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Margaret Lauterbach: Proper pruning encourages healthy growth in the garden

Experienced gardeners know that pruning trees stimulates growth below the cut. It also stimulates bushiness on herbaceous (non-woody) plants such as squash vines and basil. Squash vines won’t turn into bushes, but they’ll send out new lateral branches with female blossoms if you nip off the end of the vine. Some vines really go wild, so it’s good to trim them back a bit.

If your vines are sweet potato vines, you can eat the leaves. The leaves are about as nutritious as the tubers, and as nutritious as spinach without the oxalic acid taste. This would work as a summer spinach, providing you’re not counting too on an abundant harvest of tubers, for the leaves’ conversion of water, sunlight and carbon dioxide into sugars to feed the plant is the action that creates the tubers we love. Common spinach doesn’t tolerate hot weather.

We usually prune trees and shrubs in winter, when they are dormant. That pruning has a delayed stimulating effect on growth, sometimes resulting in watersprouts or other unwanted growth. Summer pruning is a little more difficult, because you can’t see what you’re doing as well as you could after leaves drop, but summer pruning does not result in as vigorous new growth as the winter pruning does. Worst times to prune trees are when they’re developing leaves or losing leaves.

Some of us also delay pruning “bleeder” trees until summer, even though the running sap is not a dangerous loss for the tree. It does create a mess. Bleeder trees include maple, birch, magnolia, elm, walnut, willow, sumac, honey locust, black locust, European hornbeam, poplar, walnut and dogwood. Grape vines, too, freely bleed sap if they’re pruned later than February in this area. If you’ve pruned and sap is running, leave it alone to air dry. Don’t try to stem the flow.

Most ornamental trees usually don’t need pruning, but occasionally you need to prune to shape or to keep a sidewalk free, for instance. Dead, damaged or diseased wood should be removed, of course. This is a good time, too, to remove watersprouts (branches or twigs rising vertically from fruiting branches) from fruit trees.

Save your true potato seed

In the vegetable garden, keep your eyes sharp for marble-sized fruits on your potato vines. They’ll appear at the upper tips, where flowers have been. Harvest those little fruits and set them aside to mature and await planting in spring, for they’re little bundles of true potato seed. Some potato varieties set a lot of seed pods; others set few or none. If you have extra garden space, next spring plant those seeds. They’ll form plants and small tubers that you can plant the following growing year. If they’ve not been cross-pollinated by another variety of potato, you’ll get more of the variety you harvested the seed from.

One of the main benefits of planting from true potato seed is that it is naturally disease-free. Seed potatoes are not necessarily disease free.

Combat earwigs

Some are reporting significant damage from earwigs feeding on garden plants. Diatomaceous earth is an organic control that works on earwigs, but if you use it, apply it to foliage, not blossoms, after honeybees have retired for the night. Rain or sprinkling will wash it off your plants, but if neither event occurs, the diatomaceous earth will just lie in wait to puncture the bodies of insects.

A threat to grape vines

Watch grape vines for invasions of mealybugs. These are scale insects that as adults are coated in a white waxy or cottony cover. They suck plant juices, and in large numbers they do a lot of damage. Researchers are finding them in test plots near vineyards in our area.

Did your grape vines bear this year? I have a vine of the late Ross Hadfield’s red Himrod that usually bears delicious grapes, but after severe February pruning, it’s burst forth with extensive vines and leaves so lush we can’t find grapes or blossom residue. I suspect it didn’t produce fruit this year at all.

Send garden questions to melauter@earthlink.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.