By Norman C. Bezona
Cooperative Extension Service University of Hawaii at Manoa College of Tropical Agriculture and Human Resources
Hurricane force winds are expected during hurricane season, but some of the worst wind damage on our island in recent years has been in March. So it’s a good time to consider some general pruning needs in your garden.
Forget the old sailors’ rhyme, “June, too soon, July, stand by, August, a must, September, remember.” Remember, that with global warming, we are getting an increase in violent storms as well as hurricanes even beyond hurricane season. By proper pruning, you can avoid much of the damage caused by the strong winds of passing storms and cold fronts. Pruning will also increase light availability to understory plants.
Since some light is essential to plant vigor, it is a good idea to open up those heavy canopied trees this time of year before intense summer sun can cause scalding on exposed branches.
Even if we never had storms, and if you were careful to select the right trees for your yard, there comes a time when you have to consider pruning.
Whatever the natural form of the tree is in the beginning, it should be maintained, and this means individual handling of each problem.
Some knowledge of pruning is necessary for the gardener who does his own work. A good set of pruning tools is necessary, including a pair of side-cutters for removing twigs and small branches. You will also need a pair of loppers for cutting branches up to three-fourths of an inch in diameter, a pruning saw, a tree pruner on a pole, and if you prefer, waterproof paint for covering pruning wounds. Some schools of thought believe that pruning paint is of no value, and there is proof that under some conditions, this is the case. Other folks swear that it keeps the bugs and rot out if you are careful to reapply the paint when it begins to deteriorate.
Pruning should be done for a purpose, such as to maintain shape, remove diseased or awkward branches, or to reduce the size of a vigorous grower, like a rubber tree.
Pruning becomes an important chore for several reasons. Trees that respond to day length and bloom during the winter or spring months should be pruned through the summer months. Their final pruning should be before September.
Trees that are likely to be damaged during periods of high winds should be pruned to decrease damage caused by the storms.
Trees should be pruned in such a manner as to remove approximately one-third of the existing branches deep into the canopy of the tree rather than “headed-back” or “hat-racked.”
Plants that are headed-back will normally accumulate a heavier top growth than before and will be more susceptible to storm damage than before. We commonly do this type of pruning with shower trees because they tend to survive severe pruning, but it can lead to disease and insect infestation.
Of course, weak and diseased branches and twigs should be removed at any time noted. Citrus trees may be gone over lightly two or three times a year. Such pruning is done from the inside. Dead wood and vertical “water shoots” or suckers should be removed as they appear. When a weak or unwanted branch is removed from a healthy branch, it is cut off even with the branch itself. Do not leave a stub. This discourages disease and insect damage.
Many of our tropical trees grow rampant with extensive root systems. That’s why we prune to keep them from getting out of hand, but let’s not forget the roots may need some pruning too.
Here’s a scheme for gardeners whose yards are full of trees. It’s a way to keep lawns or flower beds near them healthy, too. The trouble with roots of many big trees such as banyans and eucalyptus is that they are too greedy. Their roots will fill a flower bed or a new lawn in just a few years after the trees were planted.
When this happens, you can be sure that they aren’t doing the smaller plants any good. Very likely, the tree roots are competing so fiercely for soil’s available water and nutrients that grass, shrubs and flower roots suffer.
The first step is to dig into the soil alongside the lawn or flower bed where the trees grow. You can begin to see how many roots grow through the area. If you find many little roots, from thread size to the diameter of your thumb, you can make a trench between the lawn or bed and the tree. Dig the trench by hand about 2 feet deep, then sever sections of the roots within the trench. Use an axe or saw or both.
Whether you are able to make the trench with the machine or are forced to dig and cut by hand depends on how much time the trees have had to send roots into the area and how long it’s been since you thoroughly cultivated the soil.
If roots are buckling a garden walk or patio, dig the trench on the tree side of the paving.
After the trench is made, you can eliminate or greatly reduce the possibility of regrowth into the area by dropping 80-pound asphalt roofing paper into it and then refilling on the tree side of the paper with the excavated soil.
Trees are part of the beauty of our islands. Rather than destroying these valuable assets, work with them. Proper selection of plants to grow under their protective canopy is important. Proper pruning is a must.
One last thought on pruning. Large tree work can be dangerous. Unless you are experienced and have good insurance, don’t tackle the job yourself. Hire a certified arborist, if possible. They know what they are doing. Also be sure whoever you hire has the proper insurance. If you hire someone uninsured and they get hurt, you could have an expensive lawsuit on your hands that could do more damage to your pocketbook than a hurricane!