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Treasure Valley gardening questions answered


In the e-mail bag this week we find two very timely questions pertaining to two very different kinds of trees.

Jean B. of Meridian asks: "What's wrong with all the elms around the valley? They're all brown."

Jean, the elms are covered right now with billions of dried, round, wafer thin seeds which give them that tan color you're seeing. Once those little seeds drop, the leaves will begin showing up and the trees will have their green coats once more.

Siberian elms rank right up there with cottonwoods when it comes to being prodigious seed producers. And believe me, darn near every one of those little paper coated embryos will sprout wherever they happen to land ... in the flower bed, in the lawn, in the dirt driveway, in the horse arena, in the pasture, under the deck, in a crack in the sidewalk ... I've even found them growing in potted plants crowding out the rightful plant resident. One industrious elm seedling had grown into a 7-foot-tall tree unhampered by the 4-inch plastic pot that it was in. It managed to send a root out the drain hole in the bottom of the pot and was well on its way to becoming a full fledged tree before I interrupted its growth cycle by pulling it up to take as a "show and tell" to my horticulture class. Its persistence under adverse conditions was admirable and it got a good laugh from the students who thought it was funny to see so large a tree growing in so small a pot.

The Siberian elm is very drought tolerant. It can grow with hardly any water in the worst of soils. Any tree that can do that, plus provide an abundance of shade, is worth its salt in this arid region. It's often called a "trash tree" because it drops lots of seeds and branches—both big and small. Siberian elms have a propensity for forming narrow crotch angles where their branches connect, thus causing branch attachments to be weak and prone to easy breakage.

Claude T. of Boise writes: "Each year I spray my apples at the beginning of the season for insects but at harvest time I still have wormy apples. What am I doing wrong?"

The critter that's causing the worms in your apples, Claude, is the codling moth.

The destructive little larva of this moth is considered one of the worst apple pests and is responsible for thousands of hours of labor and large amounts of pesticide use in orchards today. The moths also lay eggs on pears as well. These fly-by-night critters as adults are gray brown, with pale, fringed hind wings and a wingspan measuring up to three-fourths of an inch. They are attracted to black light bug zappers and can also be trapped with this special solution: Mix 2 cups water, 2 cups apple cider vinegar and 2 tablespoons of black strap molasses. Pour it into a plastic gallon milk jug. Cut two large holes on either side of the jug to allow the moths easy access to the tasty yuck inside. Hang the milk jug on an inside branch—one jug for a small to medium sized tree, two or three jugs for a large tree. The solution will need to be added to as it evaporates and changed regularly as it fills up with insects.

Another approach to wormless apples is to wrap the apples individually to keep the insects off the fruit. I knew a lady, Mary, who one year wrapped a hundred of her apples in bags that she sewed using support panty hose (nylons are too thin) and gym socks. She had her family help her tie the protective gear onto the tiny apples as a birthday gift. The bags were made big enough to accommodate the mature apple, plus she knew the material would stretch. Mary claimed the tree was such an attraction to anyone driving past that she had plenty of visitors stopping to ask what she was doing. Since she had pulled most of the other apples off the tree, the tree's energy went into making 100 huge apples.

To let the apples color up, the cloth baggies have to be removed a few weeks before harvest, otherwise the apples will be pale in color. It was a grand experiment that really worked, but when asked if she planned to do the bag trick again the following year, Mary said, "No, it was too much trouble."

Most folks choose the conventional method of controlling codling moths; they spray their trees with insecticides like Sevin about every seven to 10 days starting around May 20 and continuing throughout the growing season. You may not be spraying your trees enough, Claude, the codling moth has more than one generation in a season. That's why so many spray applications are needed. The leaves don't need to be sprayed, just the fruit. It's definitely a hassle to get tree-ripened fruit without worms, that's why most people let the orchardists do the work for them and buy their apples.

Suzann Bell is a horticulturist with the University of Idaho Extension in Ada County. Send gardening questions to Suzann at: