Three-Toothed Cinquefoil
We found these plants with five-petaled white blossoms and glossy leaves on July 12, 2015, while we were driving along the beaches on the east side of the Keeweenaw Peninsula. They were some of the plants growing in the margin right next to the sandy beach.
The blossoms were extremely white, to the point that they came out completely washed out in the pictures.
The plant has compound leaves, each one composed of three leaflets, similar to what is seen for a lot of other plants ranging from clover and strawberries to poison ivy [1]. The leaflets have smooth edges, and at the tip each one has three “teeth”
This turns out to be Three-Toothed Cinquefoil, Sibbaldiopsis tridentata. It is a cool-climate plant that is found through Eastern Canada and Greenland, and at higher elevations in the Appalachians. And, obviously, along the Lake Superior shoreline in Michigan. It is an evergreen plant, keeping its leaves through the winter. While the leaves are clearly pretty cold-tolerant, I expect that as a low-growing plant it depends on snow cover for insulation [2].
Three-Toothed Cinquefoil is considered endangered in Connecticut, Georgia, Iowa, New Jersey, and Pennsylvania, is a species of special concern in Tennessee, and has gone extinct in Rhode Island, but it certainly seems to be common enough around here.
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[1] The whole “leaflets three, let it be!” warning against poison ivy is only moderately helpful, because (a) there are a lot of other low shrubs and vines that also have compound leaves with triple leaflets, and (b) poison ivy is highly variable in appearance, and looks a lot like many of those other trifoliate plants. Rosie is constantly asking me if every three-leaved plant she sees is poison ivy. It is kind of hard to explain to her what poison ivy actually does look like, because it isn’t really common around here, so I don’t have anything to point to and say “It looks like that!”
[2] Our very deep snow cover (usually a couple of feet at least) is very effective for insulating the ground so that our soil rarely freezes. Which means that, even though this is a cold climate, we can actually have things like potatos and tomatos and squash go feral, in spite of their tubers and seeds not being able to tolerate freezing. Normally, one would have to be considerably south of here, maybe all the way down to Tennessee, before reaching regions where the ground never freezes, allowing those sorts of plants to be able to get through the winter.
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