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Flora Fact: Which Way is North?

The leaves of the compass plant can point you in the right direction.

By Jason Singhurst

My first encounter with the compass plant (Silphium laciniatum L.) was in my youth among the chalk limestone prairies of north-central Texas while hiking the trails at the Heard Natural Science Museum near McKinney. The plants looked like little yellow figurines standing in the tall prairie grasses.

As a botanist, I now know why this amazing member of the sunflower family is such a valuable keystone prairie species. The compass plant tends to align its sandpaper-like leaves north to south to avoid the direct rays of the midday sun. This prairie plant navigator has a taproot that may grow to more than 16 feet deep, making it hardy and resistant to drought. Other common names include rosinweed, gum weed, cut-leaf silphium or turpentine plant.

Compass plant is a perennial and a member of the sunflower family. The plant’s flowers are rather large, from 2 to 4 inches in diameter, and are striking on the upper portions of the stems where they occur in clusters. Flowering begins in late June and proceeds through August in Texas.

The compass plant is a typical plant of black soil prairies in the tallgrass region. It often grows with big bluestem (Andropogon gerardii). Other habitats include sand prairies, savannas and glades. The compass plant grows in Central Texas, blackland prairie regions, Northeast Texas prairies and upper coastal prairies of Texas.

Native Americans brewed a root tea from this plant for back or chest pain. The smoke from a burning plant was inhaled to relieve head colds. Indian children chewed the resin.

Small mammals and birds eat the seeds of the compass plant. In grasslands the compass plant provides a sturdy perch for prairie songbirds. Long-tongued bees, including bumblebees, miner bees, large leaf-cutting bees and others, are the primary pollinators of its flowers. The compass plant is grazed by livestock, especially in its juvenile state.

With its imposing height, interesting leaves and abundant yellow flowers, the compass plant is an extraordinary plant. Tallgrass prairies, savannas and glades are complete only with a population of them.

 


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