Plant Doctor Archive

Growing yams and leeks

I TRIED to grow yams this past year. They grew but were covered in deep fissures and were basically unusable. I wonder if it was lack of water during the dry season. Could you also advise me on the soil type as well as fertiliser and water requirements for both yams and leeks?

YOU may be interested to know that yams are a species of oxalis, closely related to the weedy varieties. But there are many oxalis species that are not weeds - some are attractive foliage and/or flowering plants and in the case of Oxalis crenata (yam or oka) they produce edible tubers.

Yams grow best in light, well-drained soil but need good moisture in summer to crop well and to avoid cracked tubers. However, overly wet conditions, especially in heavy soils, could cause tuber problems too.

They are tolerant of slightly acid soils, so you probably don't need to apply lime. Mix a general fertiliser such as Gro Plus Complete Plant Food into the soil at planting time (late October to early November) and then some more as a side-dressing when you mound the soil up around them as they grow, in much the same way as you would with potatoes. Check the fertiliser label for application rates.

Leeks grow best in free draining soil but also require good moisture, especially in the early stages of growth after planting in mid to late summer. Being a leaf vegetable, they need good nutrient levels to grow well, so mix in a general fertiliser at planting time and apply a side-dressing about six to eight weeks later.

A leeky tip I learned many years ago was to poke a hole in the soil about 15mm wide and 100-120mm deep and drop in a pencil-sized leek transplant with its roots neatly trimmed to about 10-15mm. Then just give a light watering into the hole - don't fill it with soil. The young leek will soon root into the soil at the bottom and the cylindrical hole will act like a mould to help form a leek with a lovely straight white stem.

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