Apple trees are pruned in the early spring when trees are dormant. The purpose of an apple tree is to produce large, healthy fruit that is easy to pick.
Apple trees are usually pruned in one of three ways; central leader, open center or modified leader.
When the central Leader which is the main stem, is not cut back, the tree will grow to its maximum height, making it hard to pick fruit, unless the top is grafted to semi-dwarfing rootstock.
In the open center or vase is style of pruning the central leader is removed at 30 – 26 inches (.75 to 1 metre) from the ground. Low side branches are pruned to grow tall and wide with an open center. In colder areas, open centre often results in sunscald from the heat of the early spring sun reflecting off the snow.
In the modified leader pruning method the top of the central leader is removed once 7 - 12 strong lateral or side branches have formed.
Removing the top of the leader reduces the tree’s height, encouraging the tree to spread outwards. This method is common on the prairies unless he rootstock is semi-dwarfing.
In the modified method, young trees are trained to a central (might be modified) leader with branches radiating in 4 directions; like an X. Ideally there should be 3 different levels of branches growing from the main leader. Each level should be at least 6 in. (15 cm) higher or lower than other branches.
Space between the branches insures that air circulates throughout the tree and branches do not rub. The tree is also pruned in the shape of a pyramid. Shorter branches at the top, ensuring the bottom branches receive sunlight.
When pruning apple trees, start by removing all watersprouts, suckers and dead wood. Water sprouts are new branches that grow 2 or 3 feet upwards in a season. They are easily identified as they do not have any side branches. If the sprouts stop growing in August they will survive the winter, otherwise they winterkill. Water sprouts that grow for more than one season, grow into the tree, rubbing against existing branches.
Suckers are new growth that comes from the roots not the grafted part of the tree. If left intact, the suckers will outgrow the graft using all the nutrients, eventually killing the grafted stock
Next eliminate crossing branches. Remove the one with the least desirable characteristics; pointing towards the center of the tree, torn bark, weak angle or smaller in diameter.
Remove narrow angled branches as they produce weak unions and are likely to split under stress of a crop of apples or a heavy snow.
On young trees, branches can be trained to grow at a wider angle. Pull them downwards with a string attached to the ground or weight them down with a milk jug. Slide the handle of milk jugs on the branch then add enough water to cause the branch to go downwards to the desired angle.
Leave the weights in place for a year or so until the branches hold the desired shape. Remove all branches that hang downward under another branch. Hanging branches are a repeat of the upper branch, and receive minimum light
Remove branches or part of branches that are duplicating another. As with the hanging branches, shaded ones do not receive enough sunlight to grow well and produce good fruit.
Cut back the top branches until they are slightly shorter than the ones below it. Continue doing this until the tree is a pyramid shape. The sun reached all branches when a tree is pruned in this fashion.
Fruiting wood grows on branches that are over 2 years old. They are easily recognized as they are thicker and grow slower than other branches.
As the tree ages, remove older fruiting wood from the center of the tree and keep the new wood closer to the end of the branches where the apples will receive more sunlight and be easier to pick
To keep apple trees in top shape they should be pruned yearly.
Linda Tomlinson is a horticulturalist that lives near Rocky Mountain House. She can be reached at www.igardencanada.com or your_garden@hotmail.com