Print

Email story

Comment

Email editor

Home

Garden: Prepare a smorgasbord for your hungry palms

Without regular, balanced feedings, fronds may fade. But for palms, diet usually cures what diet causes.

By YVONNE SWANSON
Published March 25, 2006

If your palms could talk, they'd shout, "Feed me!" Of all plants in the Florida landscape, palms tend to be the most nutritionally needy and quick to show their distress.

Their fronds seem to turn yellow practically overnight or their new growth shrivels up into a yellow "frizzle top." Palms always seem to be lacking some nutrient, most likely nitrogen, potassium, magnesium or manganese. Nutritional products are available to treat each of these common deficiencies, but figuring out what's lacking and what's needed can be a big challenge. What's more, treating one deficiency sometimes leads to another nutritional void.

The easiest way to keep palms green and thriving year-round is to feed them with a complete, slow-release granular fertilizer formulated especially for palms, often labeled as a "palm special." It should include equal percentages of nitrogen (N) and potassium (K), along with additional magnesium (Mg) and a mixture of micronutrients. Horticulture experts recommend feeding palms at least four times a year, ideally in February/March, May/June, August/September and November/December.

There are numerous palm fertilizers to choose from, but it's important to select one that includes soluble nutrients that will break down quickly after application. If the ingredients are insoluble, it can take three to four months before the palm digests its feeding.

Mature palms should be fed 5 to 8 pounds at each application; palms under 8 feet tall can have 2 to 5 pounds; and newly planted trees get one-half to 2 pounds, depending on size. Spread the fertilizer about 3 feet away from the center of the trunk or under the canopy of the palm so that new roots won't be injured.

But what if your palm is showing signs of nutritional stress and needs targeted treatment? It's difficult to diagnose specific deficiencies because their symptoms can overlap, and treatment may in some cases take years to rejuvenate starving palms. Once foliage is damaged by deficiencies, it must be replaced by new, healthy growth. With slow-growing palms, that can mean just one new frond a month during warm season and even fewer in winter.

The easiest problem to treat is nitrogen deficiency, which turns the entire plant light green. You can easily darken the plant's color by applying any nitrogen fertilizer to the soil or spraying it onto the foliage.

The most widespread, serious disorder in Florida palms is potassium deficiency, which causes translucent yellow, orange or brown spots, first on older fronds, then on new growth as the deficiency becomes more severe. Experts recommend a quarterly use of 3 to 8 pounds of slow-release potassium sulfate per palm, plus half as much magnesium sulfate to prevent an imbalance.

When the palm's new growth is partly yellow and small with new fronds that appear frizzled, the problem is manganese deficiency. All palms are susceptible, especially queen, paurotis and royal palms, as well as most palms that grow in alkaline soil. The condition, which can be fatal, is usually treated with a manganese sulfate product at the rate of one-half to 2 pounds per plant.

Magnesium deficiency affects older fronds, causing light yellowing at the edges while the center band stays green. Most palms are at risk, especially date palms, but the disorder is rarely fatal. Treatment requires quarterly applications of magnesium sulfate and potassium sulfate at the rate of 2 to 4 pounds per palm to correct the problem and prevent a magnesium-potassium imbalance.

Horticulture agents will diagnose your palm's deficiency if you take a frond to your county extension office. You can also visit the University of Florida's Plant Nutrient Deficiency Symptom Database at http://hort.ifas.ufl.edu/nutdef/decision.htm. The site allows you to diagnose your plant's problem by answering a series of questions. Closeup photos show the symptoms of deficiencies.

Yvonne Swanson is a freelance writer in St. Petersburg and a master gardener for Pinellas County.

[Last modified March 24, 2006, 12:10:36]