MADISON - When decorating for the holidays, many people look to nature for raw materials: colorful berries, dried flowers and seed heads can provide for simple but beautiful adornments. But state environmental officials are cautioning that some plants used for wreaths and dried arrangements are actually invasive weeds that can spread if not handled and disposed of carefully.
“When you go looking out your back door in search of inspiration for your next craft or come across a ‘great find’ at a local market, keep in mind that some of these beautiful specimens can cause great environmental damage to our forests, prairies and fields,” says Courtney LeClair, AmeriCorps invasive plant specialist, with the Wisconsin Department of Natural Resources. In particular, people should be on the lookout for bittersweet, multi-flora rose and teasel she says.
Bittersweet is a common vine frequently cut for wreaths and other decorations.
“Many people are unaware that there are two species of bittersweet in Wisconsin,” LeClair says.
The somewhat uncommon native American bittersweet (Celastrus scandens) has large clusters of many fruits at the ends of long stems. A bright orange husk surrounds each deep reddish orange berry. Although it is legal to harvest and use this bittersweet, collectors should always get permission from the landowner first.
The second species Oriental bittersweet (Celastrus orbiculatus) is from Asia and is extremely invasive in Wisconsin.
“The invasive bittersweet can spread by seed into forests, where it winds around trees, climbing to the top where it can topple or strangle the trees,” LeClair says.
This bittersweet can be recognized by its lighter orange fruits surrounded by a pale yellow/orange husk. There are usually just a few berries at each leaf node, rather than the large cluster at the end of the stem.
“Even in the winter, it takes only a minute to look closely to ensure that you are not harvesting and using the invasive species,” she says.
Some people add the deep red fruits or “hips” of rose bushes to their flower arrangements. Although there are many ornamental and native roses that are good to use, the clusters of the invasive multiflora rose (Rosa multiflora) often are used. If wreaths or arrangements are put outside, birds and rodents may feed on the fruits and disperse the seeds of these plants.
Another plant frequently used as a holiday ornament is the spiky oval shaped seed heads from common teasel (Dipsacus fullonum and D. laciniatus). Teasel seed heads are sometimes spray painted to give them even more of a creative splash. If collecting teasels for decorating, make sure all seeds are removed and disposed of in the garbage.
“Often when these flower arrangements or wreaths get old, they are tossed in a compost pile or in the local park or woodlot. If these invasive plants still have seeds, they are probably still viable and can germinate wherever they were disposed of and can start a new infestation,” LeClair says.
Asian bittersweet, multiflora rose and teasel were recently declared as restricted invasive plants throughout Wisconsin. With the new invasive species rule (NR 40, Wis. Admin. Code) that went into effect on September 1, 2009 it is now illegal to transport, introduce, or transfer (buy, sell) these restricted invasive species, unless you are trying to control or dispose of them. Even though you may see some of these species for sale, it is no longer legal to sell them or purchase them in the state of Wisconsin. A full listing of species affected by this rule is available on the DNR Web site.