What's ailing South Florida's palms? The diagnoses vary

Coconut palms nearly everywhere you turn are clutching hayfields of lower brown or yellowish fronds, made more conspicuous by the new greens of spring adorning the mahoganies, seagrapes and pigeon plums.

The tail-end of the dry season is when palms look their worst and are ready for some trimming, fertilizing and water.

Mix in a vast amount of transplant shock, hunger, royal palm bugs, patches of lethal yellowing disease and winter blahs, and you get the general impression that palms here are feeling rather poorly.

It's no wonder palm lovers, such as Key Biscayner Joan Gill Blank, are concerned.

Last week, Blank phoned Don Evans, director of horticulture at Fairchild Tropical Garden, asking for an expert appraisal of palms that seem to be woefully under the weather.

Blank prowled the Key, turning each corner with increasing alarm by what she saw. When Evans retraced the route with her, he was able to allay most of her fears and confirm some of the worst.

Winter -- which failed to wallop us with freezing but nonetheless doled out weeks of chilly -- also chilled the palms. Blank said that Key Biscayne, surrounded by the warming Gulf Stream and bay waters, stays a good two degrees warmer than the mainland, but two degrees didn't help much this year. Coconuts particularly, said Evans, are hot-blooded tropicals that turn downright wimpish in winter, showing brown fronds as a result.
Damage from cold

Most of the coconuts that gave Blank a fright are showing signs of cold damage: brown lower fronds that stay attached to the crown. Coconuts all over South Florida are looking this way.

In a few cases, however, the flagging fronds were symptoms of lethal yellowing, and in still others, yellowing fronds were gasping in the face of starvation.

Certain coconuts, Christmas and date palms around South Florida still get lethal yellowing disease, a fatal illness spread by tiny insects called leaf-hoppers, which spend a portion of their life cycle in St. Augustine grass. When sick, Evans said, the lower fronds quickly collapse. The disease progresses fairly quickly from outer fronds to the inner, newest spear.

On coconuts with lethal yellowing, the flower stalks discolor and drop flowers; coconuts abort before becoming fully formed.

Golden Malayan dwarf coconuts (somewhat resistant to lethal yellowing, but still able to contract the disease) have naturally yellow coconuts and petioles, which are the leaf stems. This gives them a yellow cast. If homeowners fail to fertilize these palms, the cast takes on a solar glow. In these cases, Evans said, the coconuts need ``some micronutrients and plain old balanced fertilizer.''
Royals suited to swamp

``Unless people actively care for their plants, they'll look pretty poor here,'' he said, explaining that sandy soil is a poor medium for retaining nutrients plants need. Rocky and sandy soils of the mainland are equally poor hosts for many palms; fertilizer is a must if they are to flourish.

Royal palms on the Key with that limp look are suffering from wind damage, Evans said. ``The palms aren't very suited to beachfront culture,'' he added.

And they find the transition from nursery to roadside a hard one to make. Royals grow naturally in the sloughs and strands of the Everglades. They are swamp palms, which grow majestic in the organic peat, far away from coastal winds. Nurserymen grow them in fields of moist muck.

When transplanted to new housing developments or to highway roadsides and medians, such as those along Kendall Drive, they go into shock and their fronds turn brown. With summer's rainy season not far away, new fronds will emerge one at a time every four to six weeks, and will help these palms look better.

More-established royals, such as those along Miami's Metrorail, are showing some brown lower fronds with a frazzled look. These are old fronds that were sucked dry of juices last year by the royal palm bug. This is the time of year when the minute insects are active, wedging into the unopened spears at the top of the palm. When the fronds open, they have a yellowish cast and gradually turn brown, sinking lower in the crown as the palm grows.

Royals with robust trunks that gradually taper into skinny, pencil-like tops are suffering from hunger and thirst, Evans said.
Starving trees

Date palms in South Florida can develop yellow lower fronds, signaling a need for magnesium, one of the micronutrients they require.

Queen palms that Blank worried about on Key Biscayne have increasingly smaller fronds, looking as if an egg beater had been taken to them -- a condition aptly called ``frizzle top'' that, if unchecked, can kill the palms. This is another starvation symptom, an especially loud bleating from the palm that it needs manganese.

So what Evans prescribed for Key Biscayne's winter-withered palms goes for you mainlanders, too: Remove the brown, cold-damaged fronds and apply fertilizer. Because palms need plenty of potassium and micronutrients such as iron, manganese and magnesium, apply fertilizer especially formulated for them, such as 12-4-12-4.

And if you want to plant palms, ask your nurseryman to help you select those resistant to lethal yellowing, including Mapan coconuts, foxtail, thatch palms and a long list of others. More susceptible are Jamaica tall coconuts; seeds brought from Jamaica that are not certified, Christmas palms and Pritchardia palms.