Yams are warm climate, winter herbaceous, perennial vines. The swollen, starch-rich tuber is their food store, and this is what most people grow them for – they use them as a potato alternative, baked, boiled, mashed or as chips.
Yams need a frost-free, coastal climate and succeed best where there is summer rain and winter drought. They grow well from Sydney north to FN Queensland and around the Top End and south to Perth. While they’ll grow well in coastal WA, they will need plenty of water.
I grow yams because potato is an unreliable crop in Brisbane. I grow two kinds: winged yam, Dioscorea alata, and aerial potato, D. bulbifera. They belong in the Dioscoreaceae family. Yams are highly productive, trouble-free, water efficient and space saving compared to potato (Solanaceae).
In my garden, Winged yam (pictured) can produce a tuber weighing between 15 – 30kg in one growing season. Aerial potato produces tubers in leaf axils on the vine and these are large enough to harvest as well as the tuber in the ground, but they are less productive than winged yam.
Cultivation: To grow them you’ll need compost rich, freely draining soil. I grow my best by planting them in a hole dug two spades deep backfilled with home-made compost. For best returns, water them deeply once a week in dry weather. Give each plant one handful of poultry manure every six weeks during the growing season. I foliar feed mine every fortnight using seaweed.
Winged yam is a vigorous vine, growing to about the spread of a mature passionfruit in one year. In Pacific countries they’re usually planted around the drip line of large trees. Their stems are trained up bamboo canes so they can grow through the canopy unrestricted. Their twining stems readily grow against a fence fitted with wire mesh.
If space is limited, one winged yam can be grown in a space 60cm x 60cm and trained up a sturdy wigwam 3m high. When plants reach the top the cascading growth can be tied in as it descends. They look very attractive trained this way. Just make sure the support is sturdy, as these vines become heavy in summer storms. We filmed harvesting a winged yam grown this way for Gardening Australia.
Aerial potato (Dioscorea bulbifera) reliably produces edible tubers along its stems during late summer to winter. Just like passionfruit, Aerial potato can become weedy in tropical and subtropical gardens, so it’s important that if you grow it you prevent it from growing over your fence or up trees adjoining neighbouring properties. Unharvested, aerial potato stems die during winter, dropping their tubers which then sprout the following spring. Vines can reach 5-10m each season, depending upon care.
I enjoy the sweet fragrance of the summer flowers and their lush growth of aerial potato, but I’ve never seen winged yam bloom. But above all, keep aerial potato vines tamed, trained and harvested, OK? Aerial potato is sometimes available from community gardens and offered at city farms, like Northey Street City Farm in Brisbane. I share my surplus during my Open Days.
The key things are:
1. provide a sturdy support
2. harvest what you grow, and
3. site plants well within your property boundary so none escape
Pests: Yams currently do not have any serious pest or disease problems in Australia. Grasshoppers eat their leaves and leaf-cutter bees (which are beneficial pollinators of legumes) sometimes use leaves for making their egg laying tubes. You may find mealybug on stored tubers. Simply dab these sap sucking pests with methylated spirits.
Harvesting: Yams are winter deciduous, an adaptation to coping with the winter dry season. In autumn their leaves fall, and during winter their stems gradually break up into pieces. Our cue to harvest yams is when their leaves start dropping.
Aerial potato tubers are easily picked off. Save the best for eating and use the smallest for planting.
Winged yam tubers must be dug out carefully because they are fragile. They can grow 50cm or so deep and digging may split them into pieces. After gently cleaning the soil off them, you’ll notice the crown will contain one or more tuberlings (see images).
Winged yams that are starved of water tend also to produce axillary tuberlings. Unlike aerial potatoes, which have smooth skins, the tuberlings of winged yam are covered with grooves. Tuberlings are a survival mechanism, and well watered winged yams don’t produce many: five plants here covered a 30 m long fence and only produced four axillary tuberlings. These are worth gathering for distribution because there are few sources of winged yam.
Harvest time can also be planting time. Yams planted in the cool season won’t need any water until they begin sprouting. In my Brisbane garden this is around October.
Storage: I carefully clean tubers of soil and store them under the house. I have never had to protect them from damage by rats. When I want to cook some winged yam, I just slice off what I need. The cut end will dry, seal and heal without going mouldy – as long as they are stored in a cool, dark, dry, well ventilated space.
Tubers stay fresh until growth resumes in spring. When growth resumes, tubers rapidly become spongy and unpalatable because growth removes moisture and nourishment.
Hunting for planting material: There are hundreds of yam cultivars around the tropical and subtropical regions of the world. The Seed Saver’s Foundation actively encourages local communities to continue growing them. A yam celebration – a community show and tell – which founders Jude & Michel Fanton encouraged in the Solomon Islands resulted in over one hundred yam cultivars being brought together for the first time. The community was surprised at the diversity, and decided to maintain a community conservation collection.
Very few cultivars are grown in Australia. I now have a second winged yam cultivar with purple flesh which I’m eager to trial this year. It was given to me by a keen Brisbane gardener and he reckons it’s as good as the best potato.
You might be lucky enough to find a neighbour, a community garden or a city farm that grows them, but other than that you’ll rarely see them offered. Happy hunting.
Jerry Coleby-Williams
updated 3.7.13
Jerry Coleby-Williams 
i have grown a white flesh purple centered,[ what i think is a sweet potato]. but i cant seem to find out what it is. cant find a photo anywhere. can you help me. the vine is much of a sweet potato vine. ?????
There’s quite a lot of variation in both skin and flesh colour for yams and sweet potatoes. Photos would help identification.
J
Hi Lisa,
The white-skinned sweetpotato is Ipomoea batatas ‘Kestle’.
Cheers
Jerry
Jerry,
I picked up a Yam from Cairns market last year. I’m trying to determine wether this type is an ‘aerial cropper’ or one suited to ‘mounding’ . My trial last year had me securing it to fences which resulted with an amazing vine, yet no tubers. This year I’m planting it in rows and securing the vine along the top of the rows hoping that at the leaf sections, tubers will develop. Your thoughts on this approach would be appreciated and wether the soil should then be prepared as for regular potatoes. Many thanks . Ps live on the Sunshine Coast.
Hi Jeremy,
It’s straightforward.
Aerial potato, Dioscorea bulbifera, produces large, potato-sized tubers in axils. The stems lack flanges.
Winged yam, D. alata, produces a large underground tuber. If it produces axillary tuberlings at all, they will be small. Winged yam gets its specific name in reference to the flanged stems (‘winged’).
If plants don’t produce good sized tubers you need to look at your cultural conditions, both species are easy and reliable.
Jerry
Hi Jeremy.would you please tell me where I can buy this plant (Dioscorea alata) also know as purple yam and UBE in the Philippines ??. I contacted Neil from Limberlost nursery but he could not help.
Best regards:John
John
Try a local community garden or city farm. I sell my surplus to visitors at my open days – next one is May 2013. Details for that via Open Gardens Australia.
Cheers
Jerry
Thank you for sharing your experiences. I really enjoyed this. Blessings!
Jerry, have grown this plant but how do I prepare it to eat.the yams? if they are knocked off the vine while a bit smaller,are they ok to eat?
Easy.
Peel, dice, boil.
Eat the big ones, grow the small one 🙂
Jerry
I’m an ecologist on the Sunshine Coast and I’m starting to find aerial yam in urban bushland near properties where they are being grown. I don’t otherwise find it so it appears to be well outside it’s natural distribution here, and the QLD Herbarium agrees. I have found it forming dense, rapidly spreading infestations, climbing right up and covering trees in bushland and preventing the growth or germination of native species and it appears to be very hard to eradicate. It looks like it might be one of those useful plants you need to be careful of near natural areas.
Hi Melissa
If you follow my work through ABC TV, The Organic Gardener magazine, on Facebook and also this website you will notice I have already covered this topic several times.
Kind regards
Jerry
Hi Jerry, could you please let me know when your next Open Garden day is thanks. Regards, John
Hi John,
Visit the Open Gardens Australia (Qld) website for details in July 2014
Thanks Jerry, I look forward to it. Thanks also for all your gardening info over the years, it really is appreciated. Cheers, John
Hey jerry
Do you know where I could find Dioscorea rotundata or D. cayenensis
I’d like to grow them
Hi Tristen,
Some time ago I bought Dioscorea cayennensis subsp. rotundata from an African food shop in Moorooka. Bit I can’t say if the shop is still there, or if they still sell them. It was a surprise to find them at all! Jerry
I know of a African shop that sells them also, but as far as I know they where not viable as they are sent to quarantine for eradication of pest which kills the yam.
I will keep looking tho
If you happen to come across some live ones let me know
Thanks
Thanks. I love your work.
Very interesting would like to try and grow some can I buy some tubers from you
My Open Day is today. See Open Day blog for details 🙂
Hi Jerry, when is it best to harvest aerial yams? Is there a minimum size, or do I need to wait until the vine dies back for then too?
I have many yams on my vines now, they are between 5cm and 12cm long, but I cannot find any info on when to harvest!
Thank you! 🙂
“Aerial potato (Dioscorea bulbifera) reliably produces edible tubers along its stems during late summer to winter”.
Good day,
I really enjoyed your artical. I believe I have some DIOSCOREA BULBIFERA here in Port Arthur,Texas, USA. My neighbor has grown it all his life and shaired 4 potatoes with me last spring. They grew nicely on a trellis I built. This season I planted 13 on a much wider trellis. All began well enough, but then I decided to feed them. First go around i used a plant food for acidic loving plants. Their growth slowed over 3 weeks. Being unable to live and let live, I called Miracle Gro for advice. Bad idea. The lady didn’t seem to know anything and I could hear her typing, as though she was looking for answers too. She finely told me to raise the PH by adding Lime. Day 5 now and my vines have stopped growing. Do you have a suggestion that may save my plants?
The lesson is they are so easy to grow, just don’t fiddle with pH as they are growing. Feed in the last two months before dormancy as that is the only period when nourishment will contribute to increasing the yield.
Hi, I was wondering if you knew anywhere in Brisbane where I would be able to buy a plant, your post was really interesting and I would love to try and grow some for myself, thank you
Contact community gardens, Northey Street City Farm, or subscribe to my blogs so you know when my next Open Day/ plant sale occurs.