Q: We’ve had a bad cold snap and more coming. How do I know if I have damage on my palm trees?
Answer: Palm species vary in their cold hardiness, so it is important to know which palms are the right plant for your zone. One way to determine that is to review a copy of the “Florida-Friendly Landscaping Guide to Plant Selection and Landscape Design.” You can access this guide at http://fyn.ifas.ufl.edu/pdf/FYN_Plant_Selection_Guide_v090110.pdf.
Timothy K. Broschat of the University of Florida wrote “Cold Damage on Palms,” which provides a wealth of information on this topic. You can access this publication at http://edis.ifas.ufl.edu/mg318, and the information that follows is from this article.
There are three types of cold damage to palms: chilling injury, frost and a hard freeze. Chilling injury can happen when a tropical palm species is acclimated to a certain nighttime temperature and then the temperature drops significantly. The damage is noticeable within a few days of the cool/cold weather and includes discolored leaflets and dead tissue (necrosis). Younger leaves may not suffer damage, and older leaves may have significant damage.
Frost damage occurs when the leaf surface temperatures drop to 32 degrees or lower but the air temperature is several degrees higher, which happens on clear, calm nights without wind or clouds in open areas where the palm is not protected.
A hard freeze occurs when air and plant surface temps drop below 32 degrees due to cooling winds. The least cold-hardy part of the palm is the base of the leaf spear, which may be able to be pulled out of the palm with minimal effort. Although many people want to prune right after a cold-weather event, don’t remove damaged palm leaves until the danger of more cold weather is behind you. Even dead leaves provide some insulative value to the palm meristem.
You may notice that the new leaves appear to have shorter leaf tips or some tissue death mid-leaf. The damage could be due to the cold or a micronutrient deficiency.
For information on treatment of cold damaged palms, fertilization and to view photos of potential damage and micronutrient deficiencies, please review Broschat’s publication.
Lynn Barber is the Florida Yards and Neighborhoods agent at Hillsborough Extension. Reach her at BarberL@hillsborough county.org.