Establishing a good fertilizer management plan
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Last month we learned some of the basics of fertilizer composition and how important it is to "read before you feed." Now that we are entering the growing season (with less than 2 months before the fertilizer blackout that extends from June 1 through Sept. 30), it is a good time to review or establish your fertilizer management plan to ensure that you meet your nutrient goals in the garden.
The various plants in your landscape will have distinct fertilizer requirements, and your plants will need a different fertilizer than your turfgrass. Your first consideration should be to have your soil tested to see which nutrients are present and what elements may be lacking. You can obtain a soil sample kit at your local county Extension office (https://sfyl.ifas.ufl.edu/find-your-local-office/).
Plants also have different requirements for the appropriate amount of fertilizer you use; container-grown plants must be carefully monitored for a build-up of salts from over-fertilization that can cause stunted growth, leaf browning or even death. Likewise in the landscape, over-fertilization can burn plants, trigger excessive growth or even aggravate pest problems.
Slow-release fertilizers are generally your best option to help avoid issues with applying too much fertilizer, as well as preventing nutrients leaching into the water supply. And as we learned last month, it is critical that you thoroughly read the label and follow all directions when applying any type of fertilizer.
You should always use caution when applying fertilizers; the Florida-Friendly Landscaping fertilizer recommendations provide valuable guidance to help avoid environmental harm to our waterways and water systems.
Do not fertilize when heavy rain is expected.
Leave a 10-foot-wide no-fertilizer zone around or along water bodies.
Established trees and shrubs (more than 3 years old) do not generally need supplemental fertilizer.
Fertilizer type depends on soil conditions; nutritional deficiencies can develop due to conditions such as high pH, compacted soils or damaged and diseased root systems. This is why a soil test through your local county Extension Office is so highly recommended!
"Fertilize Appropriately" is the third principle of Florida-Friendly Landscaping. Depending on the age of your plants and the soil requirements, it may not be necessary to fertilize, but "Weed and Feed" fertilizers are NOT recommended for a Florida-Friendly Landscape. These "Weed and Feed" products contain fertilizer and weed killers, or pre-emergent herbicides, and are billed as a time saving way to fertilize your landscape while killing weeds. The problem is that most pre-emergent herbicides should be applied much earlier in the year than fertilizer and applying either product at the wrong time of year renders them less effective.
"Weed and Feed" fertilizers can actually injure trees and shrubs because their root systems can extend far beyond the plant's drip line (the area located directly under the outer circumference of the branches) out into your lawn area; if the plants absorb the “weed” portion of the formula, it can be harmful. The herbicides contained in these products can also harm lawns if applied when temperatures are above 90 degrees for three consecutive days, and we all know that these high temperatures are not infrequent in Florida during the spring!
You may now be wondering which fertilizer will be appropriate for which plant? Slow-release fertilizers are ideal for our soil conditions and are both economical and easy to use. Here are a few guidelines to consider:
a balanced all-purpose fertilizer such as 10-10-10 or 20-20-20 is beneficial for fertilizing green shrubs, flowering shrubs, annuals or container plants.
Palms have specific fertilizer requirements, and the University of Florida recommends 8-2-12 +4Mg fertilizer for palms. Make sure the sources of N (first number), K (third number) and Mg (an important micronutrient) are 100% control released for maximum effectiveness.
Most vegetables benefit from a balanced 6-6-6 or 10-10-10 fertilizer.
The University of Florida recommends 8-8-8- fertilizer with other macro and micronutrients for citrus in the home landscape.
Slow-release granular fertilizer should be spread around the base of a plant or tree at the drip line, not just around the trunk. Remember to water your plants well after fertilizing; if you use a liquid fertilizer product, water the plant well and allow an hour for the plant to absorb the water, then apply the liquid around the base of the plant. You can also supplement slow-release fertilizer with liquid fertilizer to encourage better blooms.
Proper fertilization can be complex and is not easily summarized in a brief overview; if you have any questions about how or when to apply fertilizer, the best detailed fertilizer information for our Florida landscapes is available from the University of Florida: https://edis.ifas.ufl.edu/entity/topic/fertilization
Careful and responsible use of fertilizer is critical to the health of our beautiful waterways, so please take advantage of the tremendous resources we have from the University of Florida and your local county Extension Office when you fertilize your landscape!
Cathy Dunn is a Lee County Master Gardener Volunteer and Garden Club of Cape Coral member.