Tom's Blog

Sunday, June 15, 2008

The compass plant: a prairie icon

The compass plant, Silphium laciniatum, is one of the signature species of a tall grass prairie. It is featured in the logo of The Prairie Enthusiasts, emphasizing its iconic nature. Its modal habitat is the mesic prairie, although it is also found on wet- and dry-mesic sites. It is only absent on really dry sites, such as steep south-facing hillsides ("goat" prairies).

Compass plants are very deep-rooted species and generally take five or six years to become well enough established to flower. Their first few years in a new prairie planting are occupied with sending down deep roots. In the first or second growing season only one or two leaves are visible. However, the leaves are very characteristic and even a single leaf is easy to recognize in a new planting (see photo).

Compass plants are very sensitive to grazing and they are one of the first plants to disappear when a prairie pasture is opened to cattle.

We have been planting compass plants at Pleasant Valley Conservancy since we first began restoration. Planted prairies such as Toby's Prairie and (especially) the Pocket Prairie have now well-established populations. In addition, we have included compass plant seeds in the dry-mesic mix we have been using in the more open areas of our savannas.

Just this year, for the first time, I have started to see compass plants in the open area of one of our bur oak savannas (see photo). It is possible that these plants have been here for a few years but were hidden under the tall vegetation that thrives in these savannas. So far I have seen two plants in this savanna, although a careful search might uncover more. It may take a few years yet before they will flower.


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