March 13, 2011

Maine Gardener: The ‘hole’ truth about planting trees and shrubs

By Tom Atwell
Staff Writer

Planting a tree or a shrub in your yard should be easy. You dig a hole in the ground, put the plant in the hole, put the soil back in the hole, water it and then walk away.

And while all of this is accurate, it does leave out some information. How deep should you dig the hole? How wide? What should you do to the plant's roots? Should you add anything to the soil? Do you stake the plant?

Back in January Jeff O'Donal gathered a group of landscape professionals at his Gorham nursery to discuss the proper planting techniques for woodies -- landscaper jargon for trees and shrubs. Not all of the professionals agreed on everything, but O'Donal got them to agree on the basics.

Woodies you buy from a nursery will be balled and burlapped -- with the roots contained in a wire basket and then wrapped in burlap -- or in a container, basically a plastic pot. You also can buy bare-root plants, mostly from mail-order companies. This column will cover balled-and-burlapped plants first, with a description of pots and bare-root plants at the end.

Balled-and-burlapped plants usually have been grown in a field and dug out before being shipped to the nursery.

"As much as 80 percent of the plant's roots stay in the ground," O'Donal told the landscapers, displaying a picture of a tree root system extending well beyond the outside edge of its leaf canopy. "Only 20 percent goes with the tree. People are really purchasing a partially rooted giant cutting."

The first thing a gardener needs to do before planting the tree is to measure the height and width of the root ball. The next step is to open the burlap and find the root flare, also called the trunk flare. This is an area where the trunk widens out close to the roots. Many times, for many reasons, the soil in the root ball will be several inches above the root flare. Remove all of this excess soil above the flare.

The hole for the plant should be dug deeply enough so the root flare will be barely above ground level and the roots are below ground level while the root ball is resting on solid, undisturbed soil. The hole should be three times the width of the root ball, so you have loose, fertile soil into which the roots can grow.

Lifting by the intact wire basket, place the root ball in the center of the hole. Make sure the depth is correct so the root flare will be visible when the project is done but the roots will be completely covered, and then turn the plant so it is facing in the direction the decision-maker in the home wants (read: wife).

This is where the landscaper disagreement begins. O'Donal recommends filling half the hole with soil taken from the hole and amended with compost or other organic matter and mycorrizae, a fungus that helps plant roots absorb nutrients.

Others say that you should then remove the wire basket and burlap before adding any soil.

O'Donal said that 90 percent of a plant's roots are within a foot of the ground surface, so you have to remove only the top half of the basket and can do that once some soil has been returned to the ground. Some of the landscapers said they have removed too many dead trees with the roots trapped in the basket, so they want to remove all of the basket, if possible. Some landscapers don't even want to leave burlap in the hole because, though it looks organic, some burlap is polyester.

(Continued on page 2)

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