Wildflower of the Year
2021 Kansas Wildflower of the Year
Compass Plant (Silphium laciniatum)
Credit: Michael Haddock, kswildflower.org
To see these photos by Michael Haddock and a detailed description of Silphium laciniatum, visit kswildflower.org.
Compass plant is found in roughly the eastern 2/3 of Kansas. It is an erect perennial has stiff, hairy, and sometimes glandular up to two-foot long leaves. The two to five-inch inflorescences are scattered along a flowering stem that can be up to nine-foot tall. Both central disc and outer seed-producing ray flowers help cue that this species is in the Sunflower (Asteraceae) family. Compass plant thrives in both lowland prairies with clay loam to silt loam soils as well as dry, hillside prairie habitat with rocky calcareous soils.
Broken stems exude a gummy resin that can be chewed like gum, and the genus name Silphium comes from the Greek word “silphion”, referring to a North African plant bearing resin. The word “laciniate” means to cut or slash into narrow, irregular lobes which describes the compass plant leaves. The common name refers to the plants tendency to align basal leaves generally north and south, which helps the plant save water by deflecting most of the hot, mid-day summer sunlight.
Once developed over 4-5 years, 15-foot deep compass plant roots make this species extremely drought-tolerant and long-lived. It is an aesthetically-pleasing option for the urban landscape thanks to bright yellow flowers in July to August and stately leaves holding their shape through the winter. If you don’t weed-out new seedlings, however, the tall-statured compass plant can take over a garden.
Compass plant flowers are pollinated primarily by long-tongued bees, but the flowers also attract many other bees and flies and occasionally butterflies. A host of insects eat the plant’s vegetation including a prairie cicada (roots), Silphium beetle (stems and flower heads), gall wasps (stems), and an aphid (sucking juice from the stem). Birds and small mammals eat the large ½-inch seeds. Cattle eat young compass plant leaves and will eradicate this species over time on regularly-grazed pastures.
Seeds show improved germination success with at least two to three months of cold, wet stratification.
Text by Brad Guhr