Deeper isn’t always better when transplanting trees
- Published: Tuesday, Apr. 14, 2009
COLUMBIA, Mo. – You don’t have to break your back when transplanting a tree, said a University of Missouri horticulturist.
Research on tree root growth after transplanting suggests that you do not have to dig a deep hole, said Chris Starbuck.
“In most soils, 90 percent of the actively absorbing root tips are within 12 inches of the soil surface, so it’s important to create a soil environment surrounding a new tree in which roots can grow easily near the surface,” he said.
Plant trees no deeper than they grew in the nursery into soil that has been loosened 8 to 12 inches deep over an area two to three times the diameter of the tree’s soil ball, he said.
Place excavated soil on a tarp to make it easier to return soil to the hole after the tree is in place. Dig the hole only as deep as the soil ball and place the ball on undisturbed soil. If the soil is heavy clay, plant slightly higher than the tree was grown in the nursery.
Backfill so that the ball is about half-exposed and stable. Remove any twine or rope around the trunk. Many tree planters put water in the hole at this point to settle the soil.
If the ball is being planted high and the top will project out of the ground, remove the burlap from the top of the ball to prevent wicking of water from the ball where the burlap is exposed. Finally, finish placing backfill soil around the ball and tamp gently.
Roots of turf grasses compete with tree roots for water and minerals, so it is important to mulch a new tree as soon as possible. Mulch should be no deeper than 2 to 3 inches, tapering to less than an inch next to the trunk.
Until the roots grow out into the surrounding soil, the tree depends entirely on water contained in the ball. Trees with soil balls need frequent watering with relatively small amounts of water for the first season after planting.
For a simple form of drip irrigation, use a plastic 5-gallon bucket with small holes drilled in the side to let water trickle slowly into the root ball. Repeat this two to three times a week to keep the ball moist without drowning the tree.
Be careful not to overfertilize a new tree. A soil test prior to planting will point out any deficiencies in phosphorous and potassium. Corrections can then be made while replacing backfill soil.
Excessive nitrogen fertilization at planting time can promote top growth at the expense of root growth.
For more information, see the MU Extension guide “How to Plant a Tree” (G6850), available for purchase or free download at www.extension.missouri.edu/explore/agguides/hort/g06850.htm.
Soil testing is available through MU Extension’s Soil and Plant Testing Laboratory. For more information, see soilplantlab.missouri.edu/soil/, call 573-882-0623, or contact your local MU Extension center.
Writer: Robert Thomas
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