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Basic Palm Health and Management

Basic Palm Health and Management
Article by: Jessica Warren, ANR Agent, Camden County

One of the perks of living on the coast is palm trees. Our native cabbage palm grows wild in our maritime forests, and a variety of species are integrated into commercial and residential landscapes. There’s nothing else that gives you the laid-back feeling of being at the coast like a palm does. Interestingly palm trees aren’t trees at all, but woody grasses. Palms have adventitious root systems unlike true trees, which allows them to be transplanted successfully at a much larger size. Palms have one growing point that is located at the top of the trunk, the apical meristem. All new leaves and flowers develop from the apical meristem, and death of the apical meristem kills the entire palm (in single stemmed species which we typically see in our area). Stem (trunk) wounds that would be compartmentalized and grown over in trees, are permanent in palms.

Palms should be planted at the same depth that they were growing in the container or nursery. Often palms are planted too deeply which leads to mortality. After transplanting, palms should be watered daily for the first month, and for the first 4-6 months the root ball and backfill should be kept moist but not saturated. It may take up to a year for palms to become established.

Palms, especially non-native palms, need routine fertilization. That being said, it’s important to exercise caution as overfertilization can be lethal to palms. Slow-release fertilizers are best, and it’s important to use fertilizers formulated for palms which usually have analysis of 8-2-12+4mg. Fertilizer should be evenly distributed under the full canopy of the palm and fertilizer spikes should be avoided. 8-2-12 is a good fertilizer ratio to use throughout the lawn and landscape that will help minimize the risk of fertilizer damage to your palms. Lawn and landscape fertilizers can be inadvertently taken up by palms causing toxicity issues, as excessive nitrogen can induce potassium deficiency in palms and cause mortality. Fertilize palms every three months during the growing season (not in winter).

Nutrient deficiencies are one of the most common issues of palms, and potassium deficiency is the most common nutritional disorder. Symptoms of potassium deficiency appear on the oldest leaves as the plant pulls nutrients from the older leaves to utilize in other parts of the plant. Because of this recycling of nutrients, leaves should not be pruned out unless they are completely brown and dead. Correction of nutrient deficiencies can take up to 2-3 years for some elements.

Improper pruning is, unfortunately, a common practice with palms. Palms should have a 360-degree crown. Hurricane cuts are detrimental to the health of the palm, and research shows that this pruning style makes the palm less resilient to storms. Pruning is not necessary for the health of the palm, and if done incorrectly, can cause permanent damage or mortality. If you choose to prune, only completely dead, brown leaves should be removed. Removing leaves that aren’t completely dead induces the release of chemical signals that attract insect pests that can be lethal. Over pruning increases susceptibility to cold and storm damage. Pruning can cause nutrient deficiencies, smaller growth, reduced wildlife habitat (many species including some native bats use palm trees as roosts) and an entry point for pests and diseases. Though pruning leaves is discouraged, removal of living flowers or fruit stalks is not an issue and can direct more energy back into the plant for strength and stability. Boots (old leaf sheaths) do not need to be removed. If leaves are removed, they should be cut close to the trunk but exercise caution not to cut into the trunk. Pruning tools should be disinfected between trees to reduce the spread of disease. Climbing spikes should never be used to prune palms. The damage that they cause to the trunk will never heal and will serve as an entry point for insects and disease.

There are a few insect pests of palms, but only one of significant concern. Palmetto weevils are the largest weevil in North America and affect a variety of palm species. Though they typically attack wounded, stressed or dying palms, they will attack healthy Canary Island date palms. Palmetto weevils are attracted when palms release chemicals that signal stress or wounding. Symptoms can vary but involve an irreversible decline of the canopy. As the damage continues, the rot that is associated with the infestation causes the top of the palm to fall over. The best course of action is to remove the palm as soon as the palmetto weevil infestation is confirmed. Palmetto weevils are extremely difficult to prevent or treat, therefore the best defense is good tree management.

Cabbage palm caterpillars affect cabbage palms (also known as sabal palms). These caterpillars are not lethal to palms and are probably more annoying to people than palms. Cabbage palm caterpillars are the larva of an owlet moth and are difficult to manage or prevent. These caterpillars may invade structures in search of pupation sites leaving a reddish-brown trail of fluid that can be staining. They will also sometimes chew on furniture and other objects to incorporate pieces of the debris into their cocoons.

There are several diseases that can affect palms. Lethal bronzing is a disease caused by a phytoplasma that has not yet been confirmed in Georgia but is active just across the state line. Lethal bronzing symptoms are discoloration starting with the oldest leaves that gradually moves to the younger leaves. A laboratory test is necessary to confirm lethal bronzing, and once a tree tests positive it should be removed immediately.

Ganoderma butt rot is caused by a fungus and all palms are considered hosts. The symptoms of Ganoderma butt rot include wilting or a general decline. A hard, shelf-like fungus (conk) may appear on the trunk, but not all palms with the disease produce conks. The fungus is spread by spores that are produced by the conk, so it is important to remove the tree and any conks as soon as they are observed. The fungus survives in the soil, so it is not advisable to plant another palm in the same location. There is no treatment or prevention for this disease.

In addition to the issues that palms can have, you may also see some normal abnormalities – things that may cause concern but are perfectly normal and harmless for the palm. One of these normal abnormalities is a large root initiation zone. Palm roots are adventitious – they arise from the stem tissue, not from other roots. As a palm grows, its root initiation zone on the trunk expands outward and upward. This can result in a root initiation zone that sometimes spreads several feet up the trunk. Sometimes as the root initiation zone expands above the soil line, new roots can also force bark to flare out and split. Another issue that causes some homeowners concern is irregular boot, or leaf base, shedding, or shedding in an irregular pattern. Individual palms shed their boots at different times and in different patterns based on a variety of factors such as genetics. Trunk erosion is also an unworthy cause for concern.

For the lowest maintenance and least expensive palm experience, plant our native palm (the cabbage palm) and palmettos. They are the most resilient to our climate and the least susceptible to fatal pests and diseases. They also offer the best habitat for our native wildlife. I know a lot of people who put up bat houses to try to attract bats to their landscape. Better than a bat house (which only appeals to cave dwelling species) would be an unpruned palm in the landscape to serve as habitat for our many tree dwelling bat species here on the coast.