Prairie-Cup Plant

Cup Plant

Order: Asterales

Family: Asteraceae

Genus: Silphium

Species: S. perfoliatum

General Characteristics: This native perennial plant is about 4-10' tall and remains unbranched, except for the panicle of flowering stems near the apex. The central stem is thick, hairless, and four-sided. The large opposite leaves are up to 8" long and 5" across, which join together around the central stem to form a cup that can hold water, hence the name of the plant. These leaves are broadly lanceolate to cordate, coarsely toothed, and have a rough, sandpapery texture. The yellow composite flowers bloom during early to mid-summer for about 1-1½ months. Each sunflower-like composite flower is about 3-4" across, consisting of numerous yellow disk florets that are surrounded by 18-40 yellow or pale yellow ray florets. The infertile disk florets protrude somewhat from the center and are rather conspicuous, while the ray florets are fertile. The latter produce thin achenes, each with a well-developed marginal wing, which are dispersed to some extent by the wind. The root system consists of a central taproot, and abundant shallow rhizomes that help to spread the plant vegetatively, often forming substantial colonies.

Special Adaptations: Long-tongued bees, butterflies, and skippers are common visitors and the most important pollinators of the flowers. Some short-tongued bees, wasps, bee flies, and other kinds of flies also visit the flowers for pollen or nectar. The larvae of an Antistrophus sp. (Gall Wasp sp.) feed within the stems of this plant, and may attract the hyperparasitic wasp Eurytoma lutea. Various birds, especially goldfinches, are very fond of the seeds, and drink water from the cups formed by the leaves. Because of the tendency to form dense colonies, this plant provides good cover for birds, which often lurk among the leaves during the heat of the day, searching for insects or pausing to rest. Large herbivores, especially cattle, may eat the eat leaves of Cup Plant, especially those of immature plants.