Winter pruning vs. Summer pruning
The main objective of Winter pruning is to develop and maintain a strong, well balanced, branch structure.
This is achieved by establishing dominant leaders (through apical dominance ) with lateral branches that are no larger than half the leader diameter.
Winter pruning generally promotes vigorous new growth , while Summer pruning retards growth - the new growth tends to be much less vigorous.
Pruning in Summer thus saves the tree from wasting energy when the unwanted new, vigorous, Winter pruning growth is later removed.
Summer pruning can control size and the shape of fruit trees, and - by increasing the movement of air through the canopy - help to control diseases.
Summer pruning also helps to maintain the critical balance between new vegetative growth and fruitfulness.
There are two basic pruning cuts :
Heading cuts are where terminal stems and branches are cut back.
Heading cuts remove the dominant apical growing tip and this releases the side buds to grow resulting in an unwanted, more dense, vigorous growth at the point of pruning. Heading cuts result in a thicker and denser canopy that will reduce light levels within the tree. Apical dominance then has to be re-established by thinning-out the dense new growths to establish a new dominant leader.
Thinning cuts remove stems or branches at their point of attachment. This results in much less vigorous regrowth (due to the retainment of apical dominance) and improved light penetration.
When making thinning cuts prune just outside the branch collar - this will lead to rapid wound closure and the prevention of decay in the main stem or branch.
When Summer pruning use mainly thinning cuts (rather than heading cuts) and prune to an outward facing bud.
Summer bearing fruit trees are best pruned as soon as possible after the fruit has been harvested
( providing the weather is not wet).
Summer pruning wounds heal rapidly - less chance of diseases entering through open wounds (important for apricot and cherry trees).
Summer prune for sunlight - open up congested canopies and allow light into the trees, this will help keep flower buds alive for next year's fruit crops.
Cut out completely all in-growing branches to open up the centre of the tree.
Prune crossing over branches and cut out all dead or diseased (gumming ) wood.
Much of the new growth made since spring can be cut back by at least half.
Once a system of summer pruning is established, very little winter pruning is required and a better balance between vegetative growth , flower development and fruit production is maintained.