Roy Lukes: Dune Thistle


There is a native plant now coming into flower that is highly unusual and especially beautiful. If we owned property on which they grow we would guard them jealously, watching over them like a hen chicken looks after her chicks.

Surely some of you will be surprised to learn that this prized and state-threatened plant is a thistle. The fact that they grow on the upper reaches of sandy beaches, where relatively few species can survive, immediately sets this exquisite species apart from those common weedy thistles people throughout the world have come to despise.

The dune or Pitcher’s thistle, discovered by Zina Pitcher (1797-1872), has silvery-gray and tomentose leaves, that is they are densely hairy with matted wool. Its long leaves are deeply cut and barely spiny to the touch, unlike so many of the other thistles, which, like knights in armor, carry their fearsome lances poised for action.

Obviously the light-colored wooly leaves of the dune thistle, Cirsium Pitcheri (SIR-see-um PITCH-er-eye), are wonderfully adapted to conserving moisture and to withstanding the intense sunlight reflected off the predominantly light-colored quartz sand.

Several other plants of this desert-like beach have light, sea green colored foliage, including the rare thick-stem wheat grass, wormwood and false heather with its tiny yellow flowers.

The blossoms of the dune thistle are pale yellow to cream-colored, often beginning with a faint blush of light pink. One thing I failed to do as we admired many of these rare plants was to smell one of the fully opened flowers. All I can do at this moment is wonder if it has a sweet heady fragrance, as does the bull thistle.

It is thought that the treacherous thorny armaments on the bull thistle and others in this small genus offer them protection from browsing animals. One interpretation of the bull thistle’s name is that, like a bull, it too remains “un-cut.” Nothing will touch it!

The thistle genus is surprisingly small in light of the great amount of trouble and anxiety some of the plants cause. Gray’s Manual of Botany lists only 17 species with the addition of several sub-species. Undoubtedly the dune thistle is the rarest and is endemic to the sandy beaches of the Great Lakes. Endemic means that this is the only place in the world where they can be found growing naturally.

A dune thistle flower attracts a bee. Photo by Roy Lukes.

A dune thistle flower attracts a bee. Photo by Roy Lukes.

People possessing sand dune property along portions of Lakes Michigan, Huron and Superior are the sole owners of the Pitcher’s thistles. Ontario, Wisconsin, Michigan, Illinois and Indiana are where they grow sparingly. Keep in mind that all of these lakeshores are not sandy and all of the sandy beaches do not have these rare thistles growing there.

During early July of 1993 friends helped us meticulously count the dune thistles growing along a quarter-mile stretch of the Glidden Drive beach south of Whitefish Dunes State Park in eastern Door County. We confined our counting to an approximately 12-foot wide section near the shore but about five to six feet above the lake level.

We counted 208 plants within this 1,320-foot stretch. They ranged in size from the smallest that was 2½ inches tall and four inches wide to the largest that was 32 inches tall and 24 inches wide. It was common for there to be a couple dozen flower buds on some of the largest of the dune thistles.

Our friends continued the count for another quarter-mile stretch of beach after we left and they added 23 more of the rare thistles. One of them sported 70 blossom buds. What a wonderful find!

Figuring 231 plants to around 2,640 feet of beach turns out to be about one plant to every 11½ feet. Not included in this count was one particularly excellent concentration of several dozen plants growing higher up on the dune. These would be tabulated at another time.

What a fragile and precious environment the beach plant community is. In the first place it has no true soil resulting in very sparse vegetation. Plants here compete very little with each other. Only highly specialized species capable of withstanding harsh conditions can grow and survive.

How exciting it is to be able to stand in one place and see four exceptionally rare plant species – the dune (Pitcher’s) thistle, dune goldenrod, thick-stem wheat grass and sea rocket.

The Whitefish Dunes State Park people know the rare plants well and manage properly for their safety and perpetuation. I would strongly urge the dozens of property owners on whose sandy beaches these rare plants grow to learn about them and other native plants and help in their survival.

The dunes and their rare vegetation are highly fragile and need constant protection. What incredibly wonderful plants grow there. What tender loving care they require!

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