HOW TO PRUNE AVOCADO TREES
Excerptecl from article by ROBERT G. PLATT
California Agriculture Service
Pruning avocado trees may-
* Control the height of tall varieties
* Correct poor growth habit.
* Make orchard operations easier and cheaper
* Prevent wind damage
* Regulate severe alternate bearkng
But it may also-
* Stunt the full growth of the tpees
* Reduce the yield
* Stimulate the growth or foliage at the expense or fruiting
* Make trees susceptible to frost injury
SO--- PRUNE ONLY WHEN ABSOLUTELY NECESSARY.
Most avocado trees need little or no pruning. Whenever possible, allow trees to develop naturally and thin out the orchard by re-moving trees whan it becomes overcrowded. You will avoid disturbing the balance between foliage and fruiting wood which is essential for high yields. An abundance or foliage, which manufautures rood for the trees, keeps fruit vigorous. if this food supply is reduced by severe pruning, yields will suffer. On the other hand, high-yielding trees also need a healthy proportion or fruiting wood. if fruiting wood is trimmed back severely, foliage growth will be stiunilated at the expense or fruiting. For highest yields, a bal-ance between foliage and fruiting wood must be maintainede Often this is best achieved by allowing trees to grow naturally.
WHEN PRUNING IS NECESSARY
For various reasons you Ray rind that some pruning is necessary. if so, follow these simple rules:
1. Prune sparingly. Remove as little green wood and as few green leaves as possible.
2. Avoid pruning in the late summer and early fall. Pruning at these times will stimulate vegetative growth and may make trees susceptible to frost injury.
3. Make pruning cuts as close to a lateral branch as possible. The greatest growth stimulation is nearest the cut. If you remove large branches you will stimulate vegetative growth over the entire tree.
k. Cover pruning wounds which are 3 inches in diameter or larger with a water emulsion asphaltum paint or its equivalent.
PRUNING YOUNG TREES
Standard budded nursery trees are pruned heavily by the nur-seryman when they are dug. They may be planted without further pruning. If they lack vigor, or if they fail to start, cut them back heavily. Make this cut 6 to 8 inches above the bud union. After growth begins, allow the trees to grow as fast as possible without further pruning. If you are planting tip grafts rather than budded nursery trees, no pruning will be necessary.
TO CHANGE GROWTH HABITS
Occasionally you may find that a young tree is growing tall
without branching, growing sideways, or making an unbalanced top.
You can correct these conditions by cutting back the tip of the
unruly limb or trunk, or by staking the tree. However, avocados
grow irregularly, and most trees will develop a better structure if they are not pruned at all. On the other hand, the height or some varieties, Bacon, Zutano, and Anaheim, for example, makes picking difficult and costly. To prevent the upward growth, pinch back the terminal bud of the upright shoots while the tree is young. Repeat this after each growth flush during the first few years. The tree will spread out to the sides and develop a compact form.
TO PREVENT WIND DAMAGE
In areas where winds are heavy and frequent, keep trees low and stocky. You will have to cut back frequently to achieve this growth pattern. Begin training the trees when they are young; otherwise drastic cutting is needed. You may have to experiment with your own trees to establish the best pruning methods.
PRUNING MATURE ORCHARDS
1. To make cultural operations easier and less costly and to pre-vent accidental breakage.
2. To remove dead wbod.
3. To regulate severe alternate bearing.
4. To continue control of height after trees reach maturity.
5. To prevent natural breakage.
TO MAKE CULTURAL OPERATIONS EASIER
Irrigation practices. If you use low head sprinklers for ir-rigation, you may need to prune some of the low-hanging branches which interfere with good water distribution. Keep pruning to a minimum; heavy cuts on low branches force growth upward.
Cultivation and mowing of weeds. If you pratice cultivation or mow weeds, you may rind that some of the low-hanging branches interfere with either of these operations. Prune the low branches rather than risk breaking them off accidentally with cultivation or mowing equipment. Again, avoid heavy cuts.
TO REMOVE DEADWOOD
While removing deadwood is not essential, it may make picking and pest control easier. In coastal regions, removing deadwood may help prevent Dothiorella rot, which causes fruit to decay when softening.
TO REGULATE SEVERE ALTERNATE BEARING
Light pruning may regulate severe alternate bearing and increase the fruit size of some varieties. Pruning of one such variety, Nowels, resulted in a more consistent production over a four-year period. Shoots extending beyond the general contour of the tree were removed in February of the "on-crop" year. The effect of this type of pruning on the production habits or other varieties is not known.
TO CONTROL THE HEIGHT OF TREES
Fruit is easier and cheaper to pick if it is near the ground. The most economical height for a tree will depend upon the price of fruit, the amount of fruit borne in the top, and the cost of picking it. Although height control must be started when the trees are young, regular light topping- annually or semiannually- may be necessary when the trees are mature. If you are careful to avoid severe pruning, the fruiting capacity of the remainder of the tree will not be affected. If you head back tall trees, be sure to thin and cut back the new growth whieh follows. Otherwice the trees will soon reach their original height.
TO PREVENT NATURAL BREAKA GE:
Pruning to prevent loss of crop from natural breakage--- such as that caused by weak or over-loaded limbs-is of doubtful value. In most cases, even a severe break would result in less loss of fruit and fruiting wood than the loss from pruning. Vigorous trees will fill in severe breaks within a short time.
Your farm advisor will be able to give you further specific adviee about pruning youn~ trees and mature avocado trees in your specific area and for your individual variety.