Palms Require Special Care

by Terry B. DelValle

special  to the Florida Times Union for 8/20/05

 

Have you noticed that our landscape look is changing?  Palms are becoming a more dominant feature along roadways and in the landscape.  And they're not the standard cold hardy palms like sabal, pindo and Canary Island Date palms.  Add to the list date palm, queen palm, pygmy date palm, mule palm and others.   

Winters have been mild and some of these plants have not been tested as to their cold tolerance in our area.  Many of the palms are brought in as mature specimens from very arid climates.  With the drastic increase in rainfall and humidity on the east coast, some older specimens have difficulty adapting.  The mule palm (Xbutiagrus nobannandii) is an interesting hybrid that occurred by accident in Florida.  It is a cross between Butia capitata (Pindo palm) and Syagrus romanzoffiana (Queen palm).  Because of the cross, it should be more cold-hardy than the traditional queen palm but still has the tropical look of the coconut palm, a close relative.   

 

Planting Tips: One of the most common reasons for loosing palms in the landscape is improper planting.  Often palms are planted at varying depths to achieve a uniform height.  We often receive telephone calls from people distressed over newly planted palms with few or no leaves.  This is not a mistake by the installer but is actually a technique to increase the palms survival rate.  To minimize water loss, half or more of the older leaves should be removed at the time of digging.  The remaining leaves are tied up around the bud with a biodegradable twine.  Research has shown that cabbage palms, Sabal palmetto, are the exception.  They have a greater chance of survival if all leaves are removed at digging because they tend to loose all their roots at transplanting.  In addition to removing the leaves, palms have a higher chance of survival if planted in spring to early summer due to warmer soil temperatures.

When palms are dug from the wild, they are often different heights.  To compensate for this and to create the illusion of palms of matching heights in a landscape, some installers plant them at varying depths.  Planting too deep leads to root suffocation, nutrition problems, and root diseases.   Do not plant palms any deeper than they were originally grown.

Once installed, keep the root ball and surrounding area moist, but not too wet, for the first 4 to 6 months.  For expensive palms, like the date palm, drench the root zone 2 to 4 times during the first few months with a soil fungicide product like Subdue.  Three to four months after transplanting, apply a slow release "palm special" granular fertilizer at 1/3 the recommended rate as a band at the edge of the root ball, not against the trunk.

Newly planted palms are considered "stressed".  Stressed palms attract palmetto weevils that tunnel into the bud, destroying the palm.  Palmetto weevils most commonly attack cabbage palms and Canary Island date palms but have been reported on other palms.  Once the palm has this weevil, the palm will die, so control must be done preventatively.  Spray the bud at the time of installation and several weeks later with an insecticide like permethrin.  The best control is to promote a healthy tree by fertilizing and watering appropriately.

Keep turf away from the base of palms.  Instead, apply a small area of mulch and pull the mulch 2" to 3" away from the trunk base.  The main reason for this is to prevent damage to trunks from line trimmers and mowers.

Pruning:  Many landscapers who maintain palms have a tendency to over prune and give palms a "hurricane cut".  Remove palm leaves if they are completely dead (brown).            Older palm leaves are often removed because they are showing nutrient deficiencies and are off-color.  Some nutrients are transferred from old to new leaves.  Removal of these leaves will make the nutrient deficiency worse and results in a condition referred to as "pencil top" (trunk narrows just below fronds).

Troubleshooting: 

Potassium and magnesium deficiencies are two common problems in our area.   Potassium leaches quickly from Florida soils and deficiencies can be fatal to palms.  Symptoms begin as translucent yellow-orange or brown spots, marginal burn, or frizzling of the oldest leaves.  Problems show up first at the leaf tips and are less obvious at the leaf base.  Eventually entire leaves appear burnt and withered in appearance.  To prevent, use a fertilizer with sulfur-coated potassium sulfate but be sure to include magnesium in the application to avoid an imbalance.

Magnesium deficiency is common on Canary Island date palms, Phoenix canariensis, is rarely fatal but is unsightly.  Classic symptoms are a broad, lemon-yellow band along the margin of older leaves with a distinct green center along the midrib of the leaf.  To prevent, make sure magnesium is part of the fertilizer program.  Affected leaves will not resume the green color once fertilizer is applied.

Several insect and disease problems affect palms.  One that we are seeing a lot of due to wet weather is pestalotiopsis leaf spot.  This leaf spot affects a number of palms but is more of a problem on date palms.  Control with sprays of copper based fungicides and keep irrigation water from hitting leaves.

Extension information and services are available to all individuals regardless of race, color, sex or national origin.  The information herein is for educational purposes only.