I have spoken of sweet potatoes and of Jerusalem artichokes. Now it is time for the exotic and strange but delicious oca tuber. Native to the Andes from Venezuela to Argentina, and introduced to Polynesia and New Zealand as an important crop, oca is eaten raw, parboiled or roasted. The 4-6 inch tubers have a tangy flavor with nutty overtones and often sport amazing color (colors range from deep red or even black to boring tannish potato-colored). They are super-delicious with bacon. The foliage is similar to the familiar clover leafed plant so popular on St. Patrick’s Day but more succulent.
In Tucson, most Oxalis species are grown in winter. These guys don’t like temperatures over about 85 degrees. But you will want to cover them on cold, frosty nights. They like cool weather but they don’t necessarily want to get hammered by the frost.
The like nice, loose, rich garden soil, and as with most root crops don’t want a lot of nitrogen.
Wait until the plants go completely dormant, and lift tubers. Store for next year’s crop in sandy soil, in a bag, in a coolest spot in your kitchen. If they start to grow in the bag, plant them in a pot in your house, but don’t put them outside until late september.
‘Slips’ can be taken in a similar way as with sweet potatoes.
Roots start to develop from the Oca tuber itself, but what makes this method so easy is that roots also tend to form spontaneously at the base of the shoots if they are in contact with soil. It’s a simple matter to gently break away the shoot, roots and all, and install it in some sandy compost.
These are best planted alone. Let them do their thing through the season, and when it warms up, lift tubers and store in cool, dry place, in a bag of sand is good. You can leave them in the soil if you can shade it with a lot of mulch and only water when totally dry or when you start to see growing activity. But really, I suggest lifting tubers and storing them.
When harvesting oca roots, let them sit in a cool place for a few days until tender (and for the oxalate crystals to decrease). Only lift the roots you are going to eat.
US sources for other varieties are difficult and sporatic at best. The only good source online is from England (The Real Seed Catalog) and they won’t ship to the US. But if you have a good friend in England, you might get some help.
In Polynesia and New Zealand they are hard-headed and call these yams. Here is one way to prepare them.
And here is some German dude showing you his plants and how he cooks them.