Palm trees are one of the plants we grow that homeowners believe are drought tolerant and basically trouble free. In fact, many of the varieties of palms we grow here in central Floridaincluding our state tree, the Sabal Palm, are trouble free and easy to maintain in most landscapes. However, few of us are able to recognize even the few minor problems these trees do have. This week I would like to go over some of the more common varieties of palms we grow and the problems associated with them. I will also describe easy to recognize symptoms of problems your trees may be displaying and how to correct these problems. Along the way, I will also point out a few problems that can not be corrected. Most of the information I give you today will enable you to look at your palms and notice immediate problems. Some of these problems may or may not require you to do something to correct the problem, so let’s get started.
Since we mentioned the Sabal palm above let us start here. Sabal palms are very common and most of these trees grow with few problems in the landscape. Unfortunately, Sabal palms are susceptible to a weevil (Rynchophorus cruetatus) that attacks the bud of the palm. The bud is the central internal growth point where all new fronds are initiated. Weevils are large beetles that are drawn to palms which are stressed from lack of nutrients or during transport of freshly dug trees. Adult female weevils can sense a trees distress and have been seen swarming trees being shipped to nurseries for resale. Weevils lay their eggs at the base of the frond and as these eggs hatch, they burrow into the heart of the palm eventually killing the tree.
You may have noticed dead palms in the past where the entire top of the tree had bent over. This is a characteristic of the after effects of weevils feeding on the bud. This feeding disrupts the flow of nutrients to the fronds and eventually the entire crown of the tree falls over. In the pest control business we call this “Deadheading” of palms. Sabal palms, Washingtonia palms, and Canary Island Date palms are most often attacked by these weevils. Because homeowners tend to remove the lower fronds of these trees through regular maintenance, make it a habit to look at the cut end of the boot of the frond. If you notice a large hole in the cut end the size of your thumb, your tree may be infested. This may be the only sign you see before your tree succumbs to this pest. Call a pest control company to spray your tree if you suspect you have these weevils.
Nutrient deficiencies are another common problem on many of our backyard palm trees. Although these problems are few and easy to correct over time, proper identification is necessary to correct these problems. If you have a Queen palm or a Cycad palm (technically not a palm) in your yard, you need to pay special attention to the new growth coming out of the top of the tree. If the new growth or fronds appearance seems necrotic or yellow in appearance and this growth appears to be crinkled or stunted you may have a problem called “Frizzle Top”.
Frizzle top is caused by a deficiency of Manganese (Mn) in the palm. Manganese deficiencies can be found in many species of palms but the most common cultivars are Queen, Cycad, Paurotis, and Royal palms. To correct this problem you need to apply Manganese sulfate which can be purchased at most local garden centers or you may use a palm tree fertilizer that contains Manganese around the base of the tree. Do not apply fertilizers by hand or directly next to the trunk but rather by using a hand held spreader. Apply three to five pounds of fertilizer with manganese around the tree making sure you stay at least two feet away from the trunk and spread fertilizer evenly up to ten feet away. For trees that are next to a water source or there is not enough room to apply a fertilizer, injection of these micro-nutrients is possible. Re-apply additional fertilizer every three months and allow at least three to four months for the tree to respond to the nutrients.
Date palms and especially the Canary Island Date Palm (or Pineapple Palm as some people like to call it) are susceptible to a Magnesium (Mg not Mn) deficiency. Symptoms of this deficiency are a yellowing of the older leaves on the palm starting from the bottom up. In severe cases, the tip ends of these fronds look necrotic in appearance. Many homeowners trim the lower fronds of these trees off because of the yellowing appearance thinking the fronds are dying or just old. As these lower fronds are removed from the tree, the tree continues to pull magnesium from the remaining fronds and directs this element to the new growth. I have seen many of these trees die from being over-pruned simply from the lack of a minor element. Apply five to seven pounds of a palm tree fertilizer containing Magnesium around the base of the tree following the guidelines above. Repeat applications every three months and allow three to four months during the growing season to correct this problem.
Potassium (K) deficiencies cause spotting and frizzling of the older lower leaves of palms, especially the Pygmy Island Date palm (Phoenixroebelenii). Sometimes these lower fronds will appear to look like they are dying or they may take on yellow, orange, or brown colored margins. Many Pygmy Date palms have been lost due to homeowners thinking the palms were diseased and then they either had the palm removed or trimmed so badly the tree could not recover. As the deficiency increases, even the new growth can become deformed. Although the Pygmy palm is usually the main host for this problem, all palms are susceptible to this deficiency. To correct this apply an 8-10-10 palm tree fertilizer with Mg around each tree in the amounts outlined above. Remember, shrubs and palms need time to absorb the nutrients applied to the soil. These nutrients must then be delivered to all parts of the plant and this process takes time to occur. You should start to see results based on the time frames listed above.
Some palms develop cracks or splits on the trunk and for some palms this is normal but vertical fissures which appear seemingly out of nowhere are usually an indication of either a lack of water or possibly too much water. I have seen some palms which were planted too deeply also develop cracks on the trunk. To control this problem homeowners should maintain adequate moisture at all times around their palms through the means of an irrigation system or by hand watering if necessary. Filling in the fissures is not necessary however; if the crack is deep enough you could spray the trunk of the palm with copper to reduce the incidence of fungus.
Another problem you may have noticed on palms is called trunk constriction. Trunk constriction of palms is caused by irregular fertilization or environmental conditions such as stresses placed on the tree due to freezes or drought conditions. Normally palm stems will increase their diameter before they elongate. If one or more of the conditions mentioned here takes place, the palm may fail to grow the same size as the previous growth cycle. This results in the trunk displaying its history of growth from years past. Many smooth-trunked palms will show several areas along the trunk which were either smaller or larger in diameter depending upon the growing conditions at that time. There is no way to correct previous year’s growth patterns.
Leaf spot diseases on palms can cause serious damage if left untreated. Sometimes, these leaf spots are hard to find or spot but there is a trick to identifying these problems early allowing you to properly treat the palm as necessary. As you inspect your palms for leaf spot diseases, you will need to cut a frond from the tree or hold the frond between yourself and a light source. Look through the palm leaf and you may notice the first signs of many of our leaf spot diseases which will appear as brown, gray, gold, or black irregular spots inside the leaf. If you notice and of these you should apply a fungicide such as copper or “Daconil” to control these diseases before you have damage or leaf loss.
Palm trees are easy to care for when you know what to look for and what to do when you identify a problem. The items I listed here are only a few of the problems I look for but should be a good starting point for you and your garden. Thanks for your time and remember, without plants we would not be here!