3 (5)m, North American Wild Yam is a herbaceous climber with a perennial, brownish rootstock and narrow heartshaped, glossy, fresh green leaves. It is native of humus rich, slightly moist soils in woods and roadsides in the USA. For any humus rich, well drained, slightly rocky soil in full sun to partial shade. Requires a climbing sail. USDA Climate Zone 6. The rhizomes are naturally thin and have at least 1 vegetation point each. VI-VII.