The following parts of a tree are important for an understanding of proper tree pruning (Figure 11-6). The lead branch of a tree is its most important branch. It is dominant over the other branches called the scaffold branches. The lead branch usually cannot be removed without destroying the distinctive shape of the tree. This is especially true in young trees.
The scaffold branches create the canopy, or foliage, of the tree. The amount of shade cast by the canopy is directly related to the number of scaffold branches and the size of the leaves. When it becomes necessary to remove a branch from a tree, removal usually occurs at a crotch, the point at which a branch meets the trunk of the tree or another, larger branch.
figure 11-6. The parts of a tree (Delmar/ figure 11-7. Tree crotch structure (Delmar/Cengage Learning)
It is always desirable to leave the strongest branches and remove the weakest. Where the crotch union is wide (approaching a right angle), the branch is strong because there has been no crowding and pinching of the new wood produced each year by the cambiums of the trunk and branches. Where the crotch union is narrow, the branch is weak due to a pinch point forming where the expanding trunk meets the expanding branch (Figure 11-7). Growth in that area becomes compressed and dwarfed, and the branch may snap off at that point during a heavy wind or in response to the weight of a person climbing on it.
Two other types of branches often found on trees are suckers and water sprouts. Suckers originate from the underground root system. Water sprouts develop along the trunk and branches of a tree. Neither is desirable for an attractive tree and both should be removed.