Kumara are perennial vines that are propagated vegetatively, either by shoots from the tubers or cuttings from the tips of the growing plants. When placed in a warm moist medium (in August), shoots form along the sides of each tuber and take root, and can then be broken off with their new roots and planted straight into the garden. Kumara commonly carry serious viruses, and growers who keep their own seed over the years need to develop a system for minimizing this problem. Kumara with very dark patchy skin often have a virus, and it will affect their keeping qualities seriously.

Joseph Land, our kumara curator, minimizes the problem by taking cuttings from the first tips that appear from the tubers each spring and rooting them in a seed tray and then planting them out in a separate block. The tubers from this block are the ones to save for growing tipu the following spring. This is the traditional method for keeping kumara healthy. It is well known that the strongest growing tips are the healthiest and best places to collect virus free material.