The Botany of Pruning
It’s important to know something about how plants grow before you head for the garden armed with loppers and a saw. In a nutshell, pruning doesn’t just affect a plant’s size it affects the way a plant grows. If you have a little understanding of plant anatomy and physiology you can prune to get plants to branch in precise ways and to control plant growth, faster or slower. Pruning is one of the most important cultural practices for maintaining plants. It involves both art and science: art in making the pruning cuts properly, and science in knowing how and when to prune for maximum benefits.
First the science…
- All new growth comes from buds. When a seed germinates and grows, only one growing point exists, the apex or terminal bud. Plants grow up and out from the terminal bud. As the plant elongates, structures called nodes are formed. One to three lateral buds are produced at each of these nodes. Lateral buds are arranged along branches in different ways-either opposite or alternate-depending on the plant. These buds, which become leaves, are separated by sections of branch called internodes.
- An important thing to remember is that all plants have hormones and they run the show. Terminal buds produce hormones that suppress the growth of the lateral buds below the tip, an effect botanists call apical dominance. If you cut off the terminal bud, which stops the production of these hormones, then the lateral buds closest to the cut are signaled to grow. This is how you get a plant to branch out and become more rounded and full in form.
- The vigor of the new growth is also influenced by where you cut. The farther back you cut a shoot, the more robust the new growth. Pinch out the growing tip of a stem and the effect is modest; cut back a shoot by two thirds and the result is an onslaught of sprouting lateral buds.
- Pruning usually produces more shoots and leaves and fewer flowers and fruits. Severe pruning, especially of young plants, can mean no flowers and fruits for several years.
- saw or loppers
1. Determine when you need to prune your plant. A rule of thumb is the worst time to prune is in the spring immediately after new growth has developed, because you’re removing the foliage that is replenishing the plant’s food supply. The late dormant season-just before new growth begins-is the best time for pruning most woody and evergreen plants. You should plan to prune flowering shrubs and plants right after they flower.
2. Get the right-size pruning tool for the job, and keep it sharp so you can make clean cuts. Successful pruning requires that all cuts be made in a way that allows the plant to close off the wound and resume healthy growth. Before thinning out a branch, look closely at its structure. You will recognize the branch collar, a slight swollen area at the base of the lower side of the branch, and the bark ridge, a V-shaped region in the top angle between the branch and the main stem to which it is attached. Both the branch collar and the bark ridge must remain intact after the branch is removed, in order for the plant to close off its wound successfully. Never make a flush cut or damage a bud. Rather, locate the branch collar and the bark ridge, and angle your cut appropriately to cut ¼ ” beyond them. Again, it is hormones from the bud that will control the successful healing of pruned branch.
3. Establish your plants best shape and always keep in mind its ultimate size. Remove all of the dead, damaged and diseased parts of the plant. Select several of the strongest branches to form the shape of the plant and remove all the others.
4. Plan to maintain the health of your plant by pruning annually so each main branch adds enough stems to keep the plant full. Remove any new branches that grow at odd angles or old branches that are damaged or diseased, and don’t contribute enough foliage to maintain the shape.