Diana Duff is a plant adviser, educator and consultant with an organic farm in Captain Cook.
BY DIANA DUFF | SPECIAL TO WEST HAWAII TODAY
Winter is usually a dormant season for plants. Though tropical plants may continue to flower or fruit in early winter, most will produce fewer flowers and less new growth during January and February when we have colder temperatures and shorter days. This is as close to a dormant period as we might find here.
Pruning well is not difficult and can provide many benefits to you and your plants. With a few guidelines, pruning can provide the satisfaction of being in control of future growth while enhancing the appearance of the shrubs and trees in your garden. Good pruning also benefits plant health when you remove dead, diseased and disfigured branches and prevent stress from overgrowth.
In our tropical climate, most plants can tolerate light pruning year-round, but good timing, some knowledge and experience will help when approaching larger shrubs, small trees or specimen plants. Pruning larger trees, especially when it requires climbing or using a ladder or chain saw, is best done by a professional arborist. Hiring a professional is worth it when it means avoiding personal injury.
The first canon of successful pruning is called the “one-third” rule, which advises against pruning more than a third of a plant at a time. The rule applies to all plants, including your lawn. Removing more than one-third of a plant’s leaves, where it produces food through photosynthesis, can be stressful to the plant. Stress can lead to a general decline, which increases the plant’s susceptibility to attack by insects and diseases.
Several other general guidelines apply to pruning shrubs and small trees. Pruning cuts should be made about 1/4 inch above a bud or node that is growing in the direction you want the plant to put out new growth. If you are removing heavy or long branches, be sure to make a three-part cut to avoid tearing the bark at the base of the branch. The first cut should be an undercut at least 10 inches beyond the branch base. The second is a weight reduction cut a few inches farther out on the branch. The final cut is at the base of the branch just outside the swollen joint of the branch to its base or trunk. This area is called the branch collar. A proper cut just outside the branch collar will heal itself without the use of pruning paint into a symmetrical donut shape.
Following the next four guidelines sequentially should result in a good pruning job.
1. Dead. Remove all dead material. Anything that is necrotic (snaps when you bend it) should be removed.
2. Diseased. Any branches or leaves that seem to be infested with insects or disease should be removed. Remember the one-third rule, however. After removing the most severely infected third, treat any remaining infestation in other ways.
3. Disfigured. Remove branches that are broken or growing in ways that do not enhance the plant’s appearance. Remove crossing branches. These may rub against one another causing damage to the outer layer (bark) of the plant, which is responsible for transporting its food and water.
4. Dysfunctional. Branches that detract from the plants fruiting, flowering, appearance or general health should be removed. This includes suckers at the base of the plant. Be sure to remove any vigorous upright growth that may appear below the graft line on grafted trees. Water sprouts, which appear as strong vertical shoots from the plant’s branches, should also be removed. Competing leads in young trees or narrow branch crotches should also be eliminated. In the case of plants grown for flower or fruit production, remove growth that is not productive or prevents production. Since flowering and fruiting varies from plant to plant, be sure to research your particular variety before pruning.
Pruning well involves both art and science. A good pruner has botanical know-how, a good aesthetic sense and lots of practice. Pruning can be very rewarding, so grab your shears, follow the guidelines and enjoy your results.
Tropical
gardening helpline
Lorraine asks: I want to create a 6-foot privacy hedge along my property line. I have several large and beautiful hibiscus plants elsewhere on my property. If I reduce the size of the large plants, can I use the branches I remove to get a hedge started?
Answer: Yes, you can save the cuttings from your pruning job and get good starts for your hedge.
Before you start to prune, you might want to get the medium for your cuttings ready. One of the best rooting mixes consists of one part vermiculite to one part perlite. This provides some water-holding capacity along with good drainage. Vermiculite also has some antifungal properties. Whatever you use, be sure the medium can stay damp without being soggy while the cuttings are developing roots.
As you are pruning your large shrubs select cuttings that are somewhat woody and about the diameter of a pencil for propagating. If you can put them in water right away it will help them stay hydrated until you can place them in the medium. Once you have all the branches cut, you can trim those you selected for propagating into lengths of at least 4 inches with at least four nodes. Remove most of the leaves, dip the bottom end of the cuttings in rooting hormone and sink about half of the stem into the prepared pots. You can put several in each pot since some may not “take.”
Keep the medium moist, but not too wet, and wait. Rooting can take several months.
Once you see new leaves appearing, this means a new root system is starting. If the plants resist being pulled easily from the soil, the roots may be developed enough to transplant. Up potting to a single stem in a larger pot to allow the plants to get better established and grow larger will help ensure success.
Before planting in the garden, place the pots in the area where you want your hedge and keep them watered for a week or two. At this point, they should be well acclimated and ready to go into the ground. It may take several years to get the plants to grow to 6 feet and fill out, but you will have made good use of your prunings and saved the money you might have spent buying lots of new plants.
Email plant questions to konamg@ctahr.hawaii.edu for answers by certified master gardeners. Some questions will be chosen for inclusion in this column.
Diana Duff is a plant adviser, educator and consultant with an organic farm in Captain Cook.