The world has many different types of sweet potato but the one we have made our own in New Zealand is the kumara. Had we grown them this year, we would be looking to harvest around now. But we didn’t so we will be buying them instead. Kumara are a warm climate crop so the further south and the further inland you are, the more problematic they are to get through. They need somewhere between five and six months of warm weather (preferably in the low 20s) to set plenty of tubers. You can help by planting in black plastic and using cloches early in the season. They are easier to grow well if you are right on the coast and gardening in sandy soils which heat up. However they don’t want to bake and dry out in midsummer.
Kumara will sprout like potatoes over winter so you can cover the tuber with soil or straw in early spring. That tuber will put out many shoots which can be pulled off and planted out when big enough and when roots have started to form. They don’t like any frost at all, so in inland or cooler areas, they can be started in pots for planting out in mid November. Plant them about 40cm apart in the hottest and sunniest spot in your garden and watch them r-u-n. It is easier to understand when you know they are close relatives of convolvulus. Besides keeping a little water up to them all summer, the other care they need is to have their wayward vines lifted every week or so, or trained over a wall or path. If you don’t do this, the vines start to send roots down along their length and a plant which is using its energy to create a whole lot of new roots is not developing good tubers. Harvest when the foliage turns yellow and store in dry conditions about room temperature.
First published in the Waikato Times and reprinted here with their permission.