Tom's Blog

Saturday, July 23, 2011

Purple and white prairie clovers

It has taken us some years but we finally have these two conservative prairie species established at Pleasant Valley Conservancy. Although we had a small population of native Dalea purpurea before we started restoration, it wasn't large enough to serve as a useful seed source. However, there was a tiny remnant along Old Indian Trail (less than a mile away) that had a nice seed source. (Unfortunately, that population is now virtually gone, having been replaced by crown vetch. Grrr!)

We now have nice stands of both species in several of our planted prairies, as well as on the remnant prairie on the south-facing slope in Unit 6.

White prairie clover (Dalea candida) is growing in the same areas as D. purpurea, but in larger patches. This is reasonable, since Cochrane and Iltis state that D. candida is the most widespread of the approx. 160 species of Dalea in the New World.

Both species are sensitive to grazing, reasonable since they are legumes. This probably explains why we originally had D. purpurea only in those parts of our south-facing slope remnant that had been protected from grazing.

The NRCS requires D. purpurea (1-2 ounces per acre) in the seed mix used in Wisconsin when planting a prairie as part of the Conservation Reserve Program (CRP). No explanation given, but I assume it is because of the desirability of having a legume in the mix. (Canada milk vetch, another legume, is also required.)

I suspect that neither of these species will ever "take over" a prairie, whether planted or remnant. At Black Earth Rettenmund Prairie, where both species were present in the original prairie, neither one has ever become dominant, although they are always present in substantial amounts.


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