Any plant of the closely related genera Convolvulus and Calystegia, mostly twining, often weedy, and producing funnel-shaped flowers. Bellbine, or greater bindweed (Calystegia sepium), native in Eurasia and North America, is a twining perennial that grows from creeping, underground stems and is common in hedges and woods and along roadsides. Sea bindweed (C. soldanella) creeps along European seaside sand and gravel. Several Convolvulus species are widespread or conspicuous. The weedy perennial field bindweed (C. arvensis), European but widely naturalized in North America, twines around crop plants and along roadsides. Scammony, a purgative, is derived from the rhizomes of C. scammonia, a trailing perennial native to western Asia. Rosewood oil comes from certain species of Convolvulus.