Extension Educator, Horticulture
A warm spell in February equals a warm handled pruning saw. Generally pruning is best done when trees are dormant. If you are dying to prune, few trees need as much yearly pruning as apple trees. Left to wander wildly apple trees can get too tall for easy harvest, may bear fruit only at the tops of the trees and may produce many apples but fruit will be small and misshapen. Apple trees may also show biennial bearing in which fruit is produced every other year. Apple trees that have not been pruned for several years pose challenges.
Most apple trees planted years ago, before the semi-dwarf or dwarfing roots were available, were standard (full size) trees grafted onto seedling rootstocks. These types of trees tend to grow taller and have longer branches leading to shading of many shoots, particularly the lower branches. However even semi-dwarf trees can grow well out of our reach if left unattended.
With unpruned apple trees larger fruits are borne mainly on the top part of the tree that receives sunlight. Smaller, misshapen fruits are borne in the shaded parts of the tree. Misshapen fruits may also be due to disease and insect pest damage. In order to rejuvenate these trees and increase fruit production, they need to be pruned so that all the branches and shoots receive good sunlight and proper spray coverage. Old adage is the tree branches should be far enough a part that you could throw a football through the tree.
A pruned tree will have good sunlight exposure to all the branches, will be of a harvestable size, have branches with wide crotch angles that support fruit load, allow good spray coverage to all shoots, and bear good-quality fruit every year.
Pruning is done between February 1 and April 1. Pruning can be done with simple tools such as hand pruners for small shoots and spurs. Larger shoots can be removed using lopping shears or a pruning saw.
Pruning neglected trees is done more severely, than annual pruning. Generally apples bear fruit on spurs, shortened compressed stems, that arise from branches that are more than one year old. The first step in pruning neglected apple trees is to remove any dead, diseased shoots or branches. Be sure to sterilize tools with bleach or bactericidal spray between each cut if disease is suspected.
The second step is to prune upward-growing shoots (water sprouts) and downward-growing shoots. The strongest branches are horizontally growing. The third step is to prune shoots and branches that are crossing other branches and any branches that shade other branches.
The final step is to prune shoots that grow from the base of the tree trunk called suckers as these are areas where damaging insects may hide. Once the tree is rejuvenated, moderate pruning should be done annually during the dormant season.
Do not leave any branch stubs. Also thinning cuts (removal of entire branch) are better than heading back cuts. Heading back (removal of branch tips) produces a proliferation of unwanted stems at the branch ends.
The downside to performing a lot of pruning in one year is that severe pruning leads to more water sprouts and suckers. The better method to rejuvenate mature, over grown trees is with a three year process. Plan on removing some larger branches over a couple years rather than all in one season. With pruning mature apple trees just go for it or decide to prune at ground level and plant a new tree. For more information about apple trees visit http://urbanext.illinois.edu/apples/
Join us for Vermilion County Master Gardener Garden Day, March 9 in Danville. Shop and learn about trees, starting seedlings indoors and insect forecast for 2013. Register online http://web.extension.illinois.edu/cfiv/ or call 217-442-8615.