Herb to Know: Wild Yam

Enlarge Image Image Gallery Wild yam is useful during pregnancy, though it also was used in the first prescription contraception. Photo by Janet Novak

Wild yam (Dioscorea villosa) is a versatile herb that might not win any beauty contests. Its rootstocks grow crooked and bear horizontal branches of long, creeping runners with thin reddish-brown stems that grow to a length of over 30 feet. 

The plant has winged seed pods and clusters of small, drooping yellow-green flowers that bloom from June to August. The heart-shaped leaves are long and broad with furrowed veins, which run lengthwise from the center top of the heart shape and fan outward. The leaves are usually alternate, but sometimes grow in twos and fours near the base of the plant. The upper surface of the leaf is smooth while the underside is downy. 

In medical usage, the herb is best known for chemical components used in the first prescription contraceptive pills. Wild yam root contains diosgenin, which can be converted to synthetic progesterone.

Despite its contraceptive uses, wild yam also is used during pregnancy. Because the herb nourishes the female endocrine system, herbalists believe wild yam can help prevent miscarriage and is one of the best herbs to relieve general pain during pregnancy. Early settlers used the small tubers, as they fell away from the vine, to ease labor pains, colic and leg cramps and to prevent morning sickness and miscarriage.

Wild yam is the basis for many herbal and pharmaceutical remedies and was used widely throughout history in many cultures. The pharmaceutical industry has used yam root as a basis for steroids and cortisone, anti-inflammatory drugs to reduce the swelling caused by rheumatism and hydrocortisone cream to treat eczema. The 16th-century herbalist John Gerard believed it outranked other wild herbs because of its value as a treatment for colic and liver ailments.