Watering Newly Planted trees Until Establishment

Newly planted trees need supplemental watering to get established

Lisa Klein: Ask a Master Gardener

July 26, 2015 12:00 am

Q: I planted some maples recently and am unsure as to how much water they need and how long I should be watering them. Suggestions? Roland, Tulsa

A: Supplemental watering is often neglected after planting a tree, which is one of the major causes of loss of young trees along with incorrect planting.

At a recent OSU horticultural conference, urban forester Chris Martin suggested a scientific approach to irrigation of newly planted trees. He stressed that these recommendations should be modified according to temperatures and the amount of rainfall.

For best establishment and in the absence of rain, a newly planted tree should be shallowly watered daily for two weeks and then should be watered deeply three times weekly. As to how long to water, he suggested seven months of watering three times per week for each inch of trunk diameter. So if a tree is 2 inches in diameter, water three times a week for 14 months. This is about the amount of time it takes for most newly planted trees to grow enough roots to be considered established.

Newly established trees and mature trees need to be watered deeply once per week, depending on the amount of rainfall. The recommendation for the amount of water to be applied to newly planted trees at each irrigation is also based on tree size. These trees should receive 5 gallons of water per inch of trunk diameter at each application. A tree 2 inches in diameter should receive 10 gallons of water at each watering. To be more accurate, he also suggested using a soil moisture probe to determine when and if the tree needs water. In the absence of a probe, consider using the above formulas.

Other recommendations for young tree care include tree wraps and mulch. Tree wraps should be applied to the trunks of thin-barked trees such as maples in October and removed in March. These crinkled Kraft paper wraps are widely available in garden centers. Wraps prevent freezing and thawing damage to newly planted tree trunks. This is the major cause of split bark and large open gaps in trunks of young maple and other trees. This damage definitely shortens their life span. These wraps are not needed in summer and may be harmful by providing a home to damaging insects and disease.

All trees should be mulched after planting. Two to 4 inches of a loose mulch will conserve water, moderate ground temperatures and keep out weeds and lawn equipment. Keep the mulch a few inches away from the trunk. If piled up on the trunk, it promotes disease and pest problems. It has been shown that all trees mulched after planting grow much faster than unmulched ones.

For more information about tree care, go to tulsamastergardeners.org and review tree planting and care information under “Lawn and Garden Help.”

Garden tips

Garden tips

Spider mites are a difficult pest to deal with. They love hot, dry and dusty weather. Tomatoes are a favorite target where they cause a stippling or sand-blasted appearance. They are very small but may be seen if you tap a leaf over a sheet of white paper and look for moving dots. Treat with jets of water to wash them off and use either horticultural soap or oil according to directions. Neem oil is a good choice for a safe organic insecticide. If you use an insecticide of any sort, it is best to spray very early or late in the day when honeybees are in their hive.

Tomato growers are aware that fruit production usually stops in the heat of summer. Most tomato pollen becomes infertile and blossoms drop off when night temperatures are above 70 degrees and daytime is above 92 degrees for a few days. This also occurs in peppers, some varieties of beans and other vegetables. As it cools in late summer, fertility returns. If your tomatoes are too tall and gangly, you may cut them back a third. New growth and fertile blossoms will develop when it cools in fall.