Silphium laciniatum L.

Compass Plant; Pilot Weed

Herb

Perennial

Vascular

Compass Plant is a native perennial in the Sunflower family (Asteraceae). It is found primarily in the Black Belt region of central Alabama and in other areas underlain by limestone. Compass Plant grows in prairies, on cedar glades, on marl outcrops, and on roadside banks. Compass Plant is a perennial with a large, thick tap root. Plants are scapiform, with the largest leaves forming a basal rosette. The flowering stems are erect, terete, green in color, unbranched, pubescent, and 3-10 feet in height. Leaves are alternate, petiolate (lower leaves) or sessile (upper leaves), lanceolate to ovate in outline, 1–2-pinnately lobed, and pubescent. The margins range from entire to toothed. Flowers are produced in heads. Each head has 27–38 yellow ray flowers, and 100–275 yellow disc flowers. The fruit is an achene. The common name “compass plant” was inspired by the orientation of the basal leaves which are held vertically with the tips pointing north or south. This reduces the amount of solar radiation hitting the leaf surface and helps to reduce the leaf temperature and prevent excess water loss. The resinous sap from the stems has been used as a chewing gum and birds and small mammals eat the seeds. Compass Plant makes an excellent addition to a prairie or wildflower meadow. Because of its deep taproot the easiest way to propagate compass plant is by planting stratified seed in the spring or unstratified seed in the fall.—A. Diamond.

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Native

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