Our established black grape produces a lot of large leaves and cane growth. Pollination and fruit development is slow. How much leaf and cane pruning and at what stage should it be done?
Grapevines in New Zealand are incredibly vigorous in vegetative growth compared to those grown in most European countries and so require hard pruning in winter.
Large leaves prevent sunlight from reaching developing grapes and should be removed regularly. Throughout the growing season also shorten back some of the vegetative growth to allow for better fruit formation and production of large bunches of grapes.
Prune in winter when all leaves have fallen off the vine. If the main leaders on the grapevine are established, prune to reduce lateral growth back to two nodes (where a shoot will grow from in spring). The growth from these nodes will produce grapes the following summer. If lateral growth is too crowded, thin this out to provide space for developing fruiting wood.
Monitor your grapevine in early spring as new shoots can be quite frost tender and therefore damaged if there is a late frost in your area. To lessen the threat, cover the vines with a frost cloth in late August through to September.