Question: We have some badly neglected apple and pear trees in our backyard. They have become so large and overgrown that although they provide wonderful shade, they produce very poor quality fruit and very little of it. What should we do?

Answer: A good fruit tree should not be a good shade tree. However, when pruning is neglected, many apples and pears become better shade producers than fruit producers. Standard sized trees often outgrow the reach of ladders and pole-type pruning saws. It is with good reason that home gardeners prefer dwarf or semi-dwarf trees which are not as tall and are easier to prune, spray, and harvest without the use of ladders.

A neglected but otherwise healthy tree will usually show a marked improvement in fruit quality as a result of pruning. Fruit buds begin developing in the growing season previous to the one in which they mature into fruit, and more are initiated than can be fully developed into fruit. Growing conditions during the season of bud initiation and the subsequent winter will affect the number of buds which flower. In addition, certain cultivars are "alternate bearers" that seldom initiate many buds during a year with a heavy fruit crop. By late winter the buds for the coming summer's crop will be very evident. Buds only appear on two or three year-old twigs or spurs which are no thicker than a pencil.

The primary purpose of pruning is to increase sunlight penetration, remove less productive wood, and shape the crown into an efficient, stable form. If left un-pruned, the quantity of fruit produced might be greater, but the quality much lower. Pruning increases fruit size, promotes uniform ripening, increases sugar content, and decreases insect and disease problems by allowing better spray coverage and faster drying after rainfall. It also allows easier access for timely harvesting.

Unfortunately, backyard trees are sometimes over-pruned when the owner tries to remove too much wood all at once in order to drastically reduce the size of a tree. "Topping" or shearing a fruit tree is about the worst thing that can be done! Ultimately, both shearing and topping will produce a dense crown that inhibits access for sunlight, sprays and harvest and invites weak structure and limb breakage.

WSU Extension has a couple of excellent resources available to help guide you through the pruning process. They include Pacific Northwest Bulletin Number 0400 titled: "Training and Pruning Your Home Orchard," which is available for $2.50 and "Pruning Apple Trees- Basic Concepts," a 24 -minute video, is available at a cost of $15. Both can be ordered through the Publications office at Washington State University by dialing (800) 723-1763 or online orders can be made at (

Question: Yikes! We just found a bunch of little caterpillars in our Douglas fir tree. What are they? Will they crawl onto other plants and eat the leaves?

Answer: More than likely, the caterpillars you re describing are the larvae of the Silver-spotted Tiger Moths. The main host for this pest is Douglas Fir, but it sometimes feeds on spruce,, pine and other conifers. The chewing damage caused by the silver spotted tiger moth larvae is limited and usually not very serious. Home gardeners who discover this pest can prevent additional feeding damage by simply pruning out the infested branch and destroying the insects. They are not known to feed on garden plants other than those listed above.

Question: We have the opportunity to get a load of sawdust at minimal cost. Would it be okay to incorporate it into area where we intend to plant our vegetable garden this spring?

Answer: Sawdust is often readily available, but is the least desirable source of organic matter. Sawdust ties up nitrogen as it decomposes in the soil causing plants to suffer from nitrogen deficiency. The nitrogen deficiency from sawdust decomposition often lasts 2-4 years requiring additional applications of nitrogen to supply plant needs. If you do decide to add sawdust, make sure you add nitrogen in doses of 1 pound per 1,000 square feet of garden as needed. Nitrogen deficiency (pale green leaves and slow growth) is usually most apparent during the summer when sawdust decomposition is fastest and plant demand for nitrogen is greatest.

EDITOR'S NOTE: For answers to local gardening questions, contact Master Gardener Rachel Gana at 642-8723 or e-mail her at:

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