HOW TO PLANT A TREE
So you've got yourself a tree and a spot to plant it. So dig a hole, drop it in, and fill it up. Simple. Right? Well, yes and no. There are a few things to consider.
The top of the root ball should always be a little above ground level. When planting in clay or poorly drained soil, plant the root ball 1/3 above grade. Place a small amount of soil to the top of the root ball and even off with mulch.
A broad shallow planting hole provides firm support for the root ball. The top of the root ball is slightly above ground level. This maximizes the lateral spread of roots from the upper one-third of the root ball.
UNDERSTANDING TREE GROWING CONDITIONS
The soil environment of the natural forest is usually sheltered, shaded, and tempered. Each year leaves are deposited on the forest floor and, as they decompose, replenish organic matter. This improves soil porosity, releasing nutrients and acidifying the soil.
Landscapes are usually not created on undisturbed soil sites but are more likely to be the result of large-scale modifications of fill soil. This is sub-soil and various combinations do not resemble the natural soil environment in which trees have genetically adapted themselves. Modified home landscape soils have little of the porosity associated with undisturbed soils. In urbanized soil, there is often poor regulation of moisture, poor aeration, and obstacles to root growth, alkalinity, salinity, compaction, and widely fluctuating surface temperatures. Prolonged retention of moisture may lead to anaerobic compounds, which inhibit root growth or are even lethal to roots. Chlorosis (yellowing of leaves) is commonly seen in urban trees.
Many soils are a difficult media in which to transplant trees because rapid lateral root regeneration is often hard to accomplish. The roots of transplanted balled and burlaped trees may not readily enter the surrounding dense soil. Make only one interface for roots to grow across to leave the root ball and enter the surrounding existing soil. To help this, use the existing soil as a backfill. The challenge is to induce rapid rootlet growth into the soil so a favorable root/crown ratio can develop. Since inducement of roots is most effective in the upper six inches where oxygen is adequate, the depth of the outer backfill material need not be very great (see diagram).