Prairie Dock - Silphium terbinthinaceum

Culture: Easily grown in average, medium to wet soils in full sun. Prefers moist, rich soils, but tolerates some drought once established. Somewhat slow to establish when grown from seed. Self-seeds in optimum growing conditions.

Noteworthy Characteristics: Silphium perfoliatum, commonly called cup plant, is a coarse, sunflower-like,  native plant which occurs in low woods and thickets, meadows, prairie stream/pond peripheries and along railroad tracks throughout the State. It typically grows on tough, erect stems to 4-8' tall and is distinguished from the other silphiums by its square/quadrangular stems and pairs of cup-forming leaves. Flower heads (to 3" diameter) featuring light yellow rays (20-40) and darker yellow center disks bloom in summer on the upper part of the plant. Rough, triangular to ovate, coarsely-toothed, opposite, connate-perfoliate, medium green leaves. Lower leaves (to 14" long) are united at the petioles. Middle and upper leaves lack petioles, and leaf pairs are united at the bases to envelop the stem forming a cup (hence the common name). Leaf cups will collect rain water. This species is also commonly called cup rosin weed because its stems (like those of all silphiums) exude a gummy sap when broken or cut.) The genus name Silphium comes from the Greek name silphion, used to refer to a North African resin bearing plant.Specific epithet means with leaves surrounding or embracing the stem, which form the "cup" in this species.

Problems: No serious insect or disease problems.

Garden Uses: A large plant that needs lots of space. Some gardeners find cup plant to be too large and weedy for border rears, but others find it to be an effective backdrop for other perennials. Adapts well to prairies, wildflower/native plant gardens, naturalized areas or moist, open woodland areas including stream/pond edges.

All plant information courtesy of the Missouri Botanical Garden