Palm Care: Part 1

Three Reasons Why You Should Not Over Prune Your Palms

You can’t drive very far in Florida without seeing a palm tree. It is an important piece of the Florida identity, after all the sable palm is our state tree. They provide a great habitats for several animals, insects, and even other plants. Their flowers and berries provide important food sources for bees, pollinators, all sorts of birds, and habitat for bats. As long as it is the right plant, in the right place, palms can be a great choice in a home landscape, but will need a moderate amount of care. For this blog post, we will be talking about the dangers of over-pruning palms. Knowing how much to prune can ensure that your palms stay healthy for years to come.

Palm Crown Cross Section — A cross section of growing tip of a Queen Palm. [Click photo to enlarge] Photo Credit: T. K. Broschat, UF/IFAS

Quick Word on Palm Biology

There are so many different topics of palm biology (including rather or not palms are actually trees, which is a topic for another time) that would make this blog exceptionally long. So, to keep on topic, let’s talk about the area of growth. A large majority of palms have one trunk and all growth occurs at the tip. The photo to the right show a cross section of the crown (top of the plam) of a Queen Palm (this picture was taken from the EDIS Document “Palm Morphology and Anatomy” a link to this document can be found in the links at the bottom of this blog).

Using the picture as a reference, the dark brown area of the cross-section is the crownshaft where the mature leaves are attached to the tree. You can see the development of a flower starting on the left side. Now comes the important section. In the middle you have the primordial leaves. These form the leaf-spear and unfold into a new leaf. In this cross-section you can see several that are in development. The stem is what will ultimately become the trunk. In between the stem and the primordial leaves is the meristem. This is a thin line of cells, those on the bottom form the stem and those on top form the fronds. This is the most important part and it is normally referred to as the heart of the palm. If this area is damaged, your palm will more than likely die.

Reason # 1: Older Fronds protect the meristem (growing tip)

We’ve learned many lessons from past hurricanes. Chief among these is that removing palm fronds (the correct term for palm leaves) before a storm or for storm season is very detrimental to the palm. During major storms, there is a lot of drag put on the fronds of the palm. Remember the newer the frond, the closer the attachment is to the meristem. In a full crown, the wind is buffered by the outer fronds. If these bend, break or tear off, it affects the palm less and lower the amount stress is put on newer fronds. In a palm that has been “hurricane cut” all the old fronds are removed and only the newest fronds remain (please see photo 2 for an example). These fronds have not had a chance to harden enough to protect the growing tip. This can lead to the entire crownshaft being snapped off killing the palm.

A group of Sable palms that have been over pruned — An example of Sable Palms that have been over pruned at the beginning of hurricane season. [Click photo to enlarge] Photo Credit: Michael Orfanedes

Think of the crownshaft as an onion. On the outside of an onion you have the older leaves that have dried up. The same can be said about a palm, outer leaves are the oldest and as they age they are easily removed. As you proceed inward the leaves become younger, thicker, and better attached to the center. The outer layer comes off pretty easily but as you progress it becomes harder to peel the leaves off without damaging the area of growth (the center). On a palm, when a hurricane comes, the wind picks up and peal off the thin outer layer (fronds). Then the storm strengthens enough to remove the next layer (also fairly thin). As the storm progresses the layers continue to peal off, but usually a healthy palm will outlast the storm. However, if all the outer layers (fronds) are already removed when a major storm happens, there is no protection for the newer leaves. The winds strip these leaves until the last leaf takes the meristem with it or exposes it to the elements and it is sheared off. Therefore, keeping the crown as full as possible makes a more hurricane resilient palm.

Reason # 2: Over Pruning Can Exacerbate Nutrient Deficiencies

Nutrient deficiencies are common in most palms in the Florida landscape. The most

A nutrient deficient Phoenix palm — Many palms in the Florida Landscape are nutrient deficient (yellow older leaves and poorly developed new leaves) which can be worsened by heavy pruning.

common deficiency of palms is potassium. What does this have to do with pruning? Well, several nutrients such as potassium are movable elements. If the plant is deficient enough it will take these nutrients from the older frond to use in the growth of newer fronds. As this happens the edge of the older fronds turns yellow then brown. Often the leaflets or outer edge of the palm frond may be dead but the center is still green. Unless the center frond is brown, it is not good to remove it. This is because there are still nutrients that can still be pulled from and used elsewhere. You can tell a naturally dying frond from one that is exhibiting a nutrient deficiency by the speed at which it dies. An old frond will turn a bronze color quickly and then die. One with a nutrient deficiency will be much slower to die.

Severe nutrient deficiencies can lead to the death of a palm if not treated. If your palm is exhibiting a nutrient deficiency you should utilize a fertilizer with the numbers 8-2-12 +4 on the bag. Also depending on the size of your palm, you may need to fertilize most of your lawn as palm roots extend a long way from the trunk. For more information see the document linked below called “Nutrient Deficiencies of Landscape and Field-grown Palms in Florida.”

Reason # 3: Over pruning opens the Palm Up to Pests and Diseases

The final reason not to over prune is because it exposes the palm’s healthy tissue and causes stress. Just like on people, the more cuts that are done to a palm the greater the chances of infection. More than likely this can be from a fungus or bacteria. The most common reason for infection is improper sanitation of tools. A pole saw used to cut one palm with bud rot, a highly detrimental fungus, can quickly spread to any palms pruned next. Therefore sanitation of tools is really important. Next, removing a large number of fronds can cause the palm to become come stressed. A stress palm releases a pheromone that attracts insects like the Palmetto weevil that can decimate a palm very quickly. Other major stressors that can compound this are nutrient deficiencies and drought.

It wasn’t until the crown was excavated that these were found. Grubs of Palm Weevils which ate the growth tip. Photo By Eric J.

Unfortunately the palm experienced Crown Collapse and died. Photo By Eric J.

This photo of a Phoenix palm was submitted for diagnosis. The droopy leaves pointed to either a nutrient deficiency or water issues. Photo By Eric J.

Conclusion

Over pruning, palms can lead to several different scenarios often leading to the death of the palm. Leaving palms for as long as possible can not only keep your palm healthy it can provide important habitats for birds and especially bats. Keeping your palms as healthy as possible will ensure a long life. There are some guidelines that you can follow if you want clean up your palm canopy.

Cut off only dead (completely brown) palm fronds.
If you need to cut more, imagine that the canopy is a clock where the center is where the fronds all meet the trunk. Any fronds that are below 3 and 9 you can remove.
Clean all tools between trees to prevent contamination. For more information on cleaning your tools please visit Disinfecting Your Garden Tools
Put your palm on a regular fertilizer schedule.