Everywhere I go this October I see trees and shrubs on sale. In some cases prices have been slashed up to 75 percent. Fall is a great time to buy plants. Just make sure you buy them from a reputable store where they've been regularly cared for during the growing season.

The biggest favor you can do for your new plants when you get them home is to plant them correctly. Be sure to dig a hole that is wider than deep and plant your bargains with the top of the root ball as close to ground level as possible. Planting holes should be two to three times wider than deep.

Inspect the root system of your containerized or balled and burlapped plant carefully as it goes into the ground. Recent research conducted at the University of Minnesota indicates that many trees develop problems that shorten their lifespan because they are planted too deeply. Of particular concern are roots that might girdle the main trunk or stem as they develop.

Why is this important? Only half of each plant, the shoot system, grows above-ground. The other half, the root system, grows underground where it is often out of mind as well as out of sight.

Roots perform many vital functions and have a profound effect on overall plant health. Most people think of tree roots as an anchor, growing straight down. In reality, most tree roots are located in the top 16 to 24 inches of soil and occupy an area 2 to 4 times the diameter of the tree crown. Loosening that soil at planting time aids in future root growth.

In addition to anchoring plants, roots transport water and minerals from the soil to the rest of the tree. Water and minerals are used to manufacture carbohydrates which are then stored as reserves in the root system to produce spring foliage.

When plants are grown incorrectly in the nursery or spend too long in a container they often develop root systems that can threaten future plant health. These roots are known as stem girdling roots or SGRs. This happens because roots are often forced into an encircling growth pattern when trees are grown in containers or held as balled and burlapped stock. If trees are then planted too deeply, the encircling roots can eventually enlarge, compressing (girdling) the stem and damaging bark and wood tissue.

Above-ground symptoms often take 15 or 20 years to show up and most often include stunting of the foliage, decreased annual twig growth and a smaller trunk diameter. Trees with stem girdling roots often lean to one side and may have leaves that are scorched (brown) along the edges.

Most deciduous tree trunks normally flare or expand near the ground. Trees suffering from girdling roots often lack trunk flares, going straight into the ground like telephone poles.

If on inspection you discover that your new tree has encircling roots, simply prune them off. Then plant your tree so that the flare where roots meet stem is at or only slightly below the soil surface. If your inspection shows more than 1 to 2 inches of soil over the root flare, plant the tree higher than normal in the landscape. When the root collar flare and stem are at or above the soil surface developing stem girdling roots will be easily detectable and treatable long before they cause stress to the tree.

When planting, don't amend the backfill with peat moss, compost or other organics. Research has shown that drainage problems and reduced growth can occur from amended soils. Do be sure to provide the equivalent of an inch of rainfall weekly for the first two years after planting. Most of all, be sure to enjoy. There's nothing quite like the feeling that comes from planting something that will live for a hundred years or more.

For more information on planting trees call UNH Cooperative Extension's Family, Home & Garden Education Center 's Info-Line toll free at 1-877-398-4769 and ask for a copy of the fact sheet, "Steps to Follow When Planting Trees and Shrubs". Trained volunteers are also available to answer your questions Monday through Friday from 9:00am to 2:00pm.

By Margaret Hagen, UNH Cooperative Extension Educator, Hillsborough County