It is normally not necessary to fertilize at the time of planting. Wait until the plant is somewhat established and begins to grow – say 2 months after planting. A slow-release fertilizer is safer to use than a highly soluble granular type. It also provides for proper levels of soil nutrients for a longer time. Fertilizers with soluble macronutrients disappear rapidly from the soil. Broad leafed trees can send roots out a long way from the trunk and a general broadcast of fertilizer over a large area - even beyond the drip line (edge of canopy) will be useful. Less fertilizer (<1.5 pounds per 100 square feet) more often is safer and also better for plant growth because you will lose less material due to water leaching. A layer of mulch (2 to 3 inches deep) can be very helpful in our alkaline soils to aid in solubilizing micronutrients which tend to get bound up and become unavailable to the roots.

It is not as critical to have some particular NPKMg configuration as it is just to fertilize with something. That is to say, south Florida soils have very little nutrient content and almost anything is better than nothing. I have said this for years and I still stand by it, but there are certain formulations that will greatly improve your plant growth and health. And there are a few exceptions to this maxim. High nitrogen lawn fertilizers and composted sewage sludge can cause serious problems for trees and shrubs, for example. NPKMg stands for Nitrogen, Phosphorus, Potassium and Magnesium, the "macronutrients" and are the numbers that characterize different types of fertilizer. OK, typically, only NPK are listed on fertilizer labels in the big numbers, so you have to read the fine print.

Fertilizers that contain micronutrients are preferable for routine (3-4 times per year) use - especially in the poor soils of South Florida. Many people do not realize that the typical south Florida soil is limestone or sand fill brought in by the home builder. Because of this, gardening here resembles hydroponics more than anything else, for there are essentially no nutrients in this soil. You have to add them to get plants to grow properly. You will have to experiment with the quantity, remembering that a large concentration in one spot can burn roots and foliage. You should never see little piles of dry fertilizer on the ground. Thorough scattering of fertilizer is the best protection from burning.

Speaking of burning, we once heard a landscaper tell of the method she used to fertilize with solid fertilizer. She said she watered first, then fertilized, then watered again. Do NOT do this! Fertilizers are basically a mixture of different salts. Salts are ionic compounds that disassociate (dissolve) fairly easily in water. So, if these salts land on a wet leaf - and there is no way to avoid hitting some foliage in garden plantings - it will start to dissolve right on the  surface of the leaf. A very high concentration of salt solution results and this can cause severe burning. The best thing to do is to fertilize when leaves are dry, then water thoroughly, wetting down the foliage to wash off any solid fertilizer. If you see residual fertilizer on the leaves, be sure to rinse it all off right away. Be especially careful about those areas found in many tropical plants where large upright leaves emerge from a stalk, as these can hold large amounts of fertilizer like little cups.

We have used a variety of fertilizers with some or all of the following minor elements: manganese, boron, copper, zinc, sulfur, iron and molybdenum. "Palm Special" fertilizers usually have a higher proportion of potassium and micronutrients which many palms require. Banana fertilizers have high potassium content. There are also specialty fertilizers available for plants that require acid soil, such as gardenias. These fertilizers are generally named after the plant they are designed for. The ideal fertilizer for south Florida soils would contain all the micronutrients plus NPKMg in a ratio of 2:1:3:1 such as 8-4-12-4.

 Finally! Almost all fertilizer formulations you can buy have macronutrients in water-soluble formulations only. This means that the nutrients are quickly released and pretty much just go into the aquifer with the first good rain. So what can you do? Here is some good news: Atlantic Fertilizer now has a 8-2-12-4 sulfur-coated slow-release fertilizer available which also contains manganese, boron, copper, zinc and iron. We promised we would tell when this occurred. It is called "New Improved Palm Special #9836". Atlantic Fertilizer (Also referred to as AFEC) is located in Homestead, Florida at 18375 SW 260 Street. It is just east of the Brooks packing plant which you can see from Redland Road. Atlantic Fertilizer looks rather industrial - like an outfit that would only sell wholesale, but this is not the case - they do sell to anyone who walks into their front office. Don't be shy; you can buy just one fifty pound bag if you like. Be aware that it will cost significantly more than the quick-release fertilizers, though. Also, Lesco offers a sulfur-coated (slow-release) macronutrients (Lesco 8-2-10-3). Lesco brand fertilizers are now being carried by Home Depot.

Many plants, especially tropicals like heliconias, will benefit from a foliar application of epsom salts (magnesium sulfate), especially at the start of the growing season. We use 1 tablespoon horticultural epsom salts and one of potassium nitrate per gallon of water and drench the foliage once every two weeks or so after spring cleanup until the plants start to green up nicely.

You will notice that every fertilizer we use has minors (also called micronutrients). These aren't needed in huge quantities but they are needed, or deficiency symptoms will develop. We also add minor elements to our container plants. Micronutrients are manganese, iron, zinc, sulfur and boron.

In this area it is also recommended to use a micronutrient foliar spray twice a year. Fruit trees especially will benefit from this as well as the application of chelated iron (such as Sequestrene 138 or Microlific Iron EDDHA) dissolved in water and applied to the soil as a spray two or three times a year. Non-chelated commercial iron additives do not work in our alkaline soil.

We do not (in zone 10) fertilize in-ground plants between the beginning of November until some time in March whenever possible. (Signs of any deficiency will over-rule this policy.) That way, new leaf growth initiated by the administration of nitrogen will not likely be present and susceptible to possible extreme cold snaps during this time. The best approach is to fertilize with a balanced, slow-release fertilizer over the entire landscape, lawns included, in March, June and September.

One final note: Turf fertilizers with high nitrogen content can cause problems with trees and shrubs because the high nitrogen encourages quick growth and often there are not enough of the other nutrients available - particularly potassium and particularly in palms - to take part in this growth. So, what you do is create an artificial potassium deficiency by adding too much nitrogen. Recent research at the University of Florida has found that composted sewage products bind up micronutrients and prevents them being absorbed by plants. So these are to be avoided in your fertilizer program especially as soil amendments during planting.