Myth: You should add an amendment -- organic matter such as peat moss, compost or perlite -- to improve a single planting hole when you put in a new tree or shrub, especially if you encounter poor soil.

Fact: We don't recommend putting anything in a tree or shrub planting hole that wasn't there to begin with, says Virginia Cooperative Extension agent Bill Dimock.

If you amend a planting hole, you help create what research calls ``lazy roots.'' The root system grows to the edge of the amended planting hole, then stops when it bumps into the native soil. The tree may look fine the first year or two, but the tree won't develop the root system it needs to withstand drought, wind and such.

``Confining the root ball to such a small space causes problems, especially during periods of heavy rain,'' says Dimock. ``Root suffocation and rot usually ensue.''

Instead, you should dig the hole two to three times as wide as the root ball and no deeper. Plant the tree so the top of the root ball is level with the ground's surface.

Put the native soil back into the planting hole. Then, place a 1- to 2-inch layer of mulch on top to preserve water, maintain an even temperature and reduce weeds that can compete for available nutrients and water.

Always select a plant that will tolerate its environment.

On the other hand: It is advisable to thoroughly work organic matter into a large planting area where you will put in a series of plants.