Take Care With Roots When Planting Tree From Container

Q: What's the best way to plant a tree grown or sold in a container?

A: Both the tree and the planting spot need to be carefully chosen to prevent future problems, including blow down. Select a planting location with good drainage; root rots are common problems in Western Washington. If the area shows standing water in winter, most trees will not thrive. Oxygen is essential to plant's health and poorly-drained soils lack this necessary element.

Several myths persist about planting practices. Trees have been shown by research to establish and grow best when they are planted in unaltered native soils. You need to avoid the impulse to add a lot of extra peat moss, compost, leaf mold, sawdust or other amendments to the hole to "improve it" for the tree. These additions cause roots to stay bunched inside the hole in the "good" soil thus not growing broadly away from the trunk. The result is a tree that has a small, confined root system that will be out of proportion to the tree as it grows taller and branches out.

The mistake of amending soil as you plant creates a kind of "tub" inside the hole that may also contribute to poor drainage and root rots.

-- Thus, the first rule is to plant the tree in unaltered native soils with good drainage.

-- Secondly, dig the hole deep enough so the bottom of the root ball rests on the bottom of the hole and the top of the root mass is at the soil line. Dig a hole wider than the root ball, not

deeper. Make the hole at least twice as wide as the root ball.

Research on tree growth has shown that root systems are the most dense in the top 12 to 18 inches of soil where air is most available; tree roots will grow out as a big flat pancake, not as a "carrot" shaped deep pronged root that many people suppose supports big trees. You want to prepare the ground to offer hospitality to exploring roots as they grow out into the surrounding soil.

-- Look at the plant as you extract it from the container.

Are roots heavily wound around each other, circling the interior dimensions of the container? If so, they're called "girdling roots" and they will, if left untouched, continue to circle the plant, never growing out to offer support. They may even eventually strangle the plant. Cut off any dead (brown and rotted) roots, and cut and release the circling roots to spread them so they will expand away from the original container shape and properly support your plant.

Containers can hold surprises. Sometimes a pot will contain a plant that is wrapped in burlap, then surrounded by soil. Or you may buy a ball-and-burlapped plant. You may then find that the plant was grown in a heavy clay or in a soil that is considerably different from the soil in which you are to plant.

-- If so, gently wash or pry away enough of the original planting medium to expose the roots to their new soil home. The root must make contact with the soil to grow properly.

-- Remove any synthetic burlap or wrappings and pins before planting. If the tree is wrapped in natural burlap the material will eventually decay but be sure no tag ends of natural burlap remain above the soil line to wick water out of the soil and damage the plant's health.

-- Fill in carefully, working soil gently in with your hands or a tool to avoid air pockets. Don't do a stomping dance on top of the root ball.

-- Water immediately upon planting, being sure that the top of the root ball is not deeper than the soil line.

-- Add a few inches of an organic mulch such as sawdust on top of the soil.

-- Call 296-3425 to hear Tape No. 1661 "Planting Container-Grown Shrubs." Gardening runs Friday in Scene and Sunday in Home/Real Estate. It is prepared by Mary Robson, Master Gardener program director, Holly Kennell, Washington State University/King County Cooperative Extension agent, Susan Miller, integrated pest management specialist, and volunteer Master Gardeners.