- Author: Ben Faber
A recent trip to Spain was an opportunity to look at their cherimoya production practices. One of the most interesting is their ability to manage the tree through pruning to produce fruit off-season (in spring) when the prices are the highest. IN California our low period of production is in the summer. The climate in Spain along the Mediterranean coast is warmer and more humid than coastal California, so most tree crops are about two months advanced in their production. So in the text I refer to a period when something is done and then follow it with another date. The one in parenthesis is the probable time in California if the date in Spain is used. So, to produce fruit in spring (summer) in March/April when prices are high:
Remove all shoots from the previous year in March (May)
With the new shoots, prune them back 6 inches in length around July 15 (September 15)
Pollinate the flowers that are produced in the period of August to September (Sept/Nov)
Pick fruit in March/April (June/Aug)
Advantages:
Fruit is produced when prices are higher
Generally fewer seeds than at other periods
In some cases there is higher sugar content in the off-season frui
Disadvantages:
Not always consistent with all cultivars
Off-season fruit often has black spots in the pulp
May see increased leaf drop
In some cultivars, the skin is more prone to abrasion, and this is already a very delicate fruit
There are other fruit species that fruiting date can be manipulated by pruning, such as evergreen blueberries, guava, lime, mango and carambola (star fruit). Always it is to find a better market for the fruit.
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- Author: Ben Faber
A general rule of thumb about pruning trees is that only healthy trees should be pruned. Pruning is a devitalizing practice that comes at the expense of the roots. If an avocado has root rot, make sure the tree has been treated with one of the phosphite products to get the root system healthy. A common pruning method is stumping to 3 feet and allowing regrowth to occur. A common phenomenon after stumping is that the tree puts on vigorous growth for two or three years and then collapses. All that canopy regrowth was coming from a large root system that was brought into balance with a smaller canopy. Energy is diverted from the root to fight off disease. Gradually the root system gets out of balance with a larger canopy that it can no longer support. Often when a severely impaired root system tree is pruned, it often does not have energy to push a new canopy and the tree dies. Make sure you only prune healthy trees.
- Author: Ben Faber
In the past avocados were rarely pruned. In fact, if the trees got very big, growers would stump them down to 3-4 feet and then let them regrow. This would often be a disaster, since the trees rapidly grew to stupendous sizes again. They also might regrow then suddenly collapse, because all that regrowth was coming at the expense of energy being sent to the roots. If the roots were compromised by root rot, they would then not have the energy to fend off the disease. So by bringing the canopy into balance with a sick root system that was continuing to die and was not being fed by a big canopy, the root death would accelerate and when the canopy and root system became imbalanced again, the whole canopy would collapse and the tree would die.
Also, this wild regrowth was wild and hard to manage. The adage of “prune avocado trees cautiously” was heard round the avocado community and as a result many growers would not do anything. The trees growing larger and larger and larger with the fruiting canopy going higher and higher and higher and picking costs and liability going up. Tree thinning was practiced, where every other tree would be removed so that light could penetrate into the orchard, encouraging more fruit production and slowing tree growth. But they would still grow and another thinning would be needed. The original commercial ‘Hass’ orchard in Carpinteria started out in 1954 with 140 trees and 40 years later was down to 17 trees and was still productive, but they were monsters that were finally felled by root rot.
Many commercial avocados are now routinely pruned to keep the trees short, so that harvesting costs and other tree maintenance expenses are reduced. Also more light shines into the trees, so that more fruit is borne on the lower branches. Light or minor pruning can be done any time of year to correct imbalances or limb breakages. However, major or heavy pruning should only be done in the early part of the year from January through April. Avocados flower and bear fruit at stem terminals, so if you give the tree and buzz cut (heading cuts), all the flower terminals will be cut off and there will be no flowering the following year. It also leads to an explosion of water sprouts that result from bud break up and down the branch because the terminal bud which control the buds lower down have been removed. Naphthalene acetic acid (TreeHold) painted on the cut end can be used to restrict some of this wild bud break.
Whenever possible, thinning cuts should be made, where the branch is removed back to a subtending branch. This results in much less wild growth. Also when there are buds that start growing into water sprouts, they can be nipped back to force lateral growth. These laterals will then slow down the growth of the sprout and the side terminal buds will also be able to grow and transition of flower buds later.
Work in Carol Lovatt’s lab at UCR has shown that terminal buds need a certain maturity to flower and the transition from a vegetative bud to a flowering bud occurs sometime in late summer/early fall. If pruning is done in July, there is not enough time for the new buds to mature by August and there will be no flowers from that branch the following spring. New vegetative buds formed on growth from spring will often have enough maturation time to make the transition to flower buds, resulting in flowering the next spring.
Again, light pruning can be done at any time of the year, but removing terminals is removing potential fruiting wood. Therefore, if heavy pruning is needed, it is best to remove one branch at a time. To reduce the height of a tree, cut out the tallest branch one year, the next tallest branch the following year, and so on until the tree is down to the height required. The process may take three to four years. By reducing the height over several years, the tree is put under less stress, less disease is likely to occur and fruit production is not drastically reduced. Pruning the sides of the tree should be done in the same way. Prune off a side branch that most impinges on a neighboring tree one year, then the next worst offender in the second year, and over the years continue this process until there is light all around the tree.
If pruning creates major open areas in the tree to sun-light where there once was shade, the exposed branches should be painted with white latex paint diluted with water so that it can be sprayed on. It needs to be white enough that it can reflect sunlight and avoid heat damage that can cause sunburn. Sunburn can utterly destroy all the work that has been done.
If the trees are really monsters, the only real alternative is to bring the whole tree down. But not stumping, rather scaffolding where much of the structure is maintained. This is where the tree is brought down to as high a height as is convenient and safe. By cutting the tree to a height of 8 feet or so, there is not so much rank regrowth because a greater portion of the tree is retained. Also many times there are leafy branches that remain that will flower and fruit and slow the wild regrowth. Water sprouts that form should be headed back to force lateral growth that encourages stems that will flower, which will also slow the wild regrowth.
And one last warning. Do not. Do not. Do not. Got it? Prune sick trees. If the roots are compromised, the regrowth is going to be hard on the roots. Get the trees perked up with one of the phophite products so that they are ready to go through this process. You may have to wait a couple years to start the pruning process until the trees are in shape for the rigors.
Image: Don't make cuts like this.
- Author: Ben Faber
Gary Bender has made his manual on avocado production available on his website. And it's free. Take a look at it to see if you might be missing something in your orchard:
http://ucanr.edu/sites/alternativefruits/?story=237&showall=yes
- Author: Scott Van Der Kar
Training
At planting (preferably in spring), if trees have an unbranched trunk greater than 2 feet tall, the tree should be headed back. This procedure should induce other buds along the trunk to shoot. Always remove leaves at positions where new shoots are required. Leaf removal is important since the petiole covers the bud and prevents bud break. Lower branches with weak crotches (less than 45°, or greater than 90°) should also be removed.
During the first summer one shoot is encouraged to dominate by lightly pinching back the other shoots and loosely tying the main shoot to the stake. This shoot (leader) will become the tree trunk.
About every three months some pruning can be performed to rapidly create a large framework. Select primary scaffolds beginning with the lowest facing the prevailing winds. Select additional scaffolds, upward along the leader at intervals of several inches or more, to form a spiral pattern around the trunk.
Head these scaffolds to 18 inches in length to maintain the central leader. Remove strong unsymmetrical growth not required as the leader or scaffold branches. Also remove any limbs with weak crotches. The position of scaffold branches can be selected by removing a leaf in the desired position, thereby uncovering the bud.
In subsequent years continue to select primary scaffold branches until four to six are present. Then allow the leader to become the topmost scaffold. Continue to head back scaffolds. Each time they are pruned, they tend to produce two strong end shoots. One or two weaker shoots might also form, these should be removed. As the pattern continues, the tree will gradually open up.
Pruning Bearing Trees
How heavily to prune depends on the variety and the tree's vigor as judged by the tree spacing, soil and climate. Unpruned trees initially bear substantially more fruit, but as the canopy becomes crowded, the inside becomes devoid of leaves and fruit, and production moves to the outside of the canopy. As a consequence, it is more difficult to pollinate and harvest, and more damage to fruit from branch rubbing is encouraged.
From the third or fourth year from planting the goal should be to prune about 6 to 8 inches from the new growth. This pruning should be done in the spring prior to bloom. If there is excessive growth during the summer, a light fall pruning may be necessary. However, heavy cropping will retard vegetative growth.
Each year branches that are crowding the center need to be thinned out along with dead wood. Fruiting wood that has grown more than 18 inches from the scaffolds also needs to be headed back to prevent the limbs from breaking with the weight of fruit.
The best level of pruning is going to be determined by experience. The severity of pruning will vary according to the lateral growth each season and cropping level. Other guidelines are to avoid too much shading within the canopy and to allow enough room between branches so that fruit will set clear of limbs and other fruit.
This is an abridged version of the pruning article in the California Cherimoya Association Handbook
Cherimoya fruit