Tom's Blog

Thursday, July 18, 2013

4 Silphiums

There are four species of Silphium that grow in our area, and right now they are all in flower. Although each has somewhat different requirements, all four are present in some of our prairies. In the photo they are growing side by side.

  • Compass plant: S. laciniatum
  • Prairie dock: S. terebinthenaceum
  • Cup plant: S. perfoliatum
  • Rosin weed: S. integrifolium

Compass plant flowers the earliest. This is the classic prairie plant, found in the logo of The Prairie Enthusiasts. (This organization even has a Compass Club!) Very deep rooted, in favorable conditions it grows very tall. Although its prime habitat is mesic habitats, it is also found in dry, dry-mesic and wet-mesic areas. At Pleasant Valley Conservancy it even blooms on our dry south-facing slope as well as on our open savannas.

Prairie dock only has basal leaves, which are often quite large. Although its habitat is supposed to be wet to wet mesic, we also have it growing in two dry sites, one prairie, the other savanna.

Cup plant is the largest and leafiest, with perfoliate leaves that catch water at the nodes. Its habitat is wet to wet mesic, although we also have it growing on a dry mesic savanna.

Rosin weed is the smallest species, and the latest to bloom. As its Latin species name indicates, its leaves are entire. It is a common member of dry prairies.

Compass plant and prairie dock are known to hybridize. The hybrid grows like prairie dock but has cut leaves like compass plant.

All four species grow well from seed, although it may take a few years before they are well established. However, once established, they should be constant members of the local flora. No prairie should be without them!


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