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May 2000 |
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Newly Planted Trees, Shrubs Need Extra Water to Avoid Drought Stress |
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Avoid Drought Stress Jim Jarman
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Even established plants have been showing signs of our short soil water supplies. So, with a dry spring and predictions of a summer drought, it is even more important to take steps to protect newly planted trees and shrubs. Most trees and shrubs can not be considered established for two growing seasons after they are planted. Until they are established, watering is a tricky problem. Roots from balled and burlaped or container plants may not grow out of the soil ball into surrounding soil for several months after planting. The plant must depend on moisture in the original soil ball to sustain it. Water from surrounding soil generally will not move into the soil ball. So you have to supply the soil ball frequently with small amounts of water. If possible, remove the "burlap" or other natural material from the outer ball. Otherwise, make some slits or cuts in the balling materials. You must remove any synthetic materials, containers, ropes, twine, and wire. These materials will not break down and will eventually strangle the tree or shrub. On a windy, 95-degree July day, a transplanted two-inch red maple may transpire two to three gallons of water. A tree like this may suffer severe drought stress in just a few days. The challenge is to replenish the moisture in the soil ball without leaving it saturated for an extended period. Drip irrigation that wets the ball itself is the best approach to watering a tree for the first year after planting. This is better than watering by hand using a hose or allowing a hose to trickle at the base of tree for some period of time. The person watering usually has no idea how much water has been applied and there is no guarantee that the water actually went to the soil ball. Much of the water could run off or the soil ball may stay saturated for days. Saturated soil, water logging, during a period of high temperature can cause as much stress as drought. Tree roots need air as much as moisture to support tree growth and moisture uptake. The air is forced out of the soil by the water in water logged soils causing root death. Some trees are much more sensitive to water logged conditions than others. A simple drip irrigator can be made by poking a few small nail holes in the sides near the bottom of a five-gallon bucket placed next to the tree and fill it with water every few days. Or, in a more sophisticated approach, insert two or three one-gallon-per-hour drip emitters into a short length of plastic tubing that can be attached to the end of a hose. This can be attached to an inexpensive battery operated timer set to turn off the water after one or two hours of operation. Many nurseries, garden stores or mail order houses sell drip irrigation kits that can be used for this purpose. Mechanical timers that run by water pressure are not designed for drip irrigation. Information for this article comes from Chris Starbuck, Extension Associate Professor of Horticulture at the University of Missouri - Columbia, (573) 882-9630.
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