Compass plant’s dramatic height of 6-12 feet and abundance of yellow, sunfliower-like flowers bring radiant cheerfulness to meadows and gardens. A traditional perennial herb of North American prairies, it prefers full sun and moist-to-slightly dry conditions in sandy or loamy soils. Heavy clay will not accommodate the 15-foot-long central tap root. Although it’s a little slow to take off, it will tolerate drought and competition from other plants once established. The thick stem is very sturdy, but it may flop if planted on a slope or in areas buffeted by wind. This amazing plant can live up to 100 years and often occurs in natural habitats alongside big bluestem grass.
Compass plant is similar to cup plant, which is in the same genus. Both are sun-loving, yellow-flowered plants and among the tallest flowers in late summer and autumn. The upper part of compass plant’s light-green stem branches out with clusters of bright yellow flower heads up to 5” across. A mature plant has 6-30 composite flowers that bloom for about 1 ½ months mid-summer.
The two-foot-long basal leaves are reminiscent of pin oak leaves with their deeply cut lobes that vary in shape and give rise to the species name, laciniatum, meaning “slashed: or “torn into divisions.” The genus name, “Silphium” comes from the name of a plant that appeared on ancient Cyrene coins in Greece. Early settlers may have supplied the common name when they noticed the tendency of the large lower leaves to point in a north-south direction to avoid the heat of the sun and use water more efficiently. Because the plant was common on the prairies, early settlers attempted to use it as a compass to guide them in their travels.
Native habitats include black soil or sand prairies, savannas, glades, areas along railroads, and roadsides. Ideal for prairies and meadows, cottage and wildflower gardens, beds, backs of borders, or anywhere a tall and cheerful plant is desired.
Grows 6-12’ tall.
Prefers full sun.
Grows in dry-to-average sandy or loamy soils. Tolerates well-drained, but not heavy clay.
Bright yellow flowerheads are 2-5” across and bloom July-September. Each head consists of 17-35 fertile, yellow ray flowers (petals) surrounding a center disk of sterile, tubular, yellow flowers with brown stamens. Flowers bloom July-September, followed by large, flat seeds that are dispersed by wind and wildlife.
Basal leaves are irregularly divided into long lobes; leaves become progressively smaller as they ascend the stout, sticky stem.
Host plant to 6 species of lepidoptera larvae, including specialists giant eucosma (AKA bird poop moth, pictured here), rosinweed moth, hop borer, and silphius borer. Long-tongued bees such as bumble, miner, and large leaf-cutting are primary pollinators. Other pollinators include halictine bees and syrphid flies. Sulfurs and monarchs visit for nectar. Other specialist feeders of compass plant include prairie cicada, tumbling flower beetle, silphium beetle, and two types of gall wasps. The large seeds are consumed by birds and small mammals.
Medicinal, Edible, and Other Uses:
The hardened sap, or resin, was chewed like gum by Native American children.
Many groups burned the dried root as a charm during lightning storms.
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