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Foodwise, there have been a lot of good things to come from South America. Tomatoes, green beans, chillies and, of course, potatoes all have their origins in that part of the world. But there are still more crops with a long history of cultivation across South America that have yet to catch on with growers around the world.

Like the potato, oca (Oxalis tuberosa) is widely grown in the Andes for its edible tubers. It’s especially popular in Bolivia and Peru. I have a theory that oca may well be one of Paddington bear’s favourite foods. Marmalade sandwiches are just easier to come by in London because, unlike the potato, oca has yet to become a regular feature on the plates of European diners. But it might only be a matter of time, as over the last few years more and more gardeners seem to be growing this ‘new’ crop. Good news for Paddington…


Oca has a lot going for it – it’s relatively easy to grow, has few pests and is tasty and nutritious. The only down side seems to be the need for a long growing season, because the tubers don’t start to form until the days become shorter in the autumn.  Although I liked the idea of an oca harvest, I wasn’t sure if there would be enough time and sunshine between the arrival of shorter days and the first frosts for a good crop to develop in a Yorkshire garden. So, reluctantly, I decided to leave the oca growing for another year… and possibly another location.

Potted oca

Not long after I’d crossed oca off my growing list, this year’s Seedy Penpal parcel arrived.  A little box full of interesting and unusual seeds promising lots of colour and bountiful harvests from the garden. The parcel came from Emma Cooper, a gardener and ethnobotanist who knows a huge amount about plants and their uses. Emma writes about the plants she has studied in an entertaining and accessible style – have you seen her blog? Among the seed packets that Emma sent, was an envelope with some small, pink oca tubers inside. So no more excuses, Yorkshire climate or not, I was growing oca this year.

Oca foliage

And I can honestly say that oca is easy to grow. I started the tubers off in pots stood on the greenhouse shelf. The plants are tender, but with a bit of protection they got off to a good start and were soon producing clover-like leaves. My plants tolerated living in pots that were probably smaller than they were hoping for, along with an erratic watering regime until we moved house in July. Only then were two of the plants given space in the ground – the third was planted into a large pot that could be moved to a warmer spot to prolong the growing season when the frosts arrived.

Once the tubers were growing, maintenance was minimal. The potted plant got a (roughly) weekly feed at the same time as the tomatoes and chillies. The oca grew to form healthy mounds of foliage dotted with small yellow flowers – all very ornamental.

Oca flower

I held off digging up the tubers for a couple of weeks after a first hard frost had turned the leaves to a mushy mess – I’d read that they get bigger even after the foliage is killed by cold. Well, they didn’t get very big… maybe I dug them up too soon, but I was worried about the low overnight temperatures that were forecast. Lots of tubers, but most of them are pretty small – I wasn’t expecting anything the size of potatoes, but they are more like big broad beans. Lack of size is made up for by the flavour. They have a nice, lemon tang to them – a bit like the slightly sour lemon flavour of sorrel.

Cut tuber

I roasted the first lot of tubers, and countered the lemon flavour with some honey and a good sprinkling of salt (the honey could easily be replaced with maple syrup to keep things suitable for vegans). First reactions from the rest of the family were mixed – from a flat refusal to even try them, to a request for more please. I’ve saved some of the fattest tubers to plant next spring so, weather permitting, there will indeed be more.

Roasted oca

Roasted Oca

about 270g oca, washed

1½ tbsp. extra virgin olive oil

chilli flakes, to taste

1 tsp runny honey

sea salt

Heat the oven to 200oC, 400F, gas 6.

Cut any large oca tubers in half lengthways and put the whole lot in an ovenproof dish. Toss the tubers in the oil and chilli flakes until each one is covered with oil and roast until they are tender. Add the honey and salt to taste, stirring gently to coat all the tubers. Taste and add more chilli flakes if you want more heat.