Wednesday | December 13, 2017
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Pruning for right reasons

The one garden activity that gives many gardeners feelings of trepidation and uncertainty is pruning.

In the natural world, trees and shrubs find their natural niche, compete for space and light and find a balance for survival. In gardens, however, we try to maximize our square footage, the number of species and varieties we grow. We mold our plants into what we envision as the perfect garden.

In its simplest form, pruning improves form and function of your plants in the garden and landscape. While most of us associate pruning with trees and shrubs, it can be practiced with vegetables, vines and annual ornamentals. Entire books have been written on pruning. I can’t cover everything, but these are some highlights.

Whether you know it or not, many of you have pruned plants. Removal of dead flowers to promote more flowers is a form of pruning referred to as deadheading. In many annual flowering plants, seed production is the natural outcome of flowering and when the hormonal influence of seed development is removed, the plant automatically reverts to the flowering mode. The removal of the primary growing point to create a bushy plant and more flowering is another form of pruning, as is removing side buds and shoots to stimulate a larger primary flower.

Large landscape trees are often pruned to maintain their size and shape. When pruning to improve tree form and function, it is important to consider angles that promote strong branching. The creation of bonsai plants requires careful pruning and training of plants.

Sometimes, we prune to stimulate the production of new growth, flowering and fruiting as old branches are removed to allow new ones to take their place. Removal of unwanted growth, diseased or infested branches, and broken limbs are other reasons to prune plants. Unwanted growth is often removed to prevent branches and leaves from falling on buildings and vehicles, to improve line of sight and to allow more light to penetrate the canopy. Pruning can also be done to resize trees and shrubs that were allowed to outgrow their space.

You will need a few tools to successfully complete a pruning job. Hand shears are essential for general pruning in the garden. Pruning shears come in two general types, bypass and anvil. Bypass shears work like scissors and anvil types work like a knife on a cutting board. Both will cut branches 0.25 to 0.5 inches in diameter with little difficulty depending on blade size and leverage the handles create on the cutting blade. Lopping shears are great for cutting larger branches up to 1.5 inches in diameter. For larger branches, a pruning saw or chain saw will be indispensable. For neater cuts, finer saw blades are needed. A pole pruner and saw allows you to stand on the ground while working. It is important when cutting large branches that you conduct a triple cut to prevent stripping the tree’s bark. Make a cut one-third of the way through the branch on the bottom side, 1 foot from the final cut. The second cut is made to the outside of the first. Remove the 1-foot stub with the final cut. Since the majority of the weight is removed from the branch, the chance of tearing the bark is greatly reduced.

Whether you are standing on firm ground pruning a rose bush, on a ladder or in a lift bucket, always remember safety first. The proper gear includes eye protection, gloves and shoes. Pruning while standing on the ground is always a good option. When pruning from a ladder, firmly position the ladder. Do not overreach; it is better to move the ladder than fall over with it. Keep fingers away from the cutting blades, especially with single-hand tools such as pruning shears. When pruning overhead, be aware of falling branches and fruit, as well as electrical, cable and phone lines.

For more information on this and other gardening topics, visit the University of Hawaii College of Tropical Agriculture and Human Resources electronic publication website at or any Cooperative Extension Service office. The Cooperative Extension Service office Master Gardener program is also a good resource for more information.

Russell Nagata is the Hawaii County administrator of the University of Hawaii at Manoa College of Tropical Agriculture and Human Resources. He can be reached at