It is time to think about fertilizing your shrubs, trees and lawns. Our sandy soil allows nutrients to readily leach from the soil, so it is important to replenish these nutrients with fertilizer. You want to apply fertilizer while it is still warm, as the plants won’t take in the nutrients if they become dormant with the cold weather. It will be important for your plants to be strong and healthy going into the cold months of winter. Healthy plants will withstand stresses from cold weather better than underfed, unhealthy plants.
What do those numbers on the bag’s label mean? A 16-2-8 analysis on a 100-pound bag means it contains 16 pounds of nitrogen, two pounds of available phosphoric acid and eight pounds of soluble potash. The first three numbers are the primary nutrients. The first number is always nitrogen, the second phosphorus and the third is potassium. In addition to these three primary nutrients, any secondary nutrients or micronutrients are listed at the bottom of the label in a similar manner.
For lawns, a 16-2-8 or a 15-0-15 analysis would both be a good choice. Turf needs more nitrogen than do woody plants for turf density. This allows it to fight off weed invasions, tolerate foot traffic and resist attacks from insects and diseases. On the other hand, too much nitrogen can cause insect and disease problems. When the plant takes up too much nitrogen, its cell walls become thin, which makes it easier for fungi to invade. This will cause a higher than normal water need. This lush growth also attracts insects. The higher potassium content in the 15-0-15 fertilizer also helps with plant vigor, disease resistance and contributes to cold hardiness, which is why I prefer it for the fall fertilization, even though it is a little more expensive.
The state is demanding lower phosphorus rates in our fertilizers. This means the second number will be lower than you are used to buying. Turf will have a higher quality using a slowly soluble or “controlled release” material. While these fertilizers are more expensive, your lawn will be healthier if you use them.
Look for the following when purchasing your lawn fertilizer.
1. Sulfur-coated urea. Nitrogen release occurs as water moves through tiny cracks and pinholes in the sulfur coating.
2. Polymer-coated urea. Urea granules with a polymer coating. Water diffuses through the coating to dissolve urea. Nitrogen release is affected by temperature and is more rapid in summer.
3. Sulfur and polymer-coated urea. Polymer coating is added to the sulfur coated urea as protection and to slow the movement of water into the core. It combines the cost advantage of sulfur-coated urea and improved release of polymer coated urea.
Palms under three feet use a light application of 8-2-10 monthly for maximum growth. For palms over three feet, apply four times a year in early spring, late spring, summer and early fall, using a palm fertilizer at the rate of 1 pound per foot of trunk. Be sure to use the micronutrients, especially manganese and magnesium, on your palms.
For shrubs, vines and hedges, a good quality 8-2-8 analysis is recommended at a rate of 1 ½ pounds per 100 square feet. Palm fertilizer is an excellent choice for all your acid-loving plants. Four applications, in early spring, late spring, summer and early fall is what the literature recommends. Bougainvillea prefers only one annual fertilization with 6-6-6 or 8-8-8 at a rate of 1/4 pound per foot of height of bushy plant.
Citrus should be fertilized at a rate of ½ pound of 8-2-8 every six weeks for the first three years. Wait until new growth begins after planting before fertilizing. After three years, apply 1 pound per year of age of the tree with each application of citrus fertilizer in January, June and October. Reduce to ½ pound per year of age after 10 years old. Also, if you missed the January fertilization, wait until your fruit has set to fertilize. If your citrus are in bloom, it may cause the blooms to drop, resulting in a reduced crop.
It is my experience that two fertilizations, one in early spring and another in early fall, using a quality, slow-release nitrogen with micronutrients, will keep the plants healthy and growing vigorously. If you have a weak or sick plant, fertilize at optimal rates for a year or so until the plant is healthy again.
Always keep in mind that limited fertilization is much better for the environment than excessive fertilization. The Gulf of Mexico is beginning to show the results of our excessive use of fertilizer. State and local governments are beginning to address the problem of over-fertilizing by controlling the products available and educating the consumer. Sanibel is way ahead of the curve on this one. Naples is close behind, having passed an ordinance requiring all lawn maintenance companies to become certified in the Greenscapes program in order to renew their license to operate in the city. Marco Island has also adopted this same ordinance for companies doing business on the Island.
I have taken the course and think education is always a good thing. I would like to see the program also available to educate homeowners and condominium boards. They are the people demanding too many chemicals and fertilizers, in an attempt to make their property as attractive as possible. Spray companies should be targeted and trained to offer Integrated Pest Management programs to replace the blanket spray programs now offered. With new state limits on fertilizer ingredients and education for all, we can make great strides to stop the pollution flowing into our local estuaries, rivers and the Gulf of Mexico.
Marco Island is also considering a fertilizer ordinance. As I read the requirements of this proposed ordinance, I found that it is redundant, because we already have the Greenscapes program and the fertilizer label which, of course, “is the law.” I’m also not keen on restricting when you can fertilize. It is common sense that you want to stay away from fertilizing when we are experiencing heavy rains, as the fertilizer will only wash through or off the soil and into the groundwater. The Greenscapes program teaches you this. However, when people fertilize in the cold months of winter, the fertilizer can also leach into the groundwater, as the plants have become somewhat dormant and are not using this food, thus it flows unused through the soil and into the water table.
An exception to this is the use of quick-release nitrogen fertilizers to green up lawns in the dead of winter cold, when they can sometimes turn an unattractive yellow. Under this ordinance, you would be allowed to apply the slow-release fertilizer at a time it would not be used by the plants and not allowed to ever use the quick release fertilizer that would do some good for your lawn.
Fertilizing needs to be timed with Mother Nature and the plant’s needs, and there are a lot of good reasons to use it sparingly all year. New landscapes are a fine example. No offense, but I don’t think the fine art of fertilizing belongs in the hands of code enforcement employees.
So, please remember, when it comes to fertilizer, moderation is best! This will be a good thing when you see how much fertilizer is going to cost this year. Prices are up.
Eileen Ward and her husband Peter own and operate Greensward of Marco Inc., a lawn maintenance and landscaping company. Besides completing horticultural courses from the University of Florida, she has a commercial maintenance spray license and is a registered dealer in agricultural products in Florida.