Tom's Blog

Friday, July 30, 2010

Rudbeckia triloba and Eupatorium sessilifolium

Although black-eyed Susan (Rudbeckia hirta) has been in flower for weeks, another "Susan" has just started. This is Rudbeckia triloba, a nice species that does well in our open savannas as well as the mesic prairies.

In Wisconsin, it is found almost exclusively in the southern part of the state, and Iltis and Cochrane express some doubts about its provenance. However, it is a handsome plant and at Pleasant Valley Conservancy it seems to be "well behaved".

Since it is widespread in Illinois, it is possible that this is a species that is moving north as a result of global warming. According to Illinois data, this is a biennial or short-lived perennial. Since it is a prolific seed producer, we don't have to worry about maintaining it.

It can easily be distinguished from R. hirta by the smaller sizes of its flowers and the three-lobed structure of its lower leaves.

Another species, Eupatorium sessilifolium, is just starting to flower now. This is a State-listed species (Special Concern) that existed only at a single location at Pleasant Valley Conservancy before we began restoration. The original "patch" in Unit 8 had only five plants. Control of buckthorn and sumac helped it spread. Last year we had over 25 plants at the original site and this year Kathie counted 102 plants in that same area. Also, it is spreading to new areas on its own. I have found another patch of three plants at the opposite end of Unit 8, plus a new plant in Unit 19D. In addition, in 2005 we started raising plants in the greenhouse and putting them out in suitable savanna areas. Although seed viability is quite low, the seeds that do germinate produce vigorous plants which transplant well. We now have over a dozen other locations where this species is growing.

It is not too hard to figure out from the photo below where the name "sessilifolium" came from!


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