S. for hundreds of years. The number of exotic invasives has been increasing – mostly because more people and more goods are moving around the globe more often and more easily.
Many exotic species are so common and widespread that we tend to think of them as belonging here. Some species are fairly benign – they don’t seem to cause problems for natives – but others are very disruptive. We have many exotics that we don’t worry about: Cabbage White butterflies, Dandelions (Taraxacum officinale), and Hawksbeard (Crepis tectorum) for example. But other exotics are aggressive and will quickly dominate large areas, reducing the numbers and diversity of native plants.
Here’s my current list of problem exotics. I work hard to eliminate them from as much of the farm as I can. I’ll never be able to completely get rid of any of them, but I’d like to keep them from being problems in our planted prairies, and in our restored prairies and woodlands and wetlands.
European Buckthorn (Rhamnus cathartica)
Reed Canary Grass (Phalaris arundinacea)
Yellow and White Sweet Clover (Melilotus officinalis & M. albus)
Smooth Brome (Bromus inermis)
Common Burdock (Arctium minus)
Common Daisy (Leucanthemum vulgare)
Canada Thistle (Cirsium arvense)
Common St. John’s-wort (Hypericum perforatum)
Orange Hawkweed (Hieracium aurantiacum)
We also have problems with some native plants that have spread because of agricultural practices of the past, or because of changes in land use since settlement. Several native species have invaded areas that used to be prairie, or filled the woodlands with prickly brush.
Here’s a list of natives that we’re trying to control. We’re not interested in eliminating them, just reducing their numbers, and keeping them out of prairie and savanna areas.
White Birch (Betula paperifera)
Trembling and Big-toothed Aspen (Populus tremuloides & P. grandidentata)
Prickly Ash (Zanthoxylum americanum)
Smooth and Staghorn Sumac (Rhus glabra & R. hirta)
Box Elder (Acer negundo)
Canada Goldenrod (Solidago Canadensis)