Traditional uses and benefits of Chinese Yam

Chinese yam scientifically known as Dioscorea polystachya or Dioscorea batatas is an ornamental vine belonging to flowering plant in the yam family Dioscoreaceae. The plant is native to East Asia (Japan, Korea, Kuril Islands, Philippines, Vietnam) and was introduced into North America as an ornamental vine. In North America, D. polystachya is currently present in: Alabama, Arkansas, Connecticut, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Vermont, Virginia, and West Virginia. Other names for Chinese yam are Chinese potato, cinnamon vine, cinnamon yam, hardy yam, Japanese mountain yam, Japanese yam, Korean yam, long Chinese yam, wild yam, yam, Japanese mountain vine, Common yam, yam vine and shan yao.

Chinese yam and cinnamon vine are frequently used common names for D. polystachya. Chinese yam refers to its origin from China where the tuber was regularly eaten for starch. The name cinnamon vine is attributed to the cinnamon-like fragrance of D. polystachya flowers. This cinnamon fragrance and showy flowers also contribute to D. polystachya’s attractiveness for horticultural use. The genus name “Dioscorea” is from Dioscoride, in honor of Greek pharmacologist and botanist Pedanius Dioscorides. Polystachya comes from Greek poly & stachys: having many spikes. The edible tubers are cultivated largely in Asia and sometimes used in alternative medicine. This species of yam is unique as the tubers can be eaten raw. People in China eat the roots as a mild tonic food, along with other yams. Japanese people call it nagaimo, which translates to long yam.

Plant Description

Chinese Yam is an invasive climbing or scrambling herbaceous, fast-growing, twining vine that normally grows about 3 to 5 meters tall. The plant is found growing in slopes of hills, edges of rich, mesic bottomland forests, along stream banks and drainage ways, near fencerows, thickets, ravines, creek bottoms, limesinks, granite outcrops, alluvial woods, roadsides, waste places, old home sites, sand prairies, gravel prairies, clay prairies, sandy and rocky savannas, upland savannas, rocky glades, openings and small meadows in upland woodlands and fallow fields. The plant has deep, persistent, root-like tuber up to 1.0 m (3 ft.) long that resprouts annually.  The plant has round slender stems that twine dextrorsely (from left to right, counterclockwise), upwards. The rounded stems are thin and wiry.

Chinese Yam Facts

Leaves

Leaves are usually arranged oppositely, although they may be alternate in the upper nodes, and are occasionally arranged ternately in whorls of 3. Leaves are simple, 7 to 9-nerved (veined), 4 to 8 cm (1.5 to 3 inches) long, and are typically ovate, hastate, or sagittate in shape. Leaves generally have a deeply lobed base, an acuminate tip, and are reddish-purple colored along the leaf margins, petioles, and stems. New leaves often display a distinctive bronze-colored tint.

Flowers

The staminate plants may produce small, yellowish-white flowers annually. The flowers are unisexual (plants dioecious) and arise from the leaf axils in spike or paniculate inflorescences. The perianth is bell-shaped and the staminate (male) flowers are in bundles, spikes or panicles at the end of the branches. The plant may have a spicy fragrance similar to cinnamon. Arrangement may be paniculate or spicate. Flowering normally takes place in between September to October.

Fruit

Fertile flowers are followed by membranous, three angled capsules.  Seeds are winged all around, but the chief means of reproduction are aerial, potato-like tubers (bulbils) located at the leaf axils and underground tubers.

Health benefits of Chinese Yam

Listed below are some of the well-known health benefits of Chinese Yam

1. Controls Blood Sugar

Polysaccharides found abundantly in Chinese yam helps to decrease blood sugar. In the meantime, diosgenin increased insulin sensitivity (by binding to PPAR gamma). Chinese yam may be a good functional food for diabetes or pre-diabetes.

2. Women’s Reproductive Health

Chinese yam may increase progesterone and estrogen levels, according to studies in menopausal rats. In lab settings, it also activated the enzyme aromatase, which makes estrogen. In rodents, it increases the response to the pituitary’s FSH, which along with LH orchestrates the activity of female sex hormones in the body.

In one remarkable case study, a traditional tonic including Chinese yam, rehmannia, epimedium, and other herbs, may have restored fertility in a woman with ovarian failure. However, this was only a single case which has not been repeated in clinical settings. It should not be used as grounds to take Chinese yam for fertility.

3. Skin Health

Mucilage has traditionally been used to soften the skin and manage skin disorders. Mucilage from a variety of plant sources promotes wound healing and soothes rashes and burns. Chinese yam is rich in mucilage; if ground or grated and spread on the skin; it may help heal cuts, scrapes, and other conditions.

4. Digestive Health

According to animal and cell studies, Chinese yam and its extracts may promote the growth of healthy bacteria in the digestive system. Eating Chinese yam increased beneficial Lactobacillus bacteria, blocked the ulcer-causing E. coli, and decreased gut inflammation in mice and rats.

Traditional uses and benefits of Chinese Yam

• Root is traditionally recommended in Chinese herbalism to treat hyperthyroidism, nephritis and diabetes.
• It is used internally in the treatment of tiredness, weight loss, poor appetite, poor digestion, chronic diarrhea, asthma, dry coughs, frequent or uncontrollable urination, diabetes and emotional instability.
• Tubers are harvested in the autumn and can be used raw or baked.
• Leaf juice is used to treat snakebites and scorpion stings.
• Roots are widely used in modern medicine in order to manufacture progesterone and other steroid drugs.
• These are used as contraceptives and in the treatment of various disorders of the genitary organs as well as in a host of other diseases such as asthma and arthritis.
• Chinese yam is used in Chinese herbal medicine, traditionally to treat disorders related to the stomach, spleen, lungs, and kidneys.
• Externally Chinese yam can be applied to ulcers, boils, and abscesses on the skin for treatment.
• It stimulates the stomach and spleen and has an effect on the lungs and kidneys.
• Tuber has been eaten for the treatment of poor appetite, chronic diarrhea, asthma, dry coughs, frequent or uncontrollable urination, diabetes, and emotional instability.
• It is used for treating Intestinal disorders, Gall Bladder Pain and Rheumatoid Arthritis.
• It is used for Postmenstrual Syndrome (PMS) and painful Menstrual periods. It also treats Postmenopausal Vaginal Dryness.
• It is a natural compound that quickens the growth of healthy tissues and reduces healing time.
• It increases energy and sexual desire in both men and women.
• It treats weak bones and Infertility.
• Consuming Chinese yam helps to nourish kidneys and enriching essence as it contains a variety of nutrients which can strengthen the immune system of the body.
• Chinese yam is used to treat weak digestion with fatigue and diarrhea , general weakness, frequent urination, decreased appetite, leucorrhagia (excessive vaginal discharge), premature ejaculation, the symptoms associated with diabetes, and chronic wheezing (whistling sound caused by breathing difficulty) and coughing.
• Rhizome is popular in Chinese herb medicines where it is used to strengthen the lungs, tonify the spleen and kidneys.
• It is useful in treating diarrhea and poor appetite.
• Vitamin A in the tuber performs varied functions like maintaining healthy mucus membranes, night vision, and growth.
• It also provides protection from oral cavity and lung cancers.
• Potassium helps in controlling blood pressure and heart rate.
• Copper present in the tuber helps in production of red blood cells.
• Root extracts help in treating nephritis, hyperthyroidism and diabetes.
• Root extracts are also used internally in the treatment of tiredness, poor indigestion, poor appetite, dry coughs, weight loss, emotional instability and many more.
• Tuber acts as an Anthelmintic element which removes parasites from the gut.

Ayurvedic Health benefits of Chinese Yam

• Stings: Make a paste of the leaves of Yam Rhizome. Apply on the affected area.
• Piles: Cut the cleaned Yam Rhizome in small pieces and dry in sunlight. Now finely powder them and store in a container. Take One tablespoon with water twice a day.
• Obesity: Prepare a juice of Bitter Gourd and Yam Rhizome. Drink it once a day for a week. (Caution: Excessive use may cause toxicity.)
• Night Sweat: Take equal quantity of Rehmannia, Cornus Florida, White Peony, Yam Rhizome, Hoelen, Water Plantain, Anemarrhena and Phellodendron Amurense. Powder all ingredients together. Have one teaspoon with milk at night.
• Energy Tonic : Take dried form of 10 gram Burdock Fruit, 10 gram Chaenomeles Speciosa Fruit, 20 gram Mandarin Orange, 10 gram Acorus Gramineus Rhizome, 10 gram China Root, 20 gram Snow Lotus Root, 10 gram Glehnia Root, 20 gram Yam Rhizome, 10 gram Ginseng Siberian Root, 20 gram Stevia Leaves, 10 gram Licorice and 5 gram Clove Bud. Put all ingredients in a grinder. Make powder. Store in a jar. Boil half a teaspoon in a cup of water. Strain. Have it early in the morning. This tonic increases your stamina and feels you energetic whole day.
• Sexual Health: Morinda Officinalis, Dong Quai, Eucommia, Aconitum Carmichaelii, Goji Berry, Garlic Chives, Ginseng Korean, Cinnamon, Yam Rhizome, Cornus Officinalis, Cnidium, Rehmannia, Cynomorium Songaricum, Cuscuta Chinensis and Horny Goat Weed in conjunction are beneficial for male and female Sexual energy. It increases vitality and stamina. OR You may buy the formula, containing the above mentioned Herbs. Capsule form is readily available. Consume 1 capsule 3 times a day for one month.
• Reproductive Problems of Males: Ginseng Korean, Astragalus, Dong Quai, Rehmannia, Cuscuta Chinensis, Goji Berry, Fennel, Zanthoxylum Piperitum, Morinda Officinalis, Cornus Officinalis, Polyporus Umbellatus, Psoralea, Achyranthes Aspera, Yam Rhizome, Horny Goat Weed, Eucommia, Cinnamon, Paeonia Suffruticosa, Raspberry, Chinese Knotweed, Anemarrhena, Atractylodes Macrocephala, Water Plantain, Senega, White Peony, Anemone Chinensis and Honey, in conjunction are beneficial for Reproductive Problems of Males and act as a powerful kidney tonic. OR You may buy the formula, containing the above mentioned Herbs. Capsule form is readily available. Consume 1 capsule 3 times a day.

Chinese Yam in Combinations

It is common in traditional Chinese medicine to mix herbs to treat specific sets of symptoms. Chinese yam may be combined with the following to treat certain symptoms as shown:

• Chinese yam along with poria and white atractylodes for loose, watery stools.
• Chinese yam together with codonopsis root for general weakness, fatigue, and poor appetite.
• Chinese yam with Chinese foxglove root and cornus for lightheadedness, forgetfulness, insomnia, and related symptoms.
• Chinese yam with ginseng, white atractylodes rhizome, and poria for weakness of the spleen and stomach characterized by poor appetite, lassitude (exhaustion, weakness), and diarrhea.
• Chinese yam with white atractylodes rhizome, poria, and Euryale seed for excessive dampness because of deficiency of the spleen characterized by white leukorrhagia and lassitude.
• Chinese yam with phellodendron bark and plantain seed for excessive dampness changing into heat characterized by yellow vaginal discharge.
• Chinese yam with dogwood fruit and dodder seed for deficient kidneys characterized by lower back pain and leukorrhagia.
• Chinese yam with astragalus root, trichosanthes root, pueraria root, and fresh rehmannia root for the thirst, excessive drinking and eating, lassitude, and frequent urination associated with diabetes.
• Chinese yam with dogwood fruit and prepared rehmannia root for frequent nighttime urination because of deficient kidneys.
• Chinese yam with bitter cardamom and mantis egg case for frequent urination because of deficient kidneys.
• Chinese yam along with glehnia root, schisandra fruit, and ophiopogon root for deficient lungs characterized by chronic cough.

Culinary Uses

• Tuber is consumed after being cooked.
• It has a floury texture with a very pleasant flavor that is rather like a potato.
• Tubers can be boiled, baked, fried, mashed, grated and added to soups.
• This is a top quality root crop, very suitable for use as a staple food.
• Arrowroot can be extracted from the root, though this is not as good at binding other foods as the starch from D. japonica.
• Aerial tubers can be eaten and are very tasty.

Management/Monitoring

Restoration

As with all prolific invaders, the key to the successful control of D. polystachya is to prevent new infestations or to control them as soon as possible. Especially since D. polystachya appears to have a limited range of dispersal, be aware of any new infestations that might arise from nearby planted vines. Dioscorea polystachya has a wide range of environmental adaptability and few pests and predators in North America. It has a high degree of asexual reproductive vigor, and is difficult to manage once firmly established. If controlled during the early stages of invasion, the potential for successful management is high. The potential for large-scale restoration of wild lands where D. polystachya has become established is probably moderate.

Although there is not much conclusive evidence on how best to manage D. polystachya in wild lands, control efforts for this species may be similar to those used for Dioscorea bulbifera (air-potato), another highly invasive non-native plant to North America from the same genus. Currently, the best control of D. polystachya will likely occur with the use of an integrated management approach. The use of manual and mechanical methods followed by another control technique (for example, periodic herbicide sprays to control for new bulbil recruitment and root sprouts) for several years should be accompanied by active restoration efforts to obtain desired results.

Manual and mechanical control

Manual and/or mechanical methods of plant removal can effectively control small isolated patches of D. polystachya. These methods, however, are extremely time and labor-intensive, as the large deep tuber make manual removal very difficult. All pieces of the tuber must carefully be removed or resprouting may occur. Populations will also need to be monitored for several years following plant removal as bulbils in the soil may germinate over several years. There is currently no information on how long these bulbils remain viable.

Peter Whan of TNC’s Edge of Appalachia Preserve System in southern Ohio reports that constant mowing or clipping D. polystachya at the base of the vine (top of the tuber) appears to eventually kill it. How often the shoots must be clipped and for how long of a duration, in order to kill the underground tuber, still remains to be determined. This removal of aboveground biomass appears to eventually exhaust the tuber, and indicates that perhaps a management regime of repeated grazing or burning may also work to kill the plant. These other methods, however, have not been tried.

Manually picking the aerial bulbils off the vines will not kill the plant, but will prevent the further spread of D. polystachya for a growing season. Once the bulbils have dispersed, hand-pulling the young germinating bulbils from soil can be an effective control measure if the entire bulbil is removed.

Chemical control

Herbicide application appears to be the most effective means to control D. polystachya in large infestations. One application of some herbicides can effectively kill all new germinating bulbils, but repeat treatments are probably necessary to completely kill large underground tubers that originally supported large mature vines.

The herbicides glyphosate or triclopyr have been the most successful at killing D. polystachya. Beyerl reports in her greenhouse study, that untreated bulbils had 100% germination, while treated bulbils (using glyphosate) had only 30% germination. Glyphosate also significantly lowered rates of plant growth from germinated bulbils as measured by stem length and numbers of leaves.

Dr. Tom Mueller, a professor at the University of Tennessee, recommends treating D. polystachya with either triclopyr in a 4% solution (4 parts Garlon® + 96 parts water or 3 quarts per acre) or with glyphosate in a 4 to 6% solution. He adds that no additional surfactant is needed with either herbicide for good (95%) control of D. polystachya.

Kristine Johnson, the Supervisory Forester at the Great Smoky Mountains National Park in Tennessee, reports that using triclopyr worked well to control D. polystachya. She adds that the timing of herbicide application is very important, as early season spraying when vines are small and young is not effective, but spraying later in the season on foliage was, apparently because at this time of year significant amounts of the herbicide were translocate to the tuber.

Beyerl however, reports that glyphosate applied to mature vines early in the growing season prevented the production of bulbils. It is unknown if Rodeo would effectively prevent established tubers from resprouting. She adds that applying a herbicide that is not active or persistent in the soil to bulbils during the dormant season can reduce risks to non-target species.

Cliff Chapman, a regional ecologist for Indiana DNR-Division of Nature Preserves uses glyphosate, RoundUp Pro at 5% with 0.5%NuFilm IR surfactant on infestations in low quality areas, and reports moderate success.

Fire

Although there are no conclusive results reported from long-term fire effects on D. polystachya yet, Kristine Johnson of the Great Smoky Mountains National Park has noted that sites burned in a wildfire from the previous fall, had reduced amounts the following year.

Biological control

There are currently no available bio-control agents for D. polystachya. Snails and caterpillars have been observed browsing on leaves of this species, but do not appear to damage the plants significantly. Rodents and other small mammals also consume the bulbils, but the degree of consumption and damage to the plants has not been quantified. The exact species of these consumers have not been determined, nor has it been elucidated if they are specifically feeding on D. polystachya or are only generalist feeders.

Other Facts

• Edible species of Dioscorea have opposite leaves whilst poisonous species have alternate leaves.
• Each vine is capable of producing an average 20 bulbils per year.
• The flowers smell like cinnamon and the twining vine is attractive for arbors, trellises, and along porches.
• The largest tuber may weigh 10 pounds and grow one meter underground.

References:

https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=810115#null
https://pfaf.org/user/plant.aspx?LatinName=Dioscorea+batatas
https://wiki.bugwood.org/Dioscorea_polystachya
https://en.wikipedia.org/wiki/Chinese_yam
https://plants.usda.gov/core/profile?symbol=DIOP
https://www.cabi.org/isc/datasheet/19294
https://gd.eppo.int/taxon/DIUBA
http://www.theplantlist.org/tpl/record/kew-240732

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