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Archive for Thursday, August 14, 2008

Trees, shrubs struggle to establish

August 14, 2008

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This is crunch time, the heat of summer, the days when young trees and shrubs choose to live or die. This is the time when what we have done, or have not done, really makes the difference.

Here are the top reasons why trees and shrubs fail to establish after planting:

¢ String trimmer and lawnmower injury to trunk. That little chunk of bark is really important. Right underneath the bark is the only living part of the tree, and most likely a chunk of that was removed with the bark. The only thing worse is to let the tree scar over the wound and hit it again.

¢ Improper planting depth. The mulch around the base of the tree should be in doughnut shape - not a volcano. Mulch holds moisture against the trunk of the tree, making it a prime location for decay. Even worse, roots may grow upward and girdle the trunk. When planting, remove soil from the base of the tree until you find the place where the trunk begins to flare. You can also look for the first major horizontal root. The flare or root should be at ground level or slightly higher.

¢ Improper watering. Water trees and shrubs deeply and infrequently. Instead of holding the hose over the plant for five minutes every night, turn the pressure down to a trickle and let the water run out slowly for a long period of time. Slope, soil type and mulch influence the amount of time you can let the water run before it starts to run off. Avoid overwatering in irrigated lawns. In clay soils, too much water leaves the tree sitting in a bowl of water.

¢ Competition with turf. Letting the lawn grow right up to the trunk means that roots of the grass are competing with the roots of the tree for water and nutrients. Guess who usually wins? Grass. Mulch (properly, in a doughnut shape) to reduce competition.

¢ Sun/shade requirements. Pay attention to how much light different parts of the yard receive. The bed on the north side of my house receives far more sunlight than the bed on the south side of my house and is planted accordingly. Many trees and shrubs require full sun to thrive; if you have shade, look for plants that can tolerate low light.

¢ Plant selection. Sure, it looks pretty at the garden center, but can you maintain the level of care it is receiving there? We are in USDA Hardiness Zone 5, although we are on the margin for Zone 6. Lower zone numbers are colder climates. If you select a plant that is listed for Zone 3, it may struggle in the summer heat. Zone 7 plants are unlikely to survive the winter here.

¢ Soil pH problems. Azaleas need acidic soil with a pH of 4.5-5.5. Soil pH in Douglas County is often 7.0 or above, although levels are widely variable. Test your soil if you want to plant something that prefers acidity.

¢ Poor timing of planting. You can get some great deals at the end of the season, but if you plant a tree in July, expect to spend even more time babying it along.

¢ Lack of continued maintenance. Just because the yews made it through the first season, they still need some care. Many people care for new plantings the first year, then leave the plants on their own. Keep watering, mulching, etc., as needed, preferably for the life of the plant. As plantings mature, reduce frequency of watering - but even large, old trees and shrubs need supplemental water during dry weather.

¢ Insects and disease. This is last on the list for a reason - it is the least likely cause of young tree and shrub death. The best control is to keep a close eye on your plants and identify the problem early. Bagworms have been feeding since the middle of May, but they are just now noticeable. By now, they have done most of their damage. Catch it early next time.

Have gardening questions? Call the Douglas County Extension Master Gardener hot line at 843-7058 or e-mail dgemg@sunflower.com.

- Jennifer Smith is the Douglas County Extension Agent-Horticulture for K-State Research and Extension.

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