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Agriculture - Fruit tree winter pruning

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IN THE GARDEN by JENEEN WICHE/Garden Columnist

A healthy fruit crop from your favorite fruit tree can dramatically increase with some late winter attention.  Pruning is key to healthy fruit trees and fruit production.  You can prune any time after the threat of harsh winter weather is over until just before the tree is in full bloom.  Prune out any winter damage, branches that grow inward and crowded limbs.

Prune young trees (under five years old) by removing new or young shoots at their branch origin.  This thinning technique helps the young tree develop stronger primary branching and selected shoots, the skeleton of the tree, if you will.

For older trees, primary cuts should be made to thin the tree and allow light to penetrate the tree.  Remove limbs and branching all the way back to the collar for faster healing around the cut.  Have a diluted solution of household bleach nearby to dip your pruning tools in so that the potential of spreading a disease from one tree to another is eliminated.

If a fruit tree gets too bushy fruit development is compromised because not enough light reaches the interior of the tree.  Poor air circulation enables insects and disease to spread more rapidly.  

Fertilize your fruit trees in late February or early March.  You can take a soil sample now to determine the pH balance.  Different ratios are recommended for different types of fruit trees.  For instance, conventionally grown apple trees take 1/4 pound ammonium nitrate per year of age; pear trees take 1/8 pound per year of age, and cherries, peaches and plums take 1/5 pound per year of age.  However, never exceed more than three pounds of ammonium nitrate per tree.  Check the label for the correct ratio for your fruit variety.  When applying the fertilizer, sprinkle the granular around the drip line of the tree so that it can be absorbed by the feeder roots that are situated just under the end of the tree’s canopy. We prefer using organic materials for fertilization, so composted manure and cottonseed meal are used in our orchard.

Because insects love over-wintering, in fruit trees it is important to watch closely for your window of opportunity when it comes to applying dormant oil sprays.  Dormant oil is a light weight, high grade petroleum that, when sprayed on dormant trees with dormant insects inside, traps and smothers the unwelcomed guests.  Dormant oil is not effective during freezing weather and it can burn new growth...so timing is crucial.  Wait for a day where temperatures are above 40 degrees and remain so for at least 48 hours.  Do not apply the dormant spray if the tree has broken dormancy. I suspect we will need to pay close attention to the orchard this late winter and early spring because of the unusually mild weather we have been having.  It may be worth scouting the progress of bud break every few days this year!

The use of dormant oil is not reserved for fruit trees alone.  You can use it on other trees and woody ornamentals to control aphid eggs, certain mite eggs and scales.   Remember, the plant must be dormant.  It’s not called a dormant oil spray for nothing.

Of course, your best defense against managing pest and disease problems on fruit trees is planting disease resistant varieties to begin with.  Liberty, Jonafree and Sir Prize are some disease resistant apples that benefit from a treatment of the organic dormant oil spray and nothing else!   I like an apple I can eat directly off the tree.