How to care for newly planted trees into fall & winter

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Last Updated: 
August 31, 2005

REDMOND - Have you planted any new trees in the last three years? Water, mulch and fertilizer are important ingredients for caring for younger trees. And don't forget to keep up care into fall and winter.

Newly planted trees require routine and thorough watering regularly for at least three years after planting, says Stephen Fitzgerald, forestry specialist with the Oregon State University Extension Service.

Soil and weather conditions, as well as the amount of competing grass around the tree, dictate how much water to give your new tree and how often.

"In general, trees need the equivalent of one inch of rainfall per week from June through September," said Fitzgerald.

Trees use water even during winter. Just before the ground freezes in late fall, give your tree a thorough watering. During mild winters, where temperatures are above normal and the ground thaws, give your tree periodic watering. This is particularly important for conifers, which retain their needles and use water readily during winter.

Before you water, examine the soil moisture four to eight inches deep. If the soil feels dry or just slightly damp, it needs water. Well-drained, sandy soils will need more water more often than a loam or clay soil. The best way to water a newly planted tree is to place a garden hose at the base of the tree. Run a slow trickle of water for several hours or until the soil is thoroughly soaked. To help hold or direct the water around the root system, build a temporary soil berm or saucer. Avoid short, frequent watering, which promotes development of a shallow root system that is more vulnerable to drying out and other stresses.

In eastern Oregon, plant ornamental and shade trees in an irrigated landscape or hand-water them regularly to ensure their survival. In drier regions of eastern Oregon, trees often need water during winter to prevent desiccation.

Mulching around the base of the tree is an important part of long-term tree care. A mulch keeps the soil moist, limits weed growth, and discourages injury from lawnmowers and weed-eaters.

Wood and bark chips are good mulching materials. You can use a porous landscape fabric as a weed barrier underneath the chips, but don't use plastic because it suffocates the roots. Apply a three- to six-inch layer of mulch and spread it to form a circle at least three feet away from the trunk. Keep the mulch from direct contact with the tree trunk. Some bark mulches may contain pathogens or contaminants that can harm your new tree. Maintain the mulch ring to keep grasses from competing with the tree.

Generally, you don't need to stake trees, says Fitzgerald.

"Young trees standing alone with their tops free to move will develop stronger, more resilient trunks than tightly staked trees," he said.

However, too much wind can bend young trees and disturb the root ball, damaging roots and stressing the new tree. Staking helps trees that are top-heavy and would lean without additional support. Staking also helps protect trees from vandalism and mechanical damage.

In areas of Oregon exposed to high winds, such as the coastline, trees may need additional protection. Use temporary wind barriers made of plastic or cloth, but remove them within 1 year once the tree has developed a stronger root system.

To properly stake a tree, you need two wooden or metal posts. Drive them into the sides of the excavated planting hole before you backfill to prevent driving them through the root ball. Secure the tree to the stakes with broad straps or hose; don't use wire because it will girdle the bark of the tree. Guying and staking the tree will keep it secure from blowing over, but allow the trunk to move up to two inches in any direction.

If staking doesn't allow some movement of the tree's trunk, the tree will not allocate any growth (wood) to the main stem and it will be unstable when you remove the stakes and guying. Remember to remove the stake and guying materials within a year.

Autumn is also a good time to fertilize established trees (1 year after planting) every two or three years in the fall after the leaves have dropped. Or, fertilize in the early spring before growth begins. Apply the fertilizer directly to the soil surface and water it in. If there is thick grass sod beneath the tree, use a pipe to punch holes 12 inches deep in the sod beneath the drip line of the tree and apply the fertilizer in the holes. This helps the fertilizer reach the tree's root system. Avoid using "weed and feed" fertilizers around the root zone of your tree.

Don't apply nitrogen in late summer because it can stimulate new growth that may not "harden off" or go into fall dormancy properly and will be more easily damaged by early fall frosts.

Author: Carol Savonen