Caring for Landscape Trees in the Garden

The components of a tree can be divided into three main parts: the root system, the leaves and the woody “skeleton” that connects them. The function of the root system is to provide the raw materials necessary for growth such as mineral salts, dissolved in water, to the tree. The leaves perform photosynthesis though the absorption of carbon dioxide from the surrounding air and using the energy from the sun, convert this into the simple sugars. These sugars are then combined with the moisture from the roots to give the tree its nutrients.

The trunk, limbs, branches and twigs act as the tree’s skeleton to hold the leaves in position so that they receive the life-giving sunlight and air. They are also used for transportation as they carry raw materials between the roots and leaves. Capillary attraction pulls up the materials absorbed through the roots and this is also assisted by the osmotic action induced by the evaporation of water from the leaves. This loss of water through the leaves is known as transpiration. On any summer day, a birch tree can transpire between 700 to 900 gallons of water.This is what causes the sap to continuously flow from the roots to the twigs at the very top of the tree.

A gardener’s most important consideration is to protect the tree’s root structure, especially when the tree is to be transplanted or preserved on a building site. The larger roots close to the stem are the tree’s “anchor” and the fine root hairs at the ends of the smaller roots are those responsible for water absorption.

The stem or trunk of a tree is made of three parts: the bark, the wood and the pith. The pith is the central part and is surrounded by the wood. Between the wood and bark is the cambium which is a thin layer that produces new wood and bark. Should the cambium ring be severed, for example, by a wire cable, the tree will die. As the cambium protects the tree against insects and disease, anything driven into it can severely damage the tree.

There are many things that can cause damage to a tree, including man. There are around 200,000 known species of insects that are known to attack and damage trees. As well as these, there are diseases such as blight, rust and rot, and natural occurrences such as storms, fires and droughts can also damage a tree. As some form of balance, birds help to control the spread of caterpillars, borers, harmful beetles and other insects that are likely to damage the tree.

Feeding Trees

In nature, trees grow and shed their leaves. These leaves decay, forming a good soil for the tree. These leaves also assist in preserving moisture in the soil. When a tree is grown on a lawn or backyard, it must compete with the grass for its nutrients and moisture. Leaves are raked up to prevent problems with the grass. As such, a successful gardener would be well advised to supplement the tree’s nutrients every two to three years.

This feeding should be done when the ground is easily “worked”, preferably in the spring or in the fall. A difficult but nonetheless worthwhile way of feeding is to strip the grass from an area all around the tree at least 2 to 3 feet beyond the outer branches, as the root system extends this far. Apply stable (horse) or barnyard (cow or chicken)manure to this area, ensuring that it is around 3 inches thick and then dig it in. After this is done, firm down the soil, rake it level and replace the grass.

One of the easy and simple backyard ideas is to drill holes over the same area, 12 to 18 inches deep and spaced about 15 inches apart, then fill each of these holes with a prepared fertilizer made from bone meal, tankage, peat moss or humus plus chemicals, in a formula equivalent to 10% nitrogen,6% phosphoric acid and 4% potash.

Water and Trees

During the hotter days of summer, landscaping lawns along with specimen trees must be given a deep watering at least every 10 days to counteract the effects of transpiration and reduce stress on the tree. Light watering is inadequate, as the roots are very deep, so the hose or sprinkler should be left to run for at least an hour. Loosen soil that is compacted with a garden fork or similar and in the case of a large tree, holes of about 1 1/2 inches in diameter, 3 to 5 inches deep and 3 feet apart should be bored into the soil around the perimeter of the outer branches. The hose should be covered with sacking and left to run, or alternatively use a canvas hose. A good idea when planting a new tree is to place a piece of hose into the hole over draining tiles and this will ensure that water reaches the subsoil around the tree’s roots. The drain holes should be covered with stones to avoid evaporation.