Oregon State University’s Former Horticulturist Suggests About Paying Attention To Trees During This Time Of Year

It’s the time of year when fruit trees are on the minds of beginning and experienced backyard enthusiasts. More and more homeowners are adding fruit trees to their landscape and now’s the time to buy, plant, prune and spray.

Whether you have one or several, or plan to plant your first fruit tree, it’s time to give them the attention needed to keep them healthy and bearing fruit. Nurseries have them in stock and can help you make decisions. Best to buy disease-resistant varieties to avoid the pest and disease problems that plague fruit trees.

“If you start from that point, you’ve got a much better chance of having a low-input orchard,” said Steve Renquist, retired Oregon State University Extension Service horticulturist. “You don’t have to be constantly spraying for something.”

If you have a small space for a tree, purchase a tree on dwarf rootstock, which takes up less space and stays short enough to make picking fruit easier. Give dwarf trees at least 5 feet of space between other trees to maintain some vigor and health.

To help guide you, whether you are experienced or a beginner, Renquist offers these tips:

Pruning

Perhaps the most mysterious and asked-about part of owning a fruit tree is when and how to prune it. Now’s the time. Trees left unpruned are more susceptible to pests and diseases and produce less fruit. To get detailed instructions, refer to “Pruning Fruit Trees,” a 10-Minute University video created by OSU Extension Master Gardeners. Another good Extension resource is the publication “Training and Pruning Your Home Orchard” and the article “How to restore old fruit trees” has step-by-step directions for pruning overgrown trees.

Planting

Fruit trees can grow well in a variety of soil types as long as the soil is well-drained. If you are growing standard-size fruit trees, you should have soil that is 4 to 9 feet deep. Soil that is 3 to 5 feet deep is sufficient for growing fruit trees on dwarfing rootstocks.

If your soil is compacted and shallow, you may decide to make raised beds. For dwarf fruit trees you will need at least 2 feet of raised bed on top of a foot or two of soil.

When planting a tree in the ground, do not add a large amount of purchased topsoil or compost to the hole to improve the soil. A little compost mixed with the native soil will be sufficient. The tree’s roots will not leave the planting hole if the modified soil is much lighter than the native soil. To learn more about how to plant a tree, see Extension’s “Selecting, Planting and Caring for a New Tree.”

Fertilizing

Don’t put any nitrogen fertilizer in the planting hole. During the first year, allow the tree to grow for several months before applying nitrogen to the surface of the soil. This will keep you from burning the young tender roots.

Eventually, you can apply three-quarter cup urea (46-0-0), or 1 3/4 cup of ammonium sulfate (21-0-0) to each tree. Adding 5-10 pounds of aged manure or compost per tree is also a good idea. Fresh manure will burn roots of your new tree.

Generally, it’s a good practice to spread fertilizer at the drip line of the tree. Remember to water in the fertilizer.

Watering

Only plant fruit trees where you have a water source for irrigation during the dry summer. Fruit trees, especially during the first four to five years, require watering to make good growth. When watering fruit trees, you should give them a deep soak that will penetrate several feet into the soil.

Spraying

Renquist’s recommendations for sprays are for low-impact sprays, many of them organic, though he points out that even some organic products have risks. A good reference for disease and pest control is Extension’s “Managing Diseases and Insects in Home Orchards,” which has a list of cultural practices and least toxic products for various pests and diseases. For information on specific products on the list contact your local Master Gardener Program.

Renquist stresses that home gardeners need to rotate sprays – three per season is best – to avoid building up resistance to sprays. For instance, if your apple, pear or plum tree has coddling moth, he recommends Cyd-X, a virus that is non-toxic to anything but the moth; the organic form of spinosad; and Surround, which is a kaolin clay compound that irritates the moths and keeps them away.

Another strategy, Renquist said is to apply low-input dormant oils during the dormant season (now) before trees have budded out. The oils smother the eggs and larvae of many insects and decrease problems down the line. Of course, keeping your trees in top shape is key. Get more tips in “Get a leg up on fruit tree problems with dormant oils.”