Some important things to know when pruning trees

On Maui, you often see very severe tree pruning, leaving nothing but stubs. And while some badly pruned trees can be pretty forgiving, to promote good health through the life of the tree, there are some important things to know when pruning trees.

These include knowing what and where to cut, how much to cut and when to cut. Incorrect pruning, such as “topping” can do more harm than good to your trees. Topping refers to cutting trees back to stubs, which are uniform in height.

Some of the reasons that topping is bad for trees include the creation of large wounds in the tree, opening them up to attacks by diseases and insects. Removing large amounts of foliage reduces photosynthesis, which is how trees produce their own food. In addition, the stubs that are left behind may be more prone to wind and storm damage, creating a hazard.

Be sure you have the right tools for the job. Bypass pruning shears work best for cutting branches up to a half inch in diameter. Loppers are best used for branches up to 1-inch in diameter, while pruning saws can be used for branches more than 2 inches.

Before you begin, remember not to remove more than 25 percent of the canopy at one time. When removing a branch, be sure to stay outside the branch collar. Often, the collar is easy to see. If it’s not visible, the cut should be angled away from the trunk outside the bark ridge. When removing larger branches, there needs to be a series of cuts to prevent the tearing of bark along the trunk. When pruned properly, trees are able to “compartmentalize.” In other words they form a callus, or a protective boundary, at the site of the cut to prevent the invasion of insects and diseases. Because trees have this ability, tree paint is unnecessary.

When deciding what to remove from a tree, first start with dead or diseased branches. Take the time to sanitize the tools between cuts when removing diseased branches. This can be done with 70 percent isopropyl alcohol. The next thing to look for is branches that are crossing each other. Choose to keep the stronger branch that is growing in the direction that works for the tree. General speaking, it’s a good idea for branches to face outwards from the canopy. Removing interior branches allows for more light to penetrate the tree canopy and helps prevent diseases by allowing good airflow through the tree.

Newly planted trees should be minimally pruned. Newly planted trees should be using all their energy developing roots. If pruning is done at planting time, the tree will expend a great deal of energy on forming callus instead of on root growth. More intensive pruning can be done after the second or third year.

Deciduous trees, such as monkeypod, should be pruned late in the dormant season. Trees that keep their leaves should be pruned several weeks after the flush of new growth. Fruit trees, such as mango and lychee, should be pruned after fruiting and before a flush of new growth begins. Fruit trees should not be pruned once flowering begins.

If you are interested in learning more about gardening and are looking for an opportunity to volunteer in your community, consider applying for the University of Hawaii Master Gardener Program.

This nationally recognized program is active in all 50 states and began in Hawaii in 1988. The next 16-week training begins in mid-January 2014. Training includes information on soils, basic botany, plant pests and diseases and other plant care information.

After completing the training, master gardener interns are required to volunteer a minimum of 50 hours in the first year to receive their certification. Volunteer activities include staffing booths at fairs and festivals, hosting plant clinics and plant sales, conducting workshops, and developing and maintaining community and educational gardens.

Applications for the program will be available in the first week of October. If you are interested in becoming a Master Gardener volunteer, contact me at my email address below.

* Lorraine Brooks is an urban horticulture extension agent and the Maui Master Gardener coordinator with the University of Hawaii’s Cooperative Extension Service, part of the College of Tropical Agriculture and Human Resources. Her email is Gardening In Maui will run when there is a fifth Sunday of the month.