Articles by Jim Gainan

As published in the Billings Gazette

Gardening Today: Pruning Fruit Trees

Pruning Fruit Trees

Why Prune?

1. To remove dead or diseased wood.
2. To control the shape and strength of the tree.
3. To enhance fruit production.

When Should You Prune?
The best time to prune fruit trees in Montana is late winter or early spring before the blossoms open. This is also a good time to apply an application of dormant oil/lime sulphur to kill insect eggs and fungal spores. If you are pruning out dead or diseased wood, it is easy to spot by late winter because it appears shriveled and its buds are dried as compared to live wood with its healthy, swelling buds.


What Wood Should be Removed?

1. Water sprouts, which are overly-vigorous vertically growing branches and suckers, which grow vertically up from the base of the tree.

2. Small twigs, under 1/2 inch in diameter, which are growing toward the inside of the tree or from the underside of limbs. In general, you want to remove any fine wood which will not receive sufficient sunlight or which is blocking sunlight to the center of the tree.

3. Dead and diseased branches. Fruit trees which have experienced fire-blight in the past season will often exhibit evidence of this disease as dark, sunken lesions, called cankers, on the branches and twigs. These cankered areas should be pruned away from the tree at least 10 inches back from the edge of the lesion into healthy wood.

4. Cross-branches. Save the best of two branches that rub against each other.

5. Thin spurs. Apples bear most of their fruit on long-lived spurs-fat, stubby growth that grow less than an inch per year. As the tree ages the spurs become weak and over-crowded. Occasionally thin out old or over crowded spurs so that the remaining spurs are evenly distributed along the branch. (This applies to apple trees only).


What Tools Should be Used?
Depending on the size of branch you are pruning, cut only with sharp pruning shears, loppers, or pruning saw. If you are pruning a tree that is susceptible to fire-blight, sterilize your pruning tools after each cut with rubbing alcohol or a 10% solution of house-hold bleach.


Where Should Pruning Cuts Be Made?
Cut branches which are smaller than 1 1/2 inches in diameter with a pruning shear or lopper, cutting as close as possible to the origin of the branch. Never leave stubs, which will eventually die and may spread decay into the live wood. When cutting larger branches with a saw, follow the three steps illustrated in order to ensure that the bark on the trunk below the branch is not stripped off. Try not to cut into the "branch collar" on the trunk. The branch collar is a slight swelling around the base of the branch you are pruning off. The wound left after removal of the branch will heal much faster if the "branch collar" is not cut into.


How Do You Prune A Young Fruit Tree?
The main purpose of pruning a young fruit tree is to establish four or five strong "scaffold" branches which will form the framework of the tree. Choose these main scaffold branches carefully.

1. The ideal scaffold branch will extend from the tree trunk at a 45-degree angle.

2. Each branch should point in a different direction.

3. There should be intervals of at least 8 inches between scaffold branches.

4. The lowest scaffold branch should be at least 18 inches from the ground. When pruning the side branches which will emerge from the main scaffold branches, keep these points in mind:

* For the first few years, remember that your first goal in pruning is to let light into the tree from above so that more fruits will be produced and ripen well.
* The more vigorous a side branch is, the more it is cut back in order to keep all the branches in balance.
* Cut out branches that cross one another or grow right under the branch above.
* Regular maintenance pruning will also involve removal of any water sprouts or suckers.


How Do You Prune a Mature, Over-Grown Fruit Tree?
A fruit tree that has reached its mature size and is yielding fruit requires regular pruning. Often people "inherit" old neglected fruit trees which require some "reconstructive surgery". If the trunk is not hollow and most of the limbs are intact, they may be worth saving. The best way to tackle the job of restoring an old tree is in stages. 1. The first year remove any dead branches, suckers, and water sprouts. Try not to remove more than a quarter of the tree per year. 2. The second year remove the worst of the crossing or inward-facing branches. Also prune back or remove some of the top branches to let in light. 3. The third year repeat the last year's step, but do it more completely. Always remember to prune away no more than a quarter of the tee per year.