Don't trim your palms! Or at least don't trim until the fronds are brown.
A question that we are frequently asked is whether or not palms in the landscape should be trimmed. The answer in almost all cases is NO! There are several reasons why this is not a good practice.
1. Your palms have stored energy inside their fronds. Unless the frond is completely brown, there are stored carbohydrates (sugars) that the palm is expecting to utilize. As each frond changes from green to yellow to brown, the palm is withdrawing the stored nutrition inside the frond. The palm then uses those sugars to produce new growth. Removing even a few green fronds from a healthy palm will induce a nutrient deficiency and in some cases can be fatal. Similarly, removing chlorotic (yellow) fronds will create a vicious cycle and force the palm into a continually malnourished state, even if the deficiency has been corrected by proper fertilizer application. Removal of green fronds is an unnatural act and forces a palm to use its stored nutrition before it normally would. Think of each frond as a dinner plate with food on it. Removing plates of food will cause the palm to become hungry.
2. The palm frond is the palm's sole source of energy. Palms, like nearly every plant, rely on photosynthesis to survive. Photosynthesis is the process of converting light into sugars, which are then stored in the fronds. Removing fronds prematurely reduces the photosynthetic capacity of the palm and therefore slows its growth. Unlike hardwood trees that can grow multiple leaves from multiple branches, palms can only create one frond at a time.
3. Trimming can spread diseases. When living fronds are removed from a palm, living tissue is cut. Palms have a circulatory system and sugars and water are constantly moving throughout the palm. If the pruning equipment has been exposed to disease from an infected palm, it is highly likely to be transmitted to a healthy palm when living fronds are removed.
Removing healthy fronds makes palms LESS storm tolerant. Many people have their palms trimmed near the start of hurricane season. This is not a good practice as stated previously, as palms store energy in their healthy fronds. Over pruning leaves the fewer remaining fronds more susceptible to wind damage. Healthy palms with full canopies are much more tolerant of hurricane force winds and are able to recover more quickly. After a hurricane, leaving cracked, hanging green fronds on the palm is a good practice as well. In the months after Hurricane Wilma in 2005, we observed a quicker recovery and less death on palms that were left alone rather than heavily pruned.
Palms that are fertilized properly at consistent intervals will remain green from top to bottom and will not prematurely yellow. Palms with a crownhsaft are self-cleaning and will drop their fronds naturally when they are finished using the energy stored inside. Palms that do not drop their fronds naturally are finished using the stored energy when each frond browns completely.
In conclusion, with regards to removing fronds from palms, the less you do, the better.