Plant Portrait - Dioscorea batatas - The Hardy Yam

Most people think of yams as being tropical plants, and therefore unsuitable for cultivation in this country. However, there are a very few species that come from temperate zones and will thrive here. This particular species comes from the mountains of northern Japan and can tolerate temperatures down to about -20°c - it can, therefore, be grown outdoors in most parts of the country.

The plant is a vigorous twining herbaceous climber. It can send out shoots up to 3 metres long each year and these will need supporting. You can grow it like runner beans up a frame or bamboo sticks. It is also possible that this plant will do well on a sunny woodland edge, allowing its shoots to scramble into the branches of shrubs. The main problem here is that harvesting the root is going to cause a lot of disturbance to the other plant roots.

This is a very easily grown plant that succeeds in most fertile well-drained soils. It prefers a position in full sun, though it will also succeed in semi-shade.

The edible root can be up to 1 metre long and weigh 2 kilos or more if it is grown in a good deep soil. It is the shape of a club, about as thick as an adult's finger at its top it thickens to be the size of their arm at its base. The main problem with this plant is harvesting it, you have to dig deep! Once you get it out, the root has a very nice flavour with a floury texture when baked, it is not as tasty as a sweet potato but is better than most yams and superior to potatoes. It makes an excellent staple food and, since yams are now becoming a more common food in Britain, it has a very good potential as a commercial crop here. What is needed is a simple method of harvesting the root.

The tubers can be boiled, baked, fried, mashed, grated and added to soups. They store well and for a long time, and can also be left in the ground and harvested as required in the winter. They contain about 20% starch. 75% water, 0.1% vitamin B1, 10 - 15 mg % vitamin C.

Because yams produce a very vertical root, it is possible to grow a number of plants very close to each other, perhaps at 20 - 30cm spacing. You also get a better overall yield if you leave the plants in the ground for two years. Exceedingly high yields are possible, certainly quite a bit higher than potatoes and with none of the disease problems associated with that plant.

Yam tubers are used medicinally in China and Japan. They are seen as a sweet soothing herb that stimulates the stomach and spleen and has a tonic effect on the lungs and kidneys. The tuber contains allantoin, a cell-proliferant that speeds the healing process. It is used internally in the treatment of poor appetite, chronic diarrhoea, asthma, dry coughs, frequent or uncontrollable urination, diabetes and emotional instability. It is applied externally to ulcers, boils and abscesses. The tubers are harvested in the autumn and can be used raw or baked.

Propagation is a simple matter. Cut off the top 15cm of the root (this is the thin bit, so it is less useful for eating), store it cool and dry for the winter and then replant it in early spring. Do not remove this top portion until you want to eat the yam, though, because it will store much better in one piece.

Yams also form tubercles in late summer and early autumn. These are pea-size swellings in the leaf axils and they fall off the plant when they are ripe. These tubercles are actually baby tubers and are an excellent way of propagating a quantity of the plants. Try and harvest them just before they are ready to fall from the plant and store them in a cool, frost-free place over the winter. Make sure they do not dry out. Pot them up into individual pots in early spring and plant them out when in active growth. They will form tubers about 500 grams in weight their first year, if left in the ground this can increase to 2 kilos or more in their second year.

We have been growing yams for a number of years and thoroughly enjoy eating the roots. The plants have not been entirely happy with us, however, because they do not like our windy site. However, as the tree shelter has increased over the past couple of years we have at last been able to increase our stocks and will be offering this plant in our catalogue in the spring of 1997. Quantities are strictly limited this year, though they should be much more widely available from the autumn. There are many named varieties in China and Japan, though these are not yet available in this country.

Database

The database has more details on these plants: Dioscorea batatas.

Readers Comments

Dioscorea batatas, The Hardy Yam

jenny Tue Feb 24 01:47:02 2004

This plant is the cudzu of my hedge. I didn't plant it. It just apeared one year(about ten years ago), and I spend my summers pulling it up by it's little mini-tubers. It makes the japanese honeysuckle look absolutely benign. I would not recomend planting this in a pot, patch or by your pergolas. If anybody knows how to get rid of it, HELP !!!!

I also have seen clubs who get together in the parks in Florida to pull these vines off of their azaleas and other prize plants because the vine smothers them.

Dioscorea batatas, The Hardy Yam

flick Sun Apr 10 2005

jenny, I think the vine you've got is probably Dioscorea bulbifera aka "air potato", not Dioscorea batatas.

Dioscorea batatas, The Hardy Yam

Jessica Leigh Thu May 5 2005

This site is very effective it helped me with my project I received in Biology class. I would just like to say thank you from a student instead of an overly obsessed gardener.

Dioscorea batatas, The Hardy Yam

rizzir Thu Jun 16 2005

It appears there are three different species of Dioscorea we are talking about here. The one with coconut, softball, or grapefruit-sized bulbils ("tubers") is Dioscorea bulbifera and it can grow up to 80 feet in length and has large leaves. This is the monster eating southern Florida. It appears to crave high humidity and frequent rainfall, so that is why it is not as much of a pest further north or in dry parts of Texas. Dioscorea alata is a much less common variety with squared stems that almost have "wings" off of them. It doesn't flower worth noting or have very large leaves, and so there doesn't seem to be much interest in cultivating it in the U.S. It does get the attractive leaves even though they are smaller, and it does grow quickly and could be a pest if given the chance, as could the others. It also does not appear to be capable of overwintering outside of the deep south in the U.S. Dioscorea oppositifolia, the Chinese yam, also known as Dioscorea batatas, is the one with the cinnamony-smelling flowers. It has smaller leaves, and does not attain the lengths of the others, though one plant can grow a healthy 10 feet or more. The bulbils are not usually bigger than golf balls and most are pea-sized, but every one of them can sprout a vine in areas with high humidity and moisture. The leaves are glossy and handsome, and the vine tough and stringy. It could easily crawl over low native plants and shrubs and kill them due to its ability to thicky shade. The bulbils can stand southern U.S. winters just fine... therefore this vine is considered invasive even in Kentucky. This vine has the propensity to get away from you because the tiny bulbils can fall due to the vine being shaken, brushed, or even blown by wind. It can easily make hundreds of pea-sized bulbils. Add to this that these bulbils taste better than the other varieties and you have a recipe for them being spread by wildlife as well as gravity. That being said, my current infestation of this vine in East Tennessee is no worse than my infestation of chokevine, morning glories, or Japanese honeysuckle, all of which tend to have the same habit. I have found that if I can't get the root up, repeated pulling of the vine at its base eventually exhausts the tuber. Round up is also effective. I feel that growing one or two vines in a pot, and pulling the bulbils off as they form (much like deadheading annuals) would probably contain this vine even in states where it is considered invasive. Each gardener should strongly consider whether s/he has the time to dedicate to doing so before committing to this plant. I can tell you that cleaning up after someone else's infestation was not gratifying ;-) And the vines, left to their own devices, do not flower - it takes true cultivation to achieve it (which explains why it performs better in a pot.)

Gardenweb Do a search for the Latin name, or for "Air Potato"

Dioscorea batatas, The Hardy Yam

mardi love Thu Dec 29 2005

hi everyone. i had a container with D. batatas for the last thirteen years. it was dormant, and while i was away recently, my landlord dumped it. does anyone know where i can find tubers for sale these days? thanks very much, mardi

Dioscorea batatas, The Hardy Yam

O'Neill Sat Apr 22 2006

Me too. Where can I get one? I am in Washington State. oneill@olympus.net

Dioscorea batatas, The Hardy Yam

Becky Mazzarella Tue May 2 2006

These are growing "wild" on the wooded hill behind my house. I have been pulling the little ones up and throwing them in the trash for the last two years and finally have most of them out of my landscaping. I can't believe someone actually wants one! Of course, if you put it in a pot, I guess you will be okay. Becky

ELEMENT STEWARDSHIP ABSTRACT Study done for The Nature Conservancy

Dioscorea batatas, The Hardy Yam

Joe Sat May 13 2006

O'Neill, J.L. Hudson carries packets of the tubercles for propagation.

JL Hudson

Dioscorea batatas, The Hardy Yam

zahrah nasir Wed Nov 29 2006

Hi there. I live in the Lower Himalays in Northern Pakistan at an altitude of 5,800ft. We have very cold winters & warm wet summers with extreme dry in spring & autumn. I introduced Dioscorea batatas to my garden three years ago & have yet to taste one! I starte out with 8 bulbils, purchased from Chiltern seeds U.K. & now have about 30 plants which I am hoping to harvest tomorrow & hoping that the yams are now of an edible size. I did notice a couple of self seeded plants this year but...so far...they are not invasive. The nsails don't bother them which is very important here as potatoes get eaten along with all other root crops. The yams are an attempt at finding something edible, storable & snail proof to later introduce to other subsistence level farmers in these mountains. If you have any alternative suggestions please let me know. Thanks.

Dioscorea batatas, The Hardy Yam

caleb leech Fri Dec 1 2006

The fragrant path also offers it

fragrant path seeds

Dioscorea batatas, The Hardy Yam

Beverly Moody Tue Feb 27 2007

Dioscorea batatas is listed as a Poisonous Plant of N. Carolina here: http://www.ces.ncsu.edu/depts/hort/consumer/poison/Dioscba.htm

Poisonous Plants of North Carolina Dioscorea batatas listed as a Poisonous Plant of N. Carolina

Dioscorea batatas, The Hardy Yam

Ken Fern, Plants for a Future Sun Mar 4 2007

Beverly's post above needs to be taken in context. The report she mentions states that the root is edible cooked, but the foliage and root can cause minor skin irritation when handled raw. In their words 'CAUSES ONLY LOW TOXICITY IF EATEN. SKIN IRRITATION MINOR, OR LASTING ONLY FOR A FEW MINUTES' In my experience, I have never come across anyone who has had a problem handling this plant. In addition, the site also reports a number of other edible plants as having toxic properties. The foliage of carrots is mentioned as possibly causing dermatitis, asparagus, aloe vera, onions and many other well-known edibles are also mentioned here. The site is actually a very good one - it is a fact that many of our edible plants can also have minor, occasionally major, toxins in them. Tomato leaves and green potatoes, for example, have toxins in them. There was a report once in Britain of a person dying after eating a lot of apple seeds. In some cases, such as bitter almonds, the toxins are actually beneficial to the health when consumed in low quantities. It is all a matter of looking at the bigger picture and also of being aware of the facts. The more we know, the less likely we are to make mistakes and harm ourselves when handling or eating plant foods.

Dioscorea batatas, The Hardy Yam

floaty sarah Tue Mar 20 2007

Hello I've read the above postings and am wondering if planting D. batatas will provide me with an income or an invasive pest!! Has anyone in west England or better still West Wales, got any experience? thanks sarah

Dioscorea batatas, The Hardy Yam

Ken Fern, Plants for a Future Tue Mar 20 2007

This plant is quite definitely not an invasive pest in Cornwall. I've grown it for almost 20 years and it has never strayed from where I place it. The plant makes a very large taproot that does not run. You can propagate it by cuttings from the top of this root, though the most productive method of propagation is by means of the pea-sized tubercles that are formed in the leaf axils. Unless you store them, these tubercles will not usually survive the winter outdoors - usually because they are avidly eaten by mice and other creatures. In the polytunnel these tubercles will often overwinter and grow away in the spring, but virtually never has this happened outdoors with me. As regards obtaining an income from the plant - it certainly has the potential, but you need to make sure that you have a market for it. This is not the better known sweet potato and very few British people really know it. I would suggest growing a small crop as a trial and seeing if you can generate a market for it.

Dioscorea batatas, The Hardy Yam

E Siow Sun Dec 16 2007

I have a sort of yam plant, purple inthe stem, leaves look like yam plant. The yam was very hairy & can appear above ground after many years ,can you tell me is the tubles eatable?How do I test it it is not poisonous to man?It do not seem to flower.Is it DISCOREA ALATA? Does Alata has eatable tubules?Please help

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