Tall spindle plantings produce high early yields and are simple to train and prune.
There are numerous ways to grow apple trees, and many of them can be successful, says Dr. Terence Robinson, research horticulturist with Cornell University, New York.
“As I travel around the world, I see a number of successful modern systems,” he said.
Robinson categorizes training systems as freeform (tall spindle, super spindle, and biaxis), semiorganized (Solaxe), and organized (V-trellis and vertical trellis).
The tall spindle, which is the system Robinson favors, has trees planted 3 to 4 feet apart with 11 to 12 feet between rows. The super spindle, which also has been successful in the United States and other parts of the world, has trees planted 1.5 to 2 feet apart with 10 to 11 feet between rows.
The biaxis, also known by the trade name Bibaum, was developed in Italy. Trees are planted less densely, about 4 feet apart in the row, because each tree has two axes rather than one central leader. Rows are about 11 to 12 feet apart. Twin leader is another name for this type of system.
The Solaxe system is a more formal system than the spindle. Although Robinson is not a proponent, he considers it a viable system that is based on good physiology. Trees are planted 3.5 to 4 feet apart with 12 to 14 feet between rows.
The V-trellis, which is common in Washington State, has trees planted 2 to 3 feet apart, but the rows are further apart than with other systems because of the V. Trees lean to alternate sides, and limbs are precisely positioned.
The vertical trellis has trees spaced more widely at 4 to 5 feet apart because limbs are trained along each of the five or six wires, but there is usually only 8 to 10 feet between rows.
Robinson said all the above systems can be profitable and growers could do well with any one of them as long as they understand the system. However, he favors the tall spindle for a number of reasons:
High early yields: It produces high early yields, with growers achieving up to 3,000 bushels (145 bins) in the first five years as well as high yields at maturity. New York growers are harvesting 60 to 90 bins per acre, which was unheard of some years ago. “We can obtain higher yields than we ever thought possible,” Robinson said.
High fruit quality: Fruit quality is high because of good light distribution in the trees.
Easy to teach: Pruning and training are simple, so it’s an easy system to teach to unskilled workers. After limbs are tied down in the first year, little further training is needed compared with organized systems. Branches bend naturally with the weight of the fruit, which leads to a balance of vegetative growth and cropping. The system’s simplicity makes it adapted to partial mechanization.
Lower unit costs: The combination of comparatively high yields, high fruit quality, and low training and pruning costs result in a lower per-box production cost.
The ideal tree for the tall spindle system has a caliper of 5/8 inch and at least ten feathers and is not headed at planting. Robinson said some growers use sleeping eyes because they’re much cheaper. The price difference between the various types of trees reflects their value, Robinson said. If everything goes right, sleeping eyes can be successful, but they are less likely to produce high early yields. With a feathered tree on a precocious rootstock, the entire planting can be paid for by the crops in the second, third, and fourth leaf.
For the support system, Robinson recommends a three-wire trellis with a bamboo stake for each tree.
Yield targets with the tall spindle are 10 bins an acre in the second leaf, 25 in the third, 50 in the fourth, and 65 in the fifth.
Robinson said it’s critical to tie down branches in the first year, otherwise the tree will be relative short as the branches will compete with the leader and become dominant and upright and need to be cut off. When the branches are tied down, the tree is taller and more slender with smaller feathers and there is no need to prune, which would invigorate the tree, so the trees settle down quickly.
When the trees mature, there are three simple pruning rules:
- Limit the height of the tree by cutting to a weak, fruitful side branch. Trees should be 9 to 10 feet tall.
- There are no permanent limbs. Each year, during the dormant season, remove two or three branches over ¾ inch in diameter using a bevel cut to encourage replacement limbs to form.
- Simplify each remaining branch so that it is long and pendant with no side branches. Side branching creates too much shade in the canopy.
- Summer pruning can be done mechanically by shearing the sides, which dramatically reduces pruning costs. Because big branches are not being cut, there is no significant growth response.
Dr. Terence Robinson discussed this topic during the International Fruit Tree Association’s annual conference in Pasco, Washington, February 2011.