Many articles have been written on how to prune fruit trees or crops. Opinions as to the best methods of pruning are diverse and varied as the number of authors having produced them. However, if you look closely at fruit crop pruning, and follow some basic principles, it really is simple. In my opinion there are five key principles which must be followed. They are:
1. Understand the crops growth and fruiting habits
2. Visualize your desired results
3. Determine and achieve a balance between vegetative and fruitful growth
4. Time your pruning for best results
5. Prune to a pattern
These five points are further elaborated below. Irrespective of the fruit crop you are pruning, these five points are directly applicable. Examples of application to a range of crops are given as each of the five principles are elaborated on.
Understanding the fruiting habits is not always easy. Some crops such as grapes, kiwifruit and passionfruit are relatively simple, with fruit produced on one-year-old canes and spurs. This allows the grower to clearly define fruitful from non-fruitful wood and plan pruning regimes accordingly. Other crops are trickier such as apples, pears and persimmons with fruit sometimes produced on one-year-old wood, but often on 2 year old and older wood. Determining what to prune and what to leave will have an impact often for upwards of 7-10 years. Even within some crops, such as apples, you have distinctive fruiting and growth habit differences.
Most pruning undertaken in commercial orchards works directly against the trees or vines natural growth habits. So, how can we harness the natural growth habit of a tree for our benefit?
There is no better way to visualize your desired results than to see a perfectly pruned tree. Visit top gardeners to see well-pruned trees. If you can picture in your mind the results of good pruning then the pruning itself will be easier. This takes on particular importance when pruning young plants. Being able to visualize a desirable tree shape for a mature tree provides significant assistance to your pruning decisions on the young tree. Knowing which shoots and branches to leave on young trees to form the basic tree framework is critical, as these shoots are unlikely to ever be removed during the life of the tree.
Achieving a good balance between vegetative and fruitful growth is only partially influenced by pruning Factors such as soil type, climate, variety, and nutrition also play critical roles. On vigorous growing plants the desire is usually to increase fruit carried to slow down the vegetative growth. Techniques, such as removal of strong “water-shoots” or “suckers” on apples, girdling and even regulated deficit irrigation can be used to slow downvegetative growth. The response from slower vegetative growth is usually more flowers and increased fruitfulness. Selective pruning to remove vigorous, less fruitful shoots and to retain less vigorous shoots can assist in swinging the balance from vegetative to fruitful production.
Good timing of early summer pruning on most fruit crops can significantly reduce late summer and winter pruning requirements. Careful pinching out of undesirable growth such as “water-shoots” in spring has many benefits.
Firstly, growth is reallocated to more desirable parts of the tree such as the apex or more horizontal fruiting shoots.
Secondly, the pinching out of green shoots in spring is fast compared to lopper pruning in winter.
Thirdly, green woods heal faster than hardwood cuts, decreasing disease risk.
In some crops, poor timing of pruning can have a major impact. An example of this is kiwifruit, where late or no summer pruning causes excessive shoot tangling. This leads to difficulty with access into and around the orchard and can more than double winter pruning costs.
Following simple rules will assist in increasing pruning efficiency. Some to follow for apples are:
If you are working with a gang of helpers, pattern pruning is even more important. Having each worker focused on one to two activities only will result in greatest efficiency. Using the above pattern for apple tree pruning with a contact gang would see one person focused on removing dead and diseased wood, the next focused on tree structure, then one to two people working on removing old wood and water shoots and finally someone attending to the detail.
In summary, if you understand the growth habits of your tree, know in your mind the results you desire, achieve balances, time your pruning well and work to a pattern you should successfully prune your crop. The result should be good looking trees with high yields of quality produce.
On crops where the balance is too far in favor of fruitfulness effort will be needed to increase vigour. A good example of this is on BRABURN apples, which tend to fruit early. If over-cropped early in their life the trees fail to achieve a good size. Small trees can carry as much crop as larger trees. Similar problems can occur with mandarins. Sacrificing a crop or part of a crop on small trees to achieve a more desirable framework is preferable to ending up with small old trees carrying small crops. Crop thinning in this situation usually has a larger effect than pruning. On apples retaining strong apical dominance (top of the tree growth) is essential to maintain vigour in weaker varieties. As a last resort, if pruning and thinning fails to restore vigour, nutrient kicking the trees with a product such as Urea is a possibility.