Planting the Future

AMERICAN WILD YAM

Dioscorea villosa and Dioscorea quaternata

RICHO CECH

As I entered the greenhouse, the humidity and heat enveloped me in a familiar embrace. I bent to push aside the stoneroot plants that surrounded the central bench, and was treated to a deep, lemony fragrance emanating from their yellow flowers. An old calendula plant was inadvertently jiggled and sprayed seeds at my feet. Going down on my knees and peering into the dark, weed-protected recesses under the bench, I found the huge pot of wild yam with its upright vines. Early that spring these vines had tendriled their way up through the slats in the benches, now creating over my bent back a giant plume of heart-shaped leaves and hanging, three-winged fruits.

I was ready to harvest wild yam rhizomes for autumn replanting, but was having a hard time moving the pot. In fact, restricted in this mousehole of a space between the central pole of the greenhouse and a wooden side leg of the bench, I couldn’t gain enough leverage even to budge the pot. Then as my pupils widened in the half-light, I noticed why this pot was so immobile. A large branching rhizome had pushed its way through the drainage hole and solidly anchored itself into the sandy loam and stones of the greenhouse floor. I had to smile at the tenaciousness of this plant, strongly identifying with its urge to find freedom from the confines of a plastic pot. Wielding my trusty snips, I trimmed the vines off above the pot, then with some difficulty snipped the rhizome at the point where it entered the dirt.

Next spring, the new vines would emerge from this remaining piece of rhizome, becoming another permanent feature of this old greenhouse where ginkgo trees, hawthorns, and legions of celandine, larkspur, thistles, grasses, wild lettuce, catnip, clover, buttercups, purslane, plantain, and vervain had already escaped in uncontrolled riot. You get the picture. As someone once said upon entering: “Weedy.” I guess a lot of it comes from my relative respect for weeds and my reticence to demolish good medicine, but the rest of it comes from my own inability to keep up with pulling weeds. They always win.

Turning the wild yam pot on its side, I rolled it out past the stoneroots and over the calendula, noticing as I did so that the alligator-shaped seeds were now being pressed into the eclectic soil mix of the floor, assuring that the yellow and orange flowers would again usher in the spring. I dumped out the pot, revealing a contorted mass of light brown rhizomes, and began to separate and break them into lengths for replanting. The wholesome smell of wild yam, which my friend John once likened to “your mom’s good cooking,” arose in the heat. More potting soil spilled from the tough rootball and covered the calendula seeds with a nice, cushy layer as I continued to wrench away piece after piece of the rhizome. In this fresh state the rhizomes of the wild yam could be broken with effort, but I knew that once they dried, they would be immutable and as hard as bone. The cuttings, carrying their load of fine root hairs and potting soil, were plunked into a bucket and eventually carried into the seed house to weigh. They tipped the scales at more than 5 pounds. That’s what I like about wild yam. Among the forest-dependent species, it increases the fastest. In the wilds I’ve seen big ones at the edge of the woods climb 20 feet into a poplar tree. Working there in the Kentucky shade, poking around after the rhizomes, I found that they covered a prodigious subsurface expanse, gnarling their way among tree roots and through the roots of grasses and other herbs. In its native habitat and under cultivation as well, wild yam is big medicine.

The wild yam root of commerce is actually the entire underground structure of the wild yam, technically a rhizome (thickened, underground stem) and the associated wiry roots. These native American species are herbaceous perennial climbing vines. They are dioecious, having separate male and female plants. The female plants of both species bear distinctive, three-celled fruits that are held curiously upright from the drooping spike by means of a short, hook-shaped stalk. When the fruit dries, it turns from bright green to a papery brown and, upon breaking open, reveals a silvery, mother-of-pearl interior. Each pod contains up to six seeds, which are chocolate brown, flat, and winged for transport by the air.

The plant grows in colonies or clumps at the edge of the forest, where it can find purchase to climb among trees and bushes and where it receives plenty of light. The multiple smooth, green stems bear prominently veined, heartshaped leaves, sometimes occurring in a whorl at the base of the plant, sometimes not. Progressing upward, the leaves attach alternately up the stem, diminishing in size as they reach the tip of the vine. The underside of the leaves may demonstrate a very short pubescence, but apparently this feature has become less prominent since the 1800s. There is regional variation within the species and a possible intergrading of types. The rhizome runs parallel to the ground surface, with wiry roots underneath and short, blunt branches on the sides. The stems strike up from the top of the rhizome. The rhizome grows from the leading tip, and tends to increase its mass by running out, not by becoming thicker.

The plant tends to grow singly in the deep forest or at the edges of the forest. It is not a very inspired climber and tends to be single stemmed; many plants may be found demonstrating only a single whorl of leaves without a vine. Older plants or, perhaps more accurately, plants that receive more nutrients and light will become multiple stemmed and vine up from the forest floor, draping over small brush, young trees, and fallen limbs. The leaves generally occur as two sets of whorls at the base of the plant, followed by an upper vining portion where the leaves occur alternately. The leaves are completely smooth, prominently veined, and heart shaped, and tend to be larger than those of D. villosa, perhaps indicating an adaptation to growing in darker areas. The rhizome is heavy and knuckled like the back of a fist. Wiry roots extend from every portion, and when these break off from the dried rhizome, the nubs can be quite prickly. The rhizome gets heavier by increasing its girth, growing out from the leading tip, and by branching out at the sides. I have seen specimens reach a length of 2 feet and grow as thick as my thumb (pretty thick).

Wild yam prefers moist, humid, mixed deciduous forests. The current distribution of both species encompasses most of the central and eastern states, from Minnesota south to Texas and across to the eastern seaboard, excluding the states of northern New England. However, wild yam can be expected to grow most prolifically in the South.

There is scant evidence of the use of American wild yam among the Native Americans, perhaps because it is too hard to be eaten as food. There is, however, one ethnobotanical reference indicating that the Meskwaki tribe used the root to relieve pain at childbirth. This is consistent with the current use of the root extract as an antispasmodic for smooth muscles and demonstrates again that the Native Americans had a most accurate feel for the uses of the plants that grew around them. In my opinion, the most interesting historical reference to wild yam is found in King’s Dispensatory. The authors mention that from the 1830s (when the Eclectic physicians first began to use the plant) up to the year 1850, the wild yam root of commerce was obtained solely from what they called true wild yam, a plant that was then and is now correctly identified as Dioscorea villosa. Between the years 1850 and 1860, druggists began to notice another type of root mixed into their raw material shipments, which at first they rejected as an adulterant. This new root was much thicker and appeared knuckly, or “knotted.” The diggers, however, insisted that the vines associated with this new root, which came to be called false wild yam were essentially identical, and eventually the druggists were compelled to accept this new root, especially since the true wild yam was becoming “very scarce.” The false wild yam was named Dioscorea villosa var. glabra due to the smoothness of its leaves. This plant is today correctly identified as D. quaternata. However, the rhizomes of these two species of wild yam are still used interchangeably in commerce, and although most of the wild yam employed by herbalists these days is D. quaternata, it is almost without exception labeled as D. villosa. I find it most fascinating that a tradition of adulteration first accepted in 1860 prevails into the year 2000. I find it doubly interesting that issues of overharvest and insufficiency of herbal materials challenged the Eclectic physicians in the mid-1800s just as the increasing scarcity of native medicinal herbs challenges herbalists to this day.

As indicated by its alternate common names—colic root and rheumatism root—wild yam is generally used for allaying pain. Most especially, it has an antispasmodic influence on the gastrointestinal tract and the uterus. It is an old and well-respected treatment for acute abdominal pain, pain caused by gallstones, flatulence, spasmodic hiccups, menstrual cramps, pain and nausea during pregnancy, and rheumatic pain arising from liver and intestinal malfunction. Priest and Priest classify wild yam as a “general relaxant” and recommend the following combinations: wild yam, valerian, and black cohosh for dysmenorrhea and uterine pains; wild yam, cramp bark, and partridgeberry for nervousness, restlessness, and pains of pregnancy.

Wild yam contains a molecule known as diosgenin, which is used for the manufacture of progesterone and steroidal drugs. In fact, birth control pills were first manufactured from components derived from wild yam. However, wild yam does not contain human hormones, but rather the chemical precursors to these hormones. There is an ongoing debate among herbalists as to whether the human body is able to use wild yam, for instance, to assist in manufacture of increased levels of progesterone. There is no known physiological pathway for this synthesis, yet many women find relief from premenstrual syndrome and menopausal symptoms by taking wild yam in the form of a tincture, tea, or “cream.” The creams are most popular. Some commercially manufactured products are made with concentrated extracts of the actual herb, while others contain as their active ingredient synthetically derived progesterone, which is readily absorbed through the skin. I have also noticed that, regardless of whether these creams contain botanical ingredients or not, they are with few exceptions called “Wild Yam Cream.” At Herb Pharm’s analytical laboratory, an unpublished chromatographic study was performed comparing the chemistry of Dioscorea villosa and D. quaternata rhizomes. The purpose of this experiment was to investigate the impact of the industrywide practice of using D. villosa and D. quaternata interchangeably. First of all, the qualitative comparison of the two plants showed a high degree of similarity on the basis of all ten prominent compounds. This immediately put my mind at ease. The best kind of adulterant is one that does not differ in substance from the plant it resembles. In addition, a quantitative analysis was performed, testing the relative concentration of total saponins and diosgenin in the rhizomes of the two plants. The D. villosa contained only 71 percent of the concentration of total saponins found in D. quaternata. Additionally, the D. villosa contained only 77.5 percent as much diosgenin as the D. quaternata. So on the basis of this study at least, it appears that there is no major chemical difference between the two plants, and in fact the plant that the Eclectics named false wild yam may be even stronger than the true wild yam.

Finely sliced and recently dried wild yam rhizome (root) can be made into a decoction or a tincture. To make a strong decoction (basically a simmered tea), put ½ ounce of the dried root pieces or coarsely powdered root in 2 cups of cold water. Bring this slowly to the boiling point, then simmer for ten minutes, remove from the heat, and allow to return to room temperature. Then strain the decoction through a cheesecloth or tea strainer. The dosage is ¼ to ½ cup twice daily or as circumstances require. The tea should not be held over for the next day, but rather made anew.

The tincture is made by combining 1 part by weight (in grams) of finely sliced or ground dried root with 5 parts of liquid (in ml). This liquid, which is known as the menstruum, consists of 50 percent distilled water and 50 percent grain alcohol (190 proof). Using this recipe, 100 grams of the dried root would be combined with 500 ml of menstruum, composed of 250 ml distilled water and 250 ml grain alcohol. The menstruum is added over the dried root in a jar, which is tightly capped and shaken. Then it is stored in a cool and dark place and shaken daily for at least five weeks. The long maceration period is due to the fact that this very hard herb, especially if not thoroughly ground, takes along time to fully extract. After maceration, the herb and liquid are poured off through cheesecloth and thoroughly squeezed into a bowl. The remaining herb, now divested of its medicinal virtues, may be composted. The light yellow liquid is poured back into a jar and allowed to sit overnight; it may then be filtered by pouring slowly through at least four layers of clean cheesecloth, in order to remove any remaining particulate matter. The resulting finished tincture should be stored in an amber glass bottle, in a cool place and out of the light. The dosage is 30 to 60 drops up to five times per day.

The correct dosage of any wild yam preparation is dependent on individual body weight, personal sensitivity, the degree of activity desired, and the urgency of the problem being addressed. Overdose of wild yam can cause nausea, so it is best to start with the lower dosage in order to assure that the herb is well tolerated. In acute conditions, it is not necessary to take any more of this herb than will do the job, but it may be necessary to continue dosage for an extended period of time in order to realize any hormone-regulating effects.

Wild yam grows very well in warm, humid climates. If you live in the North, it makes sense to grow it in the greenhouse. If you live in South Carolina, grow it outdoors.

The seeds tolerate dry storage. They should be sown in the fall, midwinter, or very early spring, outdoors in pots, flats, or directly in a shaded woodland nursery bed. Germination occurs in the spring as the ground warms up. The cold conditioning period, natural rain, snowfall, and oscillating temperatures afforded by sowing the seeds outdoors is a good stimulus to efficient germination. The seedlings are quite sensitive and should be left undisturbed for two years, except (of course) to keep them weeded and watered. Then, once the rootlet begins to swell into a rhizome, the seedling may be transplanted to its final location. The plant prefers open woodlands, partial shade at the edge of the forest, a shaded spot in the garden, or a moist and shady location right in the greenhouse. Because this is a vine, a suitable trellis should be erected, or the plant may be allowed to climb up into bushes and trees. Raising wild yam from seeds takes four years from sowing to harvest of a good-sized root.

It is easy to grow the plant from a piece of the rhizome. Cuttings are usually made in the fall, after the parent plant has matured its fruit and started to die back. Choose the young, vigorous, and growing portions of the rhizome, which are covered with many root hairs, then cut or break the piece to at least 2 inches in length. The cuttings can be planted out immediately, thereby allowing them to become accustomed to the new environment before the growing season. Spring transplanting is possible, but disturbance at this time of year can damage the newly emerging vines. Planted in a good spot in the woods, a nice cutting will grow into a harvestable-sized plant in two or three years.

Planted in shaded beds or pots in the greenhouse, the plants will attain harvestable size in a single season, with significant added yield if the plants are allowed to grow for a full two years.

As with most roots, the best time to dig wild yam is in the fall, after the plant has stored nutrients to carry it through the winter. The roots do not strike very deeply in the soil, but rather crawl around just beneath the surface. The vines are cut back and the rhizome is popped up out of the ground with a spade or trowel and shaken free of clinging dirt or debris. Then the growing tip, attached to at least 4 inches of solid rhizome, is replanted back into the loosened dirt and covered with leaf mulch. This will assure the resurgence of a plant in this spot the following year. The harvested rhizome, with its many wiry rootlets, is thoroughly washed, cut up into small pieces with snips, then dried in the shade on screens. Once dried, these smaller pieces can (with difficulty) be ground to a coarse powder in a coffee grinder or hammer mill. If you forget to snip the fresh root into pieces before drying, you will find that it is impossible to snip it into small pieces after drying. I once watched an apprentice try to break up dried wild yam roots on the front porch using a cold chisel, a brick, and a sledgehammer. He had on a pair of protective goggles and had set up a box to try to catch the pieces, which were ending up almost everywhere but in the box. I picked up several, about the size and hardness of ivory dice, from the middle of the driveway . . . wild yam root is the hardest substance known to the herbalist, and large pieces eat hammer mills alive.

Fresh wild yam root, on the average, has a water content of 64 percent. This means that every 10 pounds of fresh root harvested will dry down to 3.6 pounds of dried root. The rhizome should always be dried before use, because ingesting the fresh root may induce vomiting or other unpleasant symptoms. The roots should be thoroughly dried before storage; incompletely dried root will mold in closed storage. The dried root should be stored in sealed containers, in a cool place and out of the light. According to King’s American Dispensatory, the root prepared in this manner is stable for only a year in storage, after which time any remaining herb should be discarded and replaced by recently harvested and dried material.

UpS RECOMMENDATIONS

• Choose cultivated resources if at all possible.

• Good alternatives include chamomile, licorice, and catnip. Peppermint is a good substitute for digestive issues.

Wild yam lives in a climax hardwood forest and its fate in the wilds rests with the future of this forest ecosystem, upon which it is dependent. As long as the forest is there, wild yam regenerates vigorously by means of clonal division, also spreading to previously uninhabited areas by disseminating its seeds. The rhizome is not subject to rot, and it is hard enough to withstand the onslaught of almost any insect—with the possible exception of highly industrious termites wearing goggles, wielding bricks and cold chisels. Disease does not seem to touch the plant, perhaps due to the presence of saponins, which serve to further protect it from insect predation. How old is wild yam? Counting stem scars on single-stemmed rhizomes of Dioscorea quaternata gives us an approximate age, and in so doing I have found healthy individuals that are at least sixty years old. As long as the forest prevails and we learn to fulfill our herbal needs through cultivation, this wild plant will continue to outlive us all. May it be ever so.

Amarguaye, Ambrose, and Richard A. Cech. “Comparison of American Wild Yam Species.” Williams, Oreg.: Herb Pharm Analytical Laboratory (Ed Smith, director), Nov. 1998.

Felter, Harvey Wickes, M.D., and John Uri Lloyd. King’s American Dispensatory. Vol. 1. 1898. Reprint, Portland, Oreg.: Eclectic Medical Publications, 1983.

Priest, A. W., and L. R. Priest. Herbal Medication. London: L. N. Fowler, 1982.

Smith, Huron H. “Ethnobotany of the Meskwaki Indians.” Bulletin of the Public Museum of Milwaukee 4 (1928): 175-326.