Tropical Gardening: Hurricane season means need for tree care

The saying “August a must, September remember, and October all over” is an old sailors warning when it comes to hurricanes, so it’s time for our garden checkup to see what trees and shrubs need special care.

We already have had five storms develop this season and it looks like more to come. Pruning is important, as is proper irrigation and fertilization.

By proper pruning, you also will 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.

Even if you were careful to select the right trees for your yard, and shade lovers for underneath, there comes a time when you have to consider pruning.

Whatever the natural form is in the beginning, it should be maintained, and that means individual handling of each problem. Trees should be pruned in such a manner as to remove enough of the canopy so as to allow gale force winds through the tree.

Most tree experts agree heavily topped, or “hatracked,” trees will be more susceptible to damage from disease and insect attacks in the long run, so this practice is not recommended.

When it comes to palms, excessive removal of leaves also is a bad practice. Large fruited types such as the coconut might have fruit and inflorescences removed. Removing too many leaves actually will weaken the tree in the long run and cause a condition called “pencil top.” Several disease problems also are aggravated by excessive pruning.

In locations where rainfall is deficient, watch out for stress because of lack of water. This can be seen in many landscapes of lower Kona, Kohala, Waimea and Ka‘u.

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 also will need a pair of loppers for cutting branches up to three-fourths of an inch in diameter, and a pruning saw.

Pruning should be done for a purpose, to maintain shape, remove diseased or awkward branches or to reduce the size of a vigorous grower, such as 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.

Occasionally, summer can be wet or windy, especially if we get one of those nasty storms. Trees likely to be damaged during periods of high winds should be pruned to decrease damage caused by the storms.

Of course, weak and diseased branches and twigs should be removed at any time noted.

Citrus trees can be gone over lightly two or three times a year. Such pruning is done from the inside. Dead wood and “water shoots” or suckers should be removed as they appear. When a weak or unwanted branch is removed, it 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 might need some pruning, too. This is best done after hurricane season.

The King Kamehameha Kona Beach Hotel had to deal with this problem several years ago.

The famous Indian Banyan tree on the makai side of the hotel actually was lifting the corner of the building. With love and respect for trees, the hotel was between the devil and the deep blue sea, as the saying goes. The question was, how could we save the building and at the same time protect the tree?

A certified arborist was called in and, together, with the support of the hotel folks and the community, they solved the problem.

The Moreton Bay banyan just south of the Fish Hopper Restaurant is another at risk now. It seriously needs attention. Water and fertilizer is essential to bringing it back to a healthy condition.

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 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, shrub and flower roots suffer. Of course, if the trees were planted too close to a building or cesspool, then it could cause considerable damage.

The first step is to dig into the soil alongside the lawn or flower bed where the trees grow. After just a few spades full, 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, flower bed, structure or cesspool and the tree with a rented power trencher.

On the other hand, if you find a number of roots the thickness of your arm and bigger, the trencher machine probably won’t work. Unless the roots are exceptionally soft, the machine will bind on the thick wood and not do a satisfactory job. If that’s the case, you have a more difficult task on your hands.

Dig the trench by hand, to about 2 feet deep. Then, sever sections of the roots within the trench. Use an ax 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.

Pruning trees and their roots can be dangerous, so if the job is major, it is better to call in a qualified arborist to do the work. This also will aid you in avoiding a butcher job that will cost a lot more in the long run.

When it comes to fertilization, it is better to keep it on the light side until late fall. Then, an application of a complete fertilizer containing nitrogen, phosphorus and potassium plus trace elements will carry trees until spring.

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, fertilization and irrigation is a must.

This information is supplied by the University of Hawaii College of Tropical Agriculture and Human Resources. For further information, contact the office near you.