Oca - Oxalis tuberosa

 
Oca originates in the Andes, where it is still an important food crop. It is easy to grow and is not fussy about soil types. Plants need little attention during the growing season and in the UK are generally unaffected by pests and diseases. They are not frost tolerant, however, and tubers develop late. Oca is therefore more suited to areas with mild winters. In the UK it grows well in the south and west and in coastal areas. We grow it on the west coast of Scotland where it crops well year after year.

In areas with early frosts, oca can be grown outdoors in bags of compost (one plant per bag) which can be dragged into a greenhouse at the first signs of frost in autumn.

Oca tubers will over-winter in the ground if buried deep enough, and sprout in spring. Even when you think you have dug them all up there will always be a few that pop up among the next seasons crops and these 'volunteers' can be dug up and replanted in a new bed. It is also easy to store tubers for spring planting - wrap them in paper and keep in the bottom of the fridge, or in the garden shed. You can also keep them in trays or boxes of slightly damp compost - better for large quantities.

In early spring, tubers will start to sprout. You can either keep them as they are until mid-April and plant them out in the ground (don't worry if some sprouts get knocked off - more will grow - and don't be afraid to cut them back if they grow too long) or pot them up individually in 9-11cm pots of compost and keep somewhere cool but frost free (This is the best way to grow small tubers). Wait until the worst frosts are past before planting outside. If plants do catch a night of unexpected light frost in spring, the leaves may get burned, but the plants will soon bounce back.