Royal Palm
Royal palm is aptly named for its majestic presence in the landscape. This palm is most suited for South Florida, where it is native to the region. It works nicely as a specimen plant and is often found lining streets and parks.
Characteristics
Royal palm (Roystonea regia) grows very tall and commanding in size, reaching 50 to 70 feet and spreading 20 to 25 feet wide. Its large stature can make it difficult to grow on smaller properties, especially since it will self-prune and naturally drop its very heavy dying leaves once a month. This is common with palms that have a “crownshaft,” which is a five-foot region at the top of the tree below the fronds where tightly overlapping leaves form a smooth surface on the trunk. Each royal palm frond is about 10-15 feet long and weighs upwards of 50 pounds, posing a hazard if it lands on people or property. If you are planting a royal palm, be strategic about where you plant it to reduce risks.
Royal palm is quite sturdy and can withstand hurricane-force winds, which makes it ideal for South Florida. The palm produces tiny cream-colored flowers that are followed by dark red to black fruits. Since the fruits are popular with birds, their seeds are widely dispersed. These fruits may be slippery and messy, so as mentioned, it’s good to consider where you plant this Florida native.
Planting and Care
This mighty palm can survive cold temperatures to about 28°F, which means it can grow as far north as USDA Hardiness Zone 10A. It is moderately tolerant of salt spray but cannot handle high saltwater concentrations near its roots. This palm can surprisingly grow in both wet and dry soil conditions.
If you wish to plant a royal palm seed, first you want to put on some rubber gloves, because the fruit pulp is highly irritating to skin. Then you can remove the fleshy fruit pulp and rinse the seed. Sow the seed in well-drained, moist potting soil and keep it warm. The seeds may germinate 5-8 months after planting.
If you don’t have that kind of patience, you can purchase the palm and transplant it into your landscape. Holes in the landscape for the container-grown palms should be roughly twice the diameter of the container. Always plant the palm so that the top of the root ball is one inch below the surface of the soil.
Nutrient Deficiences
Royal palm is prone to certain nutrient deficiencies: potassium (K), manganese (Mn) and boron (B).
The leaves of a palm deficient in potassium will turn brown on the edges (leaflet tip necrosis) and will develop a crispy/curling texture (frizzling). It can also cause premature loss of leaves or a tapering of the trunk. Severe cases will kill the tree.
Manganese deficiency can also cause frizzling, but the symptoms occur on new leaves, while potassium deficiency affects older leaves. Severe cases may cause the tree to die if it is not treated with manganese sulfate.
Boron deficiency usually causes new leaves to be stunted or distorted, and in some cases can cause the tree to become deformed. A tree with the entire top of the palm growing sideways is likely caused by boron deficiency. In rare cases, this condition can also be fatal.
With attention to detail, you can learn to identify these problems with your tree. To combat nutrient deficiencies, you may use a controlled-release fertilizer with an analysis of 8-2-12-4 Mg (or 8-0-12-4 Mg) plus micronutrients. Contact your local UF/IFAS Extension office for more fertilizing specifications for royal palm.
Pests and Diseases
Royal palm does not have very many serious insect pests, but one common critter is the royal palm bug (Xylastodoris luteolus). The infestation symptoms mimic that of potassium and manganese deficiencies, however the leaves are frizzled throughout their whole length, rather than just on the tips. Insecticidal control is the only known reliable method for controlling the royal palm bug in Florida.
Royal palm is also affected by a couple diseases, although it is relatively disease resistant. Ganoderma butt rot, caused by the fungus Ganoderma zonatum, infects the interior bottom three feet of the trunk. It will cause wilting and sometimes a fruiting structure of the fungus called a conk will appear on the outside of the lower trunk. This is a warning sign that the tree is at risk of falling and should be immediately removed. Unfortunately, it is unknown what conditions cause the disease to develop and there are no cultural or chemical controls for preventing or curing the disease.
Thielaviopsis trunk rot is another disease that can infect royal palm. In order to infect the tree, the fungus requires a wound in the upper portion of the trunk, such as from pulling or pruning leaves off. This causes a rotting of the entire crown, which can fall off without warning. The moral of the story is: do not remove leaves or cause other wounds to the trunk, as this can unleash a devastating fungus. There are no methods for curing the disease once it has taken hold.
Royal palm is a uniquely South Florida plant that gives a tropical feel to the landscape. Diligence should be taken to identify and diagnose any issues with your royal palm. This otherwise very stately tree is guaranteed to create a classic “Sunshine State” feel to your property.
