Invasive Species Can Cause A Lot Of Damage Black ripe fruit of the common buckthorn Seeing is believing! Several friends from southern Wisconsin and northern Illinois had described in recent years the unbelievably terrible and damaging effect some invasive plants can have on the native vegetation. Two in particular, the common buckthorn and garlic mustard, are capable of virtually destroying all wildflowers and ferns in some woods by simply overcrowding and shading them out of existence. Charlotte and I attended the Wisconsin Entomological Society annual meeting in Madison recently and, while driving around the northern part of the city, saw with our own eyes the degree to which common buckthorn shrubs can dominate a wooded area. A solid outer wall and understory of 12-15-foot-tall buckthorn shrubs existed in many of the forested areas we passed by. Charlotte Lukes and a solid stand of common buckthorn shrubs This is the ideal time of year to find these plants because their leaves don’t change color before dropping and they also remain on the plants long after other trees and shrubs have lost theirs. Look closely at the green-leaved plants now because several other bad exotics also retain their green leaves for a long time, plants including the Japanese and tartarian honeysuckles and the Russian olive. So many of these undesirable plants, known to spread and crowd out the natives, were initially introduced to our country as ornamentals. Hedgerows and shelter-belts gained popularity during the 1800’s and these plants grew quickly, practically anywhere, and as an added "bonus" produced wildlife cover, nesting sites, and fruit that was attractive to birds and also some mammals. Unfortunately as attractive as the fruits of the buckthorn are to birds, they prove to be very cathartic to the eaters who soon leave their droppings, plus the seeds, all over the countryside. Fence lines and the edges of woods are unusually vulnerable to the growth of dense stands of these horrible exotics simply because it often is these sites where the birds land to seek shelter and to remain out of the way of their predators. Edges of woods are also popular nesting sites. Not only is the common buckthorn known to dominate woodlands, this persistent plant also can quickly invade roadsides, prairies and abandoned fields. Another strength of this plant is its ability to grow in full sun, dense shade and adverse habitats in general. There aren’t many environments where they can’t grow. An effective way of ridding your property of buckthorn is to locate and mark the plants with visible plastic flagging and, come this time of the year, cut the stems or trunks and treat them with an herbicide such as Round-up. Late fall is the ideal time because the sap of the plants is moving downward which, in turn, will take the herbicide directly to the roots, produce maximum absorption and kill the plant. Spring is not the time to chemically treat these plants because the sap at that season is runn ing upward, away from the roots. If you simply cut the twigs or stumps without treating them they will resprout quickly the following year. Naturally one must carefully follow all label instructions for whatever product you choose for treating these and other woody invasives. In case of any questions, your county University Extension agent can provide you with advice. Not all of these fast-growing perennial woody plants produce fruit because they are dioecious, meaning that there are separate male and female plants. Their method of reproduction is primarily by seeds. Some of the birds that are attracted to the fruits are wood ducks, starlings, blackbirds, cedar waxwings, robins and blue jays. Mice are also known to consume the fruits and scatter the seeds. How wonderful it would be if that perfect law could be passed and rigidly enforced making it every landowner’s responsibility to annually remove and control on their entire property the really bad invasive plants including the non-native honeysuckles, garlic mustard, Russian olive and both the common and glossy buckthorns. Violators would receive stiff fines. My guess is that a workable law would be quickly chosen and approved once our county board of supervisors and all town officers would see and experience, firsthand, various environments to the south where such devastation to native plants has occurred due to the take-over by these aggressive exotics. What makes the control of exotics especially challenging is the fact that many plant nurseries continue to sell potentially damaging exotics which, interestingly, many landowners don’t suspect can have dangerous effects on native plant populations. Just a few examples are: Norway maple, Japanese and common barberry, creeping bellflower, oriental bittersweet, Russian and autumn olive, and the Japanese, Amur, Morrow and Tartarian honeysuckle. Vow to improve your stewardship practices by becoming familiar with all plants on your property and, finally, by doing your best to eradicate those terrible invasives that threaten to destroy many of our natives. Now is an excellent time to begin. This column appeared in the Door County Advocate on 11/22/2003. © Copyright 2003 Roy Lukes. All rights reserved.