Nutritious knobbly tuber is surprise best-seller

oca tuber

An odd-looking tuber vegetable is proving to be a surprise best-seller for mail order horticultural firm, Thompson & Morgan.

ocaOca is a knobbly root vegetable that looks a bit like an artichoke. Don’t worry though; they don’t have the same windy after effect! The tubers have a tangy lemon taste which becomes deliciously nuttier when cooked. The red-skinned variety available from T&M have a crisp pale orange or creamy-coloured flesh – fans of ‘eating raw’ can simply wash and slice their oca tubers into salads or crunch them as a tasty and wholesome snack. Oca becomes more starchy when cooked and can be enjoyed similarly to potatoes – boiled, baked, mashed and fried – whilst the shoots and the attractive shamrock-shaped leaves can be added to salads for a tasty citrusy tang.

‘We think that people are buying oca in response to more information being available about it’, commented Paul Hansord, T&M’s commercial director. ‘Oca is easy-to-grow and nutritious and, thanks to some good press recently, it seems to be increasingly appealing to health-conscious gardeners and foodies alike’.

Oca – aka New Zealand yam (it is grown commercially in New Zealand, hence its alternative moniker) – is cultivated extensively in the Andes where it is second only to the potato in terms of the most widely-grown root vegetable. T&M’s trials showed that the perennial oca plant performed well in the UK climate and did not suffer from blight or any noticeable pests. Oca is known to tolerate poor soils and different climatic conditions, which makes it ideal for any British kitchen garden. Plants are attractive too, so gardeners can also cultivate their oca in containers on the patio or decking area.

new zealand yamThe nutritional and health-promoting benefits of oca make it well worth growing. It boasts a wide range of micro and macro nutrients including Vitamin C, iron, zinc, calcium, flavonoids, B vitamins and fibre. It is an excellent source of carbohydrates and phosphorus, as well as essential amino acids that promote the health and proper function of muscles, organs, nails, hair, skin and more. Oca is also notably low in calories.

Oca or New Zealand yam is available from Thompson & Morgan’s website . Due to the popularity of this nutritious, knobbly tuber and as T&M is only despatching oca until the end of March, customers are being offered 5 tubers for £4.50 and 10 tubers for £6.50 – half their original price. Gardeners will find full growing details for oca on the T&M website

Recipe idea
Rosemary roasted oca: Preheat oven to 200°C/Gas 6. Wash and then cut any larger oca into chunks so that they’re all roughly the same size. Toss in just enough olive or sunflower oil to coat and then sprinkle with fresh rosemary leaves. Season with salt and pepper. Roast for about 15 minutes for very small ones, 20-25 minutes or so for larger oca. They’re ready when they feel tender when pierced with a knife.

Sonia Mermagen

Sonia works at Thompson & Morgan in the role of press and communications officer. She is a self-proclaimed ‘reluctant’ gardener and is generally amazed if anything flourishes in her garden. Sonia has a ‘hands off’ approach to gardening and believes that this helps to encourage bees, butterflies and other wildlife. (That’s her excuse anyway!)

Oca – the taste test

Oca – the taste test

In January one of our guest bloggers wrote about oca, a vegetable originally from South America that’s grown very much like potatoes. The knobbly tubers need a relatively long growing season before being harvested in the autumn, about 2 weeks after frost has killed the top growth. Exposing the harvested tubers to sunlight sweetens them.

Oca - the taste test

Oca – delicious in stir-fries

Eaten raw, the oca tubers have a slightly lemony taste, which becomes more nutty during cooking. The tubers also lose their pink/red colour when cooked and turn cream instead. Oca can be cooked in the same way as potatoes and is perfect for adding to soups and stews. The leaves are edible too with a tangy lemon taste – add them to salads for a citrus twist.

Earlier this month we sent each of our trusty triallists a small batch of oca tubers to cook and taste and to let us know what they thought. We asked the testers to cook them in different ways and most tried boiling, roasting and stir-frying, while others microwaved or grated them raw into salads.

The verdict

Boiled oca mashed with butter is the best way, according to one of our testers. Others reported a very mild sweet lemony flavour, not dissimlar to sweet potato and a texture like swede. The tubers retained a bit of the nuttiness and a lot of the flavour. One tester said “Very tasty, would recommend them.”

Roasted oca didn’t far so well in the taste test – they cooked well, but the flavour wasn’t very distinctive and they tasted very much like roast potatoes.

Our testers were very keen to try them raw, either sliced or grated over salad leaves or mixed with fresh salsa. Prepared in this way they were crunchy, with a texture of radishes and “lovely and crisp”. The mild, light fresh flavour of lemon changed to a nutty/earthy flavour.

When stir-fried the tubers stayed nice and crispy and had more flavour when cooked and added a bit of colour. One tester thought they would be good in a vegetable chilli or curry. The flavour was ‘zingier’ and the tubers retained their crunchy texture.

Microwaved for 30 seconds, they went soft and the texture was a bit like a chestnut. The taste was stronger when cooked and sweeter and less earthy. The skin also had a slight fruity/acidic taste. Another tester said they were still crunchy but microwaving them seemed to bring out a sweetness that wasn’t there in the raw tubers.

Oca - the taste test

Oca leaves – add to salads for a lemony twist

A couple of testers fried them and one said “By far the best was fried! I fried them in a little oil and the taste was superb. They didn’t need salt, pepper or vinegar to taste and I found them as tasty or even better than potato chips.”

So the overall verdict is that lightly cooking oca tubers, whether stir-frying or microwaving brings out the best flavours. Here are some final thoughts from our panel of taste testers:

“Best eaten with other vegetables or salads to obtain best flavour experience, not on their own. I thought the stir fried option the best, but having said that I would equally add them to salads and will be trying them in soups and stews.”

“I didn’t realise oca was so versatile! In a way a bit like potato in that they can be served up in a variety of ways, but with a better flavour than potato.”

Oca is available to buy online here

Read our article on growing oca here


Rebecca Tute

Rebecca works in the Marketing department as part of the busy web team, focusing on updating the UK news and blog pages and Thompson & Morgan’s international website. Rebecca enjoys gardening and learning about flowers and growing vegetables with her young daughter.


Guest blogger Phillippa Lambert writes about growing Oca – a versatile and tasty vegetable.


A new vegetable crop for me this year is Oca (Oxalis tuberosa), along with Yacon, (a treat for next growing season), Oca is one of the ‘lost crops’ of the Incas, and a staple crop in Bolivia and Peru.  It is grown from tubers, much like potatoes, but is not related to them in any way, hence they are blissfully free from blight. Oca produces attractive yellow flowers set against prolific trefoil foliage, that acts as effective, and largely pest-free, ground cover. The only drawback is that Oca is tender (preferably started under cover in the spring), and needs a moderately long growing season to achieve a worthwhile crop.

Oca can be cooked like new potatoes (very tasty with a lemony tang), roasted in the oven, or even used raw in salads in much the same way that radish is prepared.

Oca roasted in olive oil and balsamic vinegar, with red onions and beetroot, dressed with soured cream

Oca roasted in olive oil and balsamic vinegar, with red onions and beetroot, dressed with soured cream

Oca and watercress salad

Oca and watercress salad

I started off my Oca in the spring from small chitted tubers, in the greenhouse in Root trainers.  As soon as the weather warmed up enough (early May on the Isle of Wight), I set them out in rows, 12″ between plants, and about 30″ between rows.  They require very little work during the growing season apart from keeping down any weeds before the foliage closes over, and some earthing up to increase crop yields.  An absolutely crucial piece of information is that Oca does not start to form its tubers until the days shorten in the autumn — it is day length dependent.  The key to a heavy crop is to keep the leaves protected from frost as long as possible — fleece may be necessary if early frost threatens — and only dig the crop about 2 weeks after the top growth has been completely killed by frost.

Oca, fleece-covered in late November, to preserve the top growth as long as possible

Oca, fleece-covered in late November, to preserve the top growth as long as possible

Storage is easy;  as Oca does not react to the light by going green, as potatoes do, simply sort the crop — the larger tubers for eating, smaller sizes for next spring’s seed, and place in paper bags in a consistently cool place.  Refrigeration is not necessary. Those for planting can be chitted in a frost-free, light position in early spring, (just like potatoes), and the whole cycle starts again!

Lifting the crop just before Christmas

Harvesting oca tubers

Lifting the crop just before Christmas

Washing off the tubers before storing

Washing off the oca tubers before storing

Washing off the tubers before storing

A selection of both colours

Oca tubers - A selection of both colours

A selection of both colours

Read more about Phillippa Lambert at

Phillippa Lambert

Phillippa Lambert is a landscape designer based on the Isle of Wight at a unique site in the Undercliff of the Island — a favoured microclimate sheltered by enormous south facing cliffs. In 2002 Phillippa and Stephen Lambert came across the ‘lost’ gardens of a Victorian mansion dating back to the 1820s, managed to acquire part of the site, including the walled garden and ornamental lake, and have since worked on their restoration. The result is not an ‘expert’ garden and does not try for technical perfection in any sense. ‘Make do and mend’ is the keynote — most plants being raised from seed or cuttings— and self-sufficiency is the motivation for all the growing in the walled garden. In essence, this site goes back to the philosophy of ancient gardens in sustaining the body as well as the soul. Read more at Lakehouse Design.

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