Jian Liu, from Camberwell, has her own website, called Melbourne Foodforest, where she writes articles to help people to develop their own food forests. In late 2021, she published an article about why and how to grow oca. Here she summarises that article.
Oca is a root vegetable that you may not have heard of. It is a hardy, nutritious and tasty tuber which tastes quite similar to potato but is a little more nutty and (some say) lemony. It can be steamed and mashed, baked or fried, just like potato or, unlike a potato, it can be eaten raw. It has a low Glycaemic Index. As per the photo, it looks like a witchetty grub!
As a plant, it is hardy, easy to grow, highly productive and can be grown in part shade. The hardest part is finding some tubers to get started. It is a warm season vegetable which should be planted in late winter or early spring. Like potato, it is a perennial grown as an annual. It likes compost but not too much manure or nitrogen, as this promotes leafy growth over tuber growth.
As the plant grows, it is good to top up with compost as more tubers will form wherever the stems touch the soil.
Only harvest when all of the foliage has yellowed. This generally occurs around the shortest day of the year in winter. Dig around carefully with your hands to unearth the brightly coloured tubers. Wash, clean and dry in the sun, then cure in the sun for up to a week for sweeter tubers. Then store away somewhere airy and dry, like a pantry or in a shed.