Tom's Blog

Sunday, July 6, 2008

Tick trefoil in flower

We have three species of Desmodium at Pleasant Valley Conservancy, illinoiense, canadense, and glutinosum. They are all starting to flower, but glutinosum (pointed tick trefoil) is first and is now in full bloom. This species is widespread in our savannas, and was one of the species we did not have to encourage, as it has spread well on its own.

This is not a really showy plant, but the pastel pink color of the flower is attractive, and even though the flowers are small, they are easy to recognize.

One of the problems with tick trefoil is that its leaves resemble those of poison ivy, and the two species are often found together.

This is a legume, and has the characteristic legume-like flower. It also makes seeds that stick to clothing, and later in the season we will spend some time pulling the seeds off socks and pants.

We have one small stand of tick trefoil that has white instead of pink flowers. I have been following that stand for the past five years and it always comes up with the same color. I assume this is a mutant and would breed true, although I haven't thought this idea important enough to experiment on.

This has been a boom year for tick trefoil, and we have vast patches of it spreading across the savannas. Some of our Carex pennsylvanica patches are completely covered with trefoil plants, which is surprising, as the sedge is clonal and its dense patches usually keep other plants away.

There are several other Desmodium species found in Wisconsin savannas that we don't seem to have. However, some of these are fairly similar to glutinosum and it is possible that we do have them and have just not recognized them. When you have a lot of a single species you tend not to look at it very carefully and may not realize that you are looking at something related. Right now, when all these trefoils are flowering, should be a good time to search for the other species.

The word "trefoil" of course means three-leaved, and there is another plant, bird's foot trefoil (Lotus corniculata), that we also have. The latter, however, is an invasive weed and one we are working hard to eliminate.


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