Rare native Great Lakes plant to be counted Sept. 20
STURGEON BAY, Wis. -- The public will have an opportunity to help state officials track the status of a very rare native plant that grows in Great Lakes sand dunes during a “thistle count” at Whitefish Dunes State Park on Saturday Sept. 20.
Pitcher’s thistle (Cirsium pitcheri), more commonly known in Door County as the dune thistle, is listed as both a federal and state threatened species. The largest known populations of Pitcher’s thistle in Wisconsin are on Whitefish Bay in Door County, which is also where the 865-acre Whitefish Dunes State Park is located.
“When most people think of thistles, they think of bull or Canada thistle, species that are well known for their prickles and invasive qualities,” says Carolyn Rock, Department of Natural Resources naturalist at the park. “But this is one thistle that deserves our attention and respect.
“Unlike its pest cousins, the dune thistle has a downy surface. Its flowers, which can rise above the sand up to 3 feet, bloom in many different shades from cream to pinkish-tan,” Rock said.
Pitcher’s thistle is found only along the coastal dune environment in the Great Lakes. It grows only in the area between the open sandy beach and fully vegetated dune, which Rock said, is why this rare plant is struggling to survive.
“The Great Lakes dunes habitat is also threatened. More and more homes and condominiums are being built on the dunes, which along with roads to service them, destroy dune thistle habitat. Recreational vehicles operated on dunes, and even people trampling through the dunes can kill off the plants that live there,” she said.
Dune thistles reproducing only by seed, which can be destroyed by high water or blowing sand and eaten by predatory insects.
“Once a seed is lucky enough to find a suitable place to germinate, it sends a taproot deep within the sand,” Rock said. “This taproot may extend down 6 feet or deeper. The first few years, the seedling produces only strap-like leaves. Over the next few years a rosette of leaves form at the sandy surface. After five to eight years, or even up to 12 years, the plant finally sends up a flower stalk.”
Pitcher’s thistle blooms early to mid summer. After blooming, seeds form and ripen then the parent plant dies, completing its life’s mission.
Rock said the key to protecting this rare and unique plant is to protect its habitat. Protection of this type of habitat for this and other species is one reason the park may restrict access to some dunes during different times. The use of herbicides in the area where the dune thistle grows is another threat to the plant, as is the deliberate uprooting of the plant by people who mistake it for other thistles.
Each year, staff and volunteers count the thistles within Whitefish Dunes State Park. Property owners on whose land the thistle grows can join us by keeping track of the plant numbers, locations and protecting the habitat. Other state and federal agencies hold similar counts at other locations around the Great Lakes.
In 2001, there were about 7,800 Pitcher’s thistle plants counted statewide, of which 6,603 were found at Whitefish Dunes State Park. In 2002, more than 9,000 plants were counted at Whitefish Dunes.
People interested in participating in the 2003 count on Saturday, Sept. 20 should register by calling Carolyn Rock at (920) 823-2400. There will be an orientation session for people interested in participating at the park at 9 a.m. and 1 p.m. People may participate in the morning, afternoon, or both times. The Friends of Whitefish Dunes will provide beverages and snacks throughout the day along with lunch.
FOR MORE INFORMATION CONTACT: Carolyn Rock at (920) 823-2400 or Darcy Kind, Landowner Contact Specialist, in the DNR Bureau of Endangered Resources at (608) 267-9789.
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