BELWIN CONSERVANCY, A PRIVATE NATURE PRESERVE LOCATED EAST OF MINNEAPOLIS, MINNESOTA, IS DEDICATED TO THE PRESERVATION, RESTORATION AND APPRECIATION OF NATURAL AREAS. Each year more than 10,000 public school students visit the Conservancy to gain an understanding and working knowledge of nature.
The restored prairies and woodlands within Belwin Conservancy also serve as models for ecological restoration in the St. Croix Valley. Non-native invasive plants such as Canada thistle (Cirsium arvense L.) have historically been problematic in prairie restorations. However, a new invader, Grecian foxglove (Digitalis lanata) is impacting desirable plant communities especially on prairie sites.
“We first noticed small populations and began pulling Grecian foxglove on Belwin Conservancy in 2000,” explains Lynette Anderson, Restoration Assistant and Naturalist for the Conservancy. “Starting in 2007, we hired crews each summer to hand-pull and mow the weed, and thought we were holding it in check. Then in 2011, we started finding Grecian foxglove in areas we had never seen it before.”
Today, Grecian foxglove is scattered over all of Conservancy lands with the largest infestation at the organization’s Stagecoach Prairies Natural Area. “Our conundrum is that we don’t know how or why it’s spreading so rapidly in this area—it’s mind boggling,” exclaims Anderson.
Minnesota’s only known infestations of Grecian foxglove are in the St. Croix Valley—some in the heart of Belwin Conservancy. The weed is also on the Minnesota Department of Agriculture’s Eradicate List, increasing the urgency and importance to contain and control infestations.
In 2011, herbicide treatments were integrated into the hand-pulling and mowing program to reduce spread and improve Grecian foxglove control. Lee Shambeau, a commercial applicator working with the Conservancy to manage invasive plants, established field trials to determine the optimum herbicide and rate to control Grecian foxglove.
“There are several different invasive plants growing in association with each other on Belwin, so we wanted a herbicide treatment that would not only control Grecian foxglove, but would also control plants such as Canada thistle and spotted knapweed,” Shambeau explains. “We recommended Opensight® at 3.3 ounces per acre (oz/A) in 2012. Based on results the last two years, we added an additional 0.5 oz/A of metsulfuron methyl to Opensight this year to further improve control on Grecian foxglove. Applying Opensight has given us good control of multiple invasive weed species including the foxglove.”
Grecian foxglove is shallow rooted and relatively easy to pull; however, gloves need to be worn because of the toxic properties of the plant (See Box 3). Volunteers with Belwin Conservancy pull and clip the plant, and crews from Conservation Corp Minnesota crews are hired to hand pull and treat infestations with Opensight® herbicide.
“Our hand pulling program has evolved over the years to reduce the possibility of seed spread,” explains Anderson. “After pulling, plants that are going to seed are hauled from the site to our burn pit, covered with black plastic and burned when conditions allow.”
Field studies are currently being conducted to see if Grecian foxglove plants that are clipped just prior to seed maturation can regrow the following year. There is concern that clipping could encourage perennial growth characteristics in the plant.
Belwin Conservancy provides the bulk of funding for control and containment of invasive plants. The Minnesota Department of Agriculture and the Valley Branch Watershed District provided small grants in 2014. Both funding sources were used to hire the Conservation Corp crews to control Grecian foxglove.
“We hope to work with the Washington Conservation District and the Minnesota Department of Agriculture to see if we can get some additional funding for control in the future,” Anderson explains.
According to the National Park Service which was involved in early control efforts on Grecian foxglove in the St. Croix Valley, the long-term control plan was to allow infested sites to succeed to forest communities and shade out the pest. It didn’t work.
“The threat from Grecian foxglove is similar to other non-native plants with aggressive growth characteristics and high seed production. If natural area managers find Grecian foxglove they need to remove the entire plant as soon as possible and destroy it. This plant spreads so rapidly by seed that you need to have an aggressive program, use herbicides early on in a control effort, and be vigilant for new plants and eradicate them as soon as possible,” concludes Anderson.
For more information, contact Lynette Anderson, Belwin Conservancy: (651) 436-5189.
Belwin Conservancy http://www.belwin.org/news/2011/12/08/grecian-foxglove/
Minnesota Department of Agriculture http://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/foxglove.aspx
Minnesota Wildflowers https://www.minnesotawildflowers.info/flower/grecian-foxglove
National Park Service http://www.nps.gov/sacn/learn/nature/exotic-plants.htm
U.S.D.A. Plants Database http://plants.usda.gov/core/profile?symbol=DILA3
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