Plant Doctor Archive

Growing yams

CAN you tell me the best time to plant and harvest yams and what conditions I should grow them in?

YAMS, also known as oka, are a type of oxalis of which there are many different species and varieties. Some of them are difficult-tocontrol weeds, others well-behaved, attractive flowering ornamentals, while the yam (Oxalis crenata) provides us with tasty tubers for the dinner plate.

The best time to plant the tubers is after the soil has warmed up somewhat, in spring, around late October to early November. Treat them much the same as you would potatoes, creating mounds to improve drainage. They grow best in light, sandy, free-draining soil and can struggle to be successful in damp, heavy clay. They prefer good fertility, so apply a potato fertiliser at planting time and then again about 8-10 weeks later. They are slightly acid-tolerant, so in normal conditions shouldn't need any lime.

Yams seldom suffer from any pests or diseases, but in dry summer conditions you'll probably have to put some effort into watering them regularly to get a decent yield of tubers. Six months or so after planting (March-April) you should be harvesting tubers.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.