One of the most important palm tree maintenance tasks is pruning. Judging by the palm pruning being performed in our landscapes, you would think pruning palms to a few fronds sticking out of the top of the tree is the right thing to do.
Some companies performing this type of work call it “hurricane pruning.” The name is misleading because it may seem like it is the right thing to do. Not only is hurricane pruning unnecessary, but it can harm your tree.
Most palm species are naturally resistant to wind.
Some of the negative outcomes of overpruning palms are:
- Reduction in the amount of food produced by the leaves, causing the tree to get skinnier and skinnier as it grows.
- Reduced winter hardiness.
- Nutrient deficiencies.
- Spreading of disease.
How should palms be pruned? Ideally, a healthy palm has a canopy almost 360 degrees around, or circular in shape. However, this is rare in our landscapes as folks feel the need to create a more formal look.
The best method is to prune out only dead fronds. Fruit and flower stalks can be pruned at any time. You may be tempted to remove lower fronds that are discolored—a sign of a nutrient deficiency. Resist this temptation. The palm is moving the scarce nutrients from the older fronds to the newer fronds. Pruning out these “ugly” fronds causes the tree to mine nutrients from the next level of fronds, causing them to look deficient. It is a harmful cycle that usually results in the death of the tree.
If you have a palm with nutrient-deficient fronds, the best fertilizer is an 8-2-12 palm fertilizer with slow-release nitrogen potassium, magnesium and phosphorus. The nutrients are coated so they are released over a longer period. The rate is 1.5 pounds of palm fertilizer per 100 square feet of area treated, applied four times a year.
Prune fronds no higher than horizontal—9 and 3 on a clock face. Otherwise, you rob the tree of food and the trunk becomes skinnier and skinnier, making it susceptible to wind and cold damage.
Avoid transmitting serious palm diseases by sterilizing tools before pruning each tree. Fusarium of Queen and Mexican fan palms is a fungal disease spread by infected pruning tools when the sap from an infected palm is carried on a saw blade to a healthy tree.
Solutions to disinfect pruning tools include pine oil cleaner, alcohol and denatured ethanol. A bleach solution can be used. However, bleach has been known to be corrosive.
Over pruning palms—especially Canary Island date palms—also can make them more susceptible to an insect called the palmetto weevil, Rhynchophorus cruentatus.
The palmetto weevil is typically a pest of stressed and weakened palms, but can be attracted to healthy palms by the odor the pruned frond creates. To the palmetto weevil, the cut frond odor smells just like a stressed tree.
Because of this attraction, it is recommended you wait to prune these palms in cooler months, when palmetto weevils are not as common.
See https://bit.ly/38dOKNH for a PDF with more information on palm pruning.