I attended (and spoke briefly) at Palm Disease Update presented by Dr. Monica Elliot, Professor of Plant Pathology and Associate Center Director of the Ft. Lauderdale Research & Education Center of the University of Florida. While Dr. Elliot covered several topics, I was most interested in Texas Phoenix Palm Disease, which is killing Cabbage Palms in Manatee County (ironically around Palmetto). For more on this phenomenon, see an earlier blog. But I ended up with new insights about why pruning cabbage palms is ill advised.
Here's my take: In my opinion, the only fronds one should remove are ones that are completely dead, the color of a manila envelope. And I'm not even sure why anyone would spend time and energy doing that.But removing green or yellow fronds has several negative effects.
1) The palm tree is able to remove nutrients from the aging frond. Removal before they are completely dead deprives the palm of these nutrients.
2) The dying fronds can serve as barometers that let plant specialists interpret nutritional deficiencies or disease. Removing these fronds can complicate diagnosis.
3) In addition, taking fronds with still-living tissue wounds the plant. Any wound is a potential entry point for insects or disease. This problem is magnified in palms, which lack the wound healing capacity of dicots.
4) Removing green fronds reduces the photosynthetic capacity of the plant. Few people would contemplate taking a third of the photosynthetic surfaces (leaves) from something like an oak, but many don't bat an eye about taking ten green fronds from a cabbage palm. This reduced capacity weakens the palm and can cause pencil-neck, a narrowing of the trunk.
These first four points all contribute to weakening the tree, the opposite effect most people want in a home landscape.
5) Some overprune to what has been called the "hurricane cut". There is no rational reason for this. If you had a hundred species of trees on your property, the last tree that might need pruning to survive a hurricane is the cabbage palm. And Dr. Elliot suggested there may be evidence that "hurricane cut" actually makes palms more vulnerable. That make some sense because the growing tip "sword frond" is more vulnerable after severe pruning.
6) Finally, it takes only seconds to pick a fallen frond off the ground. Just about anyone can do it. Removing live fronds requires far more time, the use of sharp instruments and frequently, ladders. All this increases costs and risks. Landscapers must be laughing all the way to the bank, because they are charging top dollar for dangerous work that is completely unnecessary. Cabbage palms are self pruning. The fronds fall off when they fall off and in the meantime contribute to the full spherical head that typifies the species. And who wants to be calling an insurance agent or making a trip to the emergency room to solve a problem that could have been avoided with the simple application of patience and gravity?
The photo on the right shows a young over-pruned palm. (My version shows the image with strange color.)The circles identify 21 fronds with some green left in them. Let's assume there are only 4 comparable cut fronds on the other side that we cant see, for a total of 25 missing leaves. At the top we see only a few left, maybe five. That means 5/6 (83%) of all the leaves have been removed -- a devastating loss for just about any plant.
Check out some of these other sources.
If you don't love your cabbage palms, keep pruning. Eventually they will grow to reflect your antipathy.
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Jono