Water is essential to all plant life, but trees, the giants of the plant world, require exceptional amounts. A tree large enought to provide shade in the right place is priceless. Well established with a good root system, it has a large area upon which to draw to satisfy its thirst. If it doesn't rain for quite a while, it doesn't suffer greatly.

Most new homes, and many older ones, do not have such trees; they must wait for young trees to grow up. Many home-owners plant less-desirable kinds becuase they are faster-growing.

Frequently, the newly planted tree stands still for three or four years, making little of no growth. This is often because the tree doesn't have a good root system in the new location.

The young tree needs at least an inch of rainfall during a week, and if it doesn't get it, it should be watered enough to make up the deficit.

If the tree is planted on the lawn, eliminate grass from a 12-foot circle arond it. Then the tree roots won't have to compete with grass roots for water and nutrients.

For the tree roots to grow and increase in length, they must invade soil occupied by grass roots. There is competition for space, and the grass roots have the advantage because they are well developed and able to hold their own for a year or two or even longer.

It's a growth characteristic of lawn grasses that permits the tree to win out finally: A grass root doesn't live very long -- older roots are always dying and new ones developing.

Tree roots, on the ohter hand, are basically much longer- lived. Over a period of time, as changes take place with the grass roots, the tree roots are able to become established and dominate the space.

As with all green plants, trees start their growth by taking in the materials that are combined chemically to make the wood, bark and leaves. Water is one of the essential growth elements.

Water, nitrates and minerals are absorbed from the soil in water solution. They cannot enter trees in any other form. Even the carbon dioxide that the trees extract from the atmosphere passes into the water solution as soon as it enters the cells of the leaves.

Once inside the tree, all movement of materials takes place in water solution and all chemical reactions take place in water. Q: We were away this spring and didn't get to plant azaleas. Can it be done during the summer? A: Azaleas can be planted and transplanted almost any time of the year; summer is not a very good time, but it can be done successfully if they are handled carefully and given plenty of water during hot, dry weather. Don't let them dry out. Q: This past spring I planted Blackseeded Simpson and salad-bowl lettuce in my garden. They are badly infested with tiny black bugs. How can I get rid of them? A: They are aphids. Turn the hose on them full force and wash them off. Q: How late in the summer can we plant gladiolus to have blooms before frost? A: Some varieties bloom in 60 days, some in 70 and some in 80. If planted on July 1, the 80-day ones would bloom about September 15. Q: We sprayed our dwarf apple trees and about an hour later it rained hard. Should we have sprayed all over again? A: Sprays are mixtures of pesticides and water, and if they do not dry before it rains, they are washed off. After the spray has dried it will adhre to the plant for a considerable time. Q: Is it necessary to cut off faded rhododendron blossoms after they finish blooming? A: One expert estimated that it took seven times as much energy (food) for the rhododendron to form seed pods as to bloom. However, rhododendrons growing wild bloom beautifully every year and no one picks off their faded flowers.