Trees should only be pruned when there is a good and clear reason for doing so and , fortunately,the number of such reasons is small. Pruning involves the cutting away of obergrown and unwanted branches, and the inexperienced gardener can be encouraged by the thought that more damage results from doing it unnecessarily than from leaving the tree to grow in its own way.

First, pruning may be done to make sure that trees have a desired shape or size. The object may be to get a tree of the right height, and at the same time to help the growth of small side branches which will thicken its appearance or give it a special shape. Secondly, pruning may be done to make the tree healthier. You may cut diseaed or dead wood, or branches that are rubbing against each other and thus cause wounds. The health of a tree may be encouraged by removing branches that are blocking up the centre and so preventing the free movement of air.

One result of pruning is that an open wound is left on the tree and this provides an easy entry for disease, but itis a wound that will heal. Often there is a race between the healing and the desease as to whether the tree will live or die, so that there is a period when the tree is at risk. It should be the aim of every gardener to reduce which has been pruned smooth and clean, for healing will be slowed down by roughness. You should allow the cut surface to dry for a few hurs and then paint it with one of the substances available from garden shops produced especially for this purpose. Pruning is usually without interference from the leaves and also it is very unlikely that the cuts yu make will bleed. If this does happen,it is, of course,impossible to paint them properly.

1.Pruning should be done to ______.
a.make the tree grow taller
b.improve the shape of the tree
c.get rid of the small branches
d.make the small branches thicker
2.Trees become unhealthy if the gardener ______.
a.allows too many branches to grow in the middle
b.does not protect them from wind
c.forces them to grow too quickly
d.damages some of the small side branches
3.Why is a special substance painted on the tree?
a.To make a wound smooth
b.To prevent disease entering a wound
c.To cover a rough surface
d.To help a wound to dry
4.A good gardener prunes a tree______.
a.at intervals throughout the year
b.as quickly as possible
c.occasionally when necessary
d.regular every winter
5.What was the author's purpose when writing this passage?
a.To give pratical instruction for pruning a tree.
b.To give a general description of pruning
c.To explain how trees develop diseases
d.To discuss different methods of pruning.

答案：babca