Pruning can correct growth problems, remove dead or diseased wood, and maintain the appearance of your plants. As your plants mature you should prune them on a regular basis to keep them healthy and attractive.
We discuss a few types of pruning below, but before we get too specific here are two general cautions about pruning:
1. Plants often respond to pruning by sending out new growth. Whether this new growth is desirable or unhealthy depends on the cuts you make, so it is very important to make good cuts. As a rule, make cuts to branch forks or at least to a bud. Always leave a very small (quarter inch) stub to help the plant heal properly.
2. Good pruning is a skill, and you can only get it by practice, patience, and learning. Take your time, and step back often to look at the plant from a distance. Don’t cut off too much at one time, and learn about the plants you are pruning. Since not all plants react the same to pruning, the more you know about your plants the less likely it is that you’ll make a costly mistake.
Thinning allows light and air into the plant, corrects growth defects, and lets you shape plants without radical surgery. When thinning, look for and remove branches that touch or grow into each other. Remove broken, dead, or diseased branches. Remove any inward growing limbs, as well as any watersprouts or suckers.
Where branches are too thick for your pruning shears, you will need a saw. When sawing, don’t just lop off the problem branch—make three cuts in the branch as illustrated in the diagram. This ensures a clean cut that will heal better, and it also keeps the branch from ripping bark off the tree or shrub when it falls. Branches too thick for hand pruners flush with the tree trunk; cut back just to the ‘branch collar’ which is the swollen ring that surrounds the base of the branch. If you make your cuts this way the tree can cover the wound and retard decline. It isn’t necessary to coat the wound with tree paint.
Renovating involves drastically cutting back a shrub either to reinvigorate it or start over. In most cases renovating is needed because the shrub was not maintained properly to begin with. Not all shrubs will respond to renovating in the same way. Some shrubs will not regrow, others take years to get back to size, and some regrow in a very short time. You should find out about the shrub so you can predict how much cutting it can survive.
• Many deciduous shrubs tolerate total renovation (being cut to the ground) and will regrow quickly. However, unless you are sure that the shrub you want to renovate is tolerant it is best to prune the shrub no more than one-third of the total plant size annually.
• Most needled evergreen shrubs cannot be renovated because they will not regrow on old bare wood.
Shearing should be avoided in most cases because it isn’t good for plants and isn’t very appealing aesthetically (unless you enjoy a very simple shape, like a cube). You can shear plants for a formal appearance, although the same caution applies here as for renovating: find out if your plant can tolerate the surgery. Use hand shears, as they tend to be more forgiving than motorized shears. Try not to shear too much; if the plant’s inner branches get exposed, you’ve gone too far (see Renovating). Gently form the plant so that it is wider at the bottom than at the top so the lower parts receive plenty of sunlight. This will keep the sides lush and thick.