Silphium perfoliatum

Cup plant is a giant of the summer prairie, a statuesque perennial that rises on stout, square stems to eight feet or more and lifts a crown of bright yellow, daisy-like flowers above the border. The name comes from a quirk of the foliage: the large, coarse leaves are perfoliate, joined in pairs around the stem to form a shallow cup that catches and holds rainwater. Silphium perfoliatum belongs to the sunflower tribe of the aster family, Asteraceae, and shares that clan's generosity of bloom.

Those little cups are the plant's charm and its theatre. Rainwater pools in each leaf axil, so that a bent stem pours a small waterfall, an old amusement for children, and, more usefully, a drinking fountain for American goldfinches and other small birds that perch to sip. The flowers feed a wide traffic of bees and butterflies through mid and late summer, and the ripe seed draws finches back to the plant well into fall. The Woodlanders stock is originally from Missouri.

Cup plant carries a deep record of human use as well. Native peoples across eastern and central North America turned to the root as a tonic and a diuretic, the Chippewa treating lung ailments, hemorrhage, and joint pain, and the Ojibwe taking root infusions for rheumatic back pain and stomach trouble; the young spring leaves were cooked as a green, and the fragrant resin was chewed like gum. A prairie plant by nature, cup plant grows along streams, in low meadows, and on the sunny edges of woodland, thriving where the ground stays moist.

In the garden, use cup plant at the back of a large border, in a rain garden or damp meadow, or as a bold screen where the towering stems and yellow bloom can preside over lower planting. The species self-sows and spreads by a stout root, so give room and site where a colony is welcome; small seedlings transplant easily, though established plants resist moving. Pair with Joe-Pye weed, ironweed, and switchgrass in full sun to part shade, and let the finches find the cups.