A native of the tallgrass prairie, Cup Plant (Silphium perfoliatum) is an attractive perennial that grows 4 to 10 feet tall. It has large 8-inch-long leaves that are cupped and can hold water (hence its name). In late summer into early fall it produces 3- to 4-inch flowers resembling sunflowers. Cup Plant prefers full sun and loamy soil; it attracts butterflies and goldfinches, the latter of which eat the seeds and drink the water held in the leaves.