Meet GOB (Guild of Oca Breeders) 1356, harvested in early December. It’s a cheeky little number with attractively flushed red/pink skin and creamy white eyes. My chief tasters were pleasantly surprised by its sweet taste and refreshingly delicate, yet acidic endnote. They were also impressed with the soft, buttery texture and bite-sized proportions of these diminutive rosy tubers which can be eaten raw, boiled or roasted. They did, however, request baked beans with them next time.

I first detected my leaning towards ocaholism (a technical term) a few years ago when I bought five tubers of Oxalis tuberosa from Real Seeds because they looked interesting and different. I was attracted by their being unaffected by blight (as they aren’t related to potatoes) and their edible leaves (a bonus in a small garden containing even smaller children with a penchant for eating anything they came across).

What I didn’t realise was how they would brighten up my autumn days, introduce me to a plethora of other South American tubers, lead me to join The Guild of Oca Breeders and participate in a fascinating study of the habits of this lesser-known member of the oxalis family.

A Little Oca History

Oca originates from the Andean mountain regions around Peru and Bolivia, where it is still widely grown. It has been grown a little in the UK over the past 150 years, but has never been commercially viable due to limited yields. Its common name, ‘New Zealand yam’ (although it’s not a true yam from the genus Dioscorea), comes from its popularity as a vegetable in New Zealand where it was introduced around 1860.

The Guild of Oca Breeders

This dedicated group of breeders are passionate about breeding oca varieties selected for early tuberisation, thus creating a crop which will be less affected by declining light levels, falling temperatures and early frosts. Oca starts to form tubers around the Autumn equinox, which this year was 22 September. If frosts occur too soon after this date the foliage withers and the tubers stop growing, or even rot. In the same way that decades of selection is believed to have bred potatoes which thrive in the UK, the Guild of Oca Breeders hopes to use people power to select oca varieties which will give higher yields.

Tubers in pots to encourage early growth

My GOB oca went in at the allotment in June and has been growing away happily, unaffected by pests or disease, until I harvested it this week. Even the foliage and stems are interesting, with different habits and different colours ranging from light green, through dark green and pinks, to reds and purples. It really is a low maintenance crop, needing only occasional watering and protection from nibbling by deer on the allotment.

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The different colours and growing habits of my GOB Oca

The last couple of days have been spent happily washing, sorting, weighing and tasting the different varieties to ascertain which might be worth cross-pollinating when the cycle starts all over again next year. In the meantime, we’ve had fun exploring this Andean treasure in all its sensory beauty.

Some of the washed and sorted December Oca harvest

A Fun Family Crop

Oca has a number of attractions as an allotment or garden vegetable…

1. When chitted (not necessary, but ours sometimes chit of their own volition) they look like little aliens. Once I planted some out with my son and one of his friends (both aged about 5) and they were most intrigued. His friend came round for tea last week and still remembered planting the odd red tubers from two years ago.

Chitted Oca is a vegetable with personality

2. They come in a range of shiny rainbow colours – I’ve added ‘Bicolor’ to ‘Helen’s All Red’ this year as well as my 14 GOB varieties. Other varieties have delightful names like ‘Raspberry Ripple’, ‘Strawberries and Cream’ and ‘Occidental Gems’.

My favourite Guild of Oca Breeders varieties this year

3. They are a versatile, nutritious and tasty vegetable. Unlike potatoes, oca can be eaten raw (with a taste like a lemony cooking apple), although I prefer them cooked (good in stir-fry, mashed with or without potato or roasted.) With a Sunday roast, they add a delicious lemony note to other roasted vegetables, taking 20-30 minutes in the oven with a tiny drizzle of oil.

As with rhubarb, spinach and sorrel, oca leaves and tubers contain oxalic acid and therefore should only be eaten in small amounts and avoided by people who suffer from arthritis, gout and certain other ailments (for further information see the Plants For a Future Database). Tubers can be left in the light for a week or two after harvest to reduce the oxalic acid context and sweeten the taste.

If you like Oca…

You might also like to have a go with some of these other interesting Andean tubers. I’ll be trialling some next year, so look out for more tuber-related posts coming soon…

1. Yacon (Smallanthus sonchifolius) – related to sunflowers and Jerusalem artichokes. I currently have two yacon plants waiting in pots in the house, ready to go outside next spring.
2. Mashua or Peruvian Ground Apple (Tropaeolum tuberosum) – another tender Andean tuber related to garden nasturtiums with a peppery flavour
3. Ulluco or Papalisa (Ullucus tuberosus) – vivid coloured tubers with succulent, edible foliage. Another beautiful crop to harvest in winter and brighten any cold December day.

I’d love to hear from anyone who enjoys growing tubers – what do you grow and how has it been this year? If you’d like to read more about my adventures with more unusual and delightful plants, you can subscribe to the blog below: