Pruning Techniques

Pruning inevitably damages plants. When done properly, however, the wounds will seal over quickly and completely. Proper pruning also reduces the risk of rot caused by invading micro-organisms. Hence the importance of knowing where and how to prune.

Removing a branch near the trunk

When cutting off a branch near the trunk, it is important not to remove the branch bark ridge or the branch collar. If you look carefully, you will see that where the branch meets the trunk there is an elongated, wrinkled area, called the branch bark ridge.

At the base and on the sides of the branch is a swelling, varying in size depending on the tree species, called the branch collar.

The collar is formed of growing tissues that will help the cut to seal over. These two points are where the branch tissue meets the trunk tissue. To protect them, cut only the branch and not any part of the trunk. This will allow the wound to seal over faster and limit the risk of internal decay. (Figure 2)

Flush or close cuts should be avoided, as should cuts too far out, which would leave a stub. A stub is the broken or cut base of a branch projecting from a tree trunk.

A stub prevents woundwood Trees and shrubs seal their wounds by producing woundwood, also called callus tissue, which starts forming around the cut and grows inward to cover it.
The woundwood is produced by the remaining live cambium around the cut. If any of the cambium is destroyed, the wound cannot seal over completely.

The cambium is a thin layer of dividing cells under the bark. It is what causes the trunk and branches to grow in diameter. from growing fully over the pruning cut and provides an entry for micro-organisms, fungi and insect pests.

The cut should be clean and straight, on a slightly oblique angle, at about the same angle to the trunk as the branch bark ridge. This sort of cut will allow woundwood to form around and gradually over the cut. It will also help keep rainwater from accumulating.

Figure 1 - Tree Structure	Figure 2 - Removing a branch near the trunk

Special case: Removing a large branch

Branches larger than 4 cm around should be removed in three stages to prevent them from tearing any of the trunk tissue as they come off.

• Make a cut on the underside of the branch, about 30 to 45 cm from the branch collar. Cut only one-third of the way through the branch.
• Make a second cut on the top side of the branch, about 5 cm farther out on the limb. The limb will fall when the two cuts meet.
• Remove the remaining stub A stub is the broken or cut base of a branch projecting from a tree trunk., cutting it at the angle described above. (Figure 3)

Figure 3 - Removing a large branch	Figure 4 - Directional pruning

Trimming back a branch or twig

When trimming back a twig (3 cm or less in diameter) or a branch, directional pruning is always best. This encourages the pruned twig or branch to grow in a desirable direction. (Figure 4)

To trim back a twig, cut it on about a 30° angle, a few millimetres above a lateral bud. (Figure 5) Always cut a branch back to a side branch, being careful not to damage the branch bark ridge.

The bud or side branch acts as a sap drawer, redirecting the sap while discouraging water sprouts.A water sprout is a vigorous upright shoot rising from the trunk or branches.
Water sprouts draw large amounts of sap, competing with neighbouring branches. They are also weakly anchored and vulnerable to wind and ice damage.
Over-pruning encourages heavy growth of water sprouts. In addition, the sap flow around the wound will cause it to seal over more quickly.

In addition, the sap flow around the wound will cause it to seal over more quickly. (Figure 6)

The diameter of the sap drawer must be at least one-third that of the pruned branch, or it could dry out.

Figure 5 - Trimming back a twig	Figure 6 - Pruning with sap drawer