Fertilizer 411

Fertilizer 411

Fertilizer Spreader – Image Credit Les Harrison ,UF / IFAS Extension

Plants require nutrients to grow and they typically get them from the soil. Oftentimes, we apply fertilizer to help them along. Fertilizers provide specific nutrients for your plants and are available in a variety of different forms. When used correctly, fertilizers are a great tool that can help plants thrive. If used incorrectly, fertilizers can harm plants and also the environment.

Different plants have different nutrient requirements and in many cases, fertilizer may not be necessary so do your research before purchasing fertilizers. Sometimes, certain plants, like azaleas or blueberries, need a special formulation of fertilizer.

Think about having your soil tested to see what nutrients are already present in your soil. Contact your local Extension Office for sampling procedures.

Fertilizer Components

Most fertilizers used in the home landscape and garden are blends of several elements mixed together to create a specific formulation of plant nutrients.


Macronutrients are nutrients required by plants in relatively large amounts for optimum growth. The three main nutrients contained in fertilizers are nitrogen (N), phosphorus (P), and potassium (K). Most folks are familiar with these because they are represented by three numbers that appear on the fertilizer bag. You may be familiar with the term ‘complete fertilizer’. This means the fertilizer with contain all three of the major plant nutrients – N, P and K. Other macronutrients include calcium (Ca), magnesium (Mg), and sulfur (S).


Micronutrients are nutrients most plants need in small quantities. They are sometimes referred to as trace elements or minor elements. These nutrients include boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn). They are often available in sufficient quantities in the soil, but are also present in many fertilizers. Micronutrients are also sold as individual nutrients.

Types of Fertilizer

Inorganic Fertilizers

Inorganic fertilizers are materials that are mined or synthesized from non-living materials. Many inorganic fertilizers contain nutrients that are immediately available to plants. Others are formulated to be released over a period of time.

Organic Fertilizers

Organic fertilizers are materials that are derived from plants and animals. One of the most common forms of organic fertilizers is manure. Organic matter incorporated into the soil before planting will help fertilize your vegetable plants, but you’ll need to add additional fertilizer after planting.

The quick availability of nutrients, especially nitrogen, is very important in vegetable growing. Therefore, you may want to supplement any organic fertilizer you apply with some inorganic fertilizer for quick feeding. It is a common practice for gardeners to use a combination of fertilizers and techniques in the garden.

Slow- or Controlled-Release Fertilizers

Slow- and Controlled-Release fertilizers provide nutrients to plant roots over an extended period of time. This allows you to fertilize less frequently and prevent nutrients from leaving your landscape and entering groundwater or waterways.

Understanding a Fertilizer Label

The fertilizer label includes a series of numbers that indicate the percentage of nitrogen, phosphorous, and potassium, by weight. The numbers will read something like 15-0-15 or 16-2-8. The first number represents the percentage of nitrogen in the bag, the second refers to phosphorus, and the third number is the amount of potassium. For example, a 50-pound bag of 16-2-8 is 16% nitrogen (8 pounds total); 2% phosphorus (1 pound total); and 8% potassium (4 pounds total). The remaining weight is usually comprised of inert ingredients.

Preventing Pollution

  • Follow UF/IFAS Recommendations. Rates, application timings and formulas vary depending on the plant.
  • Do not fertilize before a heavy rain. If rain is in the forecast for the next 24 hours, wait to apply fertilizer. Heavy rains can cause fertilizer to leach into groundwater.
  • Keep fertilizer off hard surfaces. If fertilizer is spilled on a driveway or sidewalk, sweep it up and dispose of it. Fertilizers can wash into storm drains and nearby bodies of water.

For more information on fertilizers visit:

The Fertilizer Label

Resurrection Ferns Making Their Appearance

Resurrection Ferns Making Their Appearance

Resurrection Fern on Pecan Tree. Image Credit Danielle Sprague, UF/ IFAS Extension

This week, I received a call about identifying a plant growing on a pecan tree in someone’s yard. With the recent rain we’ve experienced after a rather dry period, I had a pretty good feeling it was a resurrection fern. A quick picture sent in to me by the homeowner confirmed this.

Resurrection fern, Pleopeltis polypodioides is a native fern found in many hardwood trees throughout the southeast. In our area, it is found most often on the branches and trunks of live oak and pecan trees. The resurrection fern gets its name from its ability to withstand extensive periods of drought by shriveling up and appearing dead. When it is exposed to water again, it will ‘come back to life’, uncurling its fronds and appearing bright green.


This creeping fern has a long, skinny stem to which the fronds or leaves are attached. The stem is less than 1/12″ in diameter and fronds are anywhere from 4 to 12 inches long. Unlike other plants, resurrection fern reproduces by spores, not seeds. These spores can be found on the underside of the fronds in clusters known as sori. The sori look like brown to black scales.

Resurrection Fern before and after, Image courtesy IFAS Gardening Solutions

Resurrection fern is a perennial epiphyte or ‘air plant’, meaning that it attaches itself to other plants, but it does not steal water or nutrients from its host plant. Instead, it absorbs water and nutrients that collect on the outer surface of the bark. One of the questions posed by the homeowner was the need to control the resurrection fern, however, since it is an air plant and does not harm the tree, there are no chemicals recommended to control it.

In 1997, the resurrection fern made its first debut in outer space! Because of its unique attributes, the National Aeronautics and Space Administration (NASA) launched into space for an experiment to study the ‘resurrection’ in zero gravity. Amazingly enough, they found that the resurrection fern was able to rehydrate and recover in zero gravity!



For more information on resurrection ferns:

UF/IFAS Gardening Solutions: Resurrection Ferns

Island Ecology: Resurrection Ferns

Beware of Root-Knot Nematodes in Your Garden

Beware of Root-Knot Nematodes in Your Garden

Recently, I received a call about a garden not producing the way it used to. After speaking with the homeowner, I decided to take a visit to see what was going on. On my visit, I could see that the tomatoes were stunted, yellow and wilting, the squash plants were flowering but not setting fruit, and the okra was stunted. After digging up some of the sick plants and examining the roots, the problem was as clear as day…root-knot nematodes.

Galls on roots from root-knot nematodes

Root-knot nematodes are microscopic, unsegmented roundworms that live in the soil and feed on the roots of many common garden plants. Some of the most commonly damaged crops are tomatoes, potatoes, okra, beans, peppers, eggplants, peas, cucumbers, carrots, field peas, squash, and melons. Root-knot nematodes enter the root and feed, causing knots or galls to form. These galls are easily recognizable on the roots. If you’re inspecting the roots of beans or peas, be careful not to confuse nematode galls with the nitrogen-fixing nodules that are a normal part of the root system. As the nematodes feed, the root system of the plant becomes damaged and the plant is unable to take up water and nutrients from the soil. As a result, the plant may show symptoms of stunting, yellowing, and wilting.

What can I do about nematodes?
There are currently no nematicides labeled for use in the home garden but the best means of root-knot nematode management involves using a combination of strategies that make your garden less susceptible to attack.

Grow Resistant Varieties
Some varieties of crops are resistant to root-knot nematodes. This means is that a particular nematode can’t reproduce on the plant roots. When buying seed, read the variety label. The label may have ‘VFN’ written in capital letters. These letters indicate that the variety has resistance to certain diseases: V = Verticillium wilt; F = Fusarium wilt; and N = root-knot nematode. It’s best to use resistant varieties when root-knot nematodes are present.

Tomato plant showing signs of nematode damage – yellowing and wilting.

If you suspect you may have a nematode problem, be sure not to move soil or infected plant roots from an infected area to a clean area. Nematodes can easily be spread by garden tillers, hand tools, etc. so be sure to disinfect all equipment after use in problem areas.
Infected roots left in the soil can continue to harbor nematodes. After the crop is harvested, pull up the roots and get rid of them. Tilling the soil can kill nematodes by exposing them to sunlight.

Cover crops and Crop Rotation
Cover crops and crop rotation isn’t just a concept for farmers…gardeners need to implement the same practices! While this may take some planning, it is the most effective way to reduce pests and diseases.
Cover crops are crops that are not harvested and are typically planted between harvestable crops. They help improve soil quality, prevent soil erosion, and help control pests and diseases. Selecting cover crops that aren’t susceptible to root-knot nematode attack is key. When growing a cover crop that nematodes can’t reproduce on, populations should decline or not build up to begin with. Grain sorghum and millet can be planted as a summer cover crop and rye in the winter. French marigolds have been shown to reduce nematode populations as well.
Another simple way to manage root-knot nematodes is by crop rotation. Crop rotation is the practice of not growing crops that are susceptible to nematode attack, in the same spot for more than one year. Crops that aren’t susceptible to attack are cool season crops in the cabbage family such as broccoli, cauliflower, Brussels sprouts, collards and kale.

Root-knot nematodes can wreck havoc on a garden so it’s important to take the necessary precautions to avoid them. It may require planning and patience but it will be worth it in the long run!

For more information on this topic, use the links to the following publications:

Nematode Management in the Vegetable Garden

Featured Creature: Nematodes

Citrus Leafminer in Dooryard Citrus

Citrus Leafminer in Dooryard Citrus

Citrus leafminer injury. Photo: James Castner

Spring is in full swing and citrus trees have begun actively flushing. With the new flush comes an array of insect pests. One of the most common being the citrus leafminer. The citrus leafminer is a small white moth, about 2.4 mm in length. It is more easily detected during its larval stage by the serpentine larval mines it produces on the underside of citrus leaves.

Citrus leafminer adult. Photo: James Castner

The larvae of the citrus leafminer feed on the new growth or flush of citrus causing serpentine mines to form under the leaf cuticle. This can result in leaf curling and distortion. Citrus leafminer injury to foliage can stunt the growth of young trees and in areas where the citrus canker pathogen is present, provide an opening for infection.

Distortion and leaf curling caused by citrus leafminer. Photo: Danielle Sprague

The term ‘flush’ is commonly used to describe the new foliar growth between bud break and shoot expansion. Citrus trees usually have several flushes per year, depending upon cultivar, climate and crop load. Generally, most citrus cultivars in our area have around three flushes. The main flush is the spring flush in late winter/early spring. Following that, two additional flushes occur around the end of June and late September.

Citrus leafminer on young flush. Photo: Danielle Sprague

Adult leafminers require the new citrus flush for development. Eggs are laid within the flush. After two to ten days, the larvae emerge and feed causing the mines to occur. Larvae are protected within the leaf and therefore difficult to control. Pupation occurs within the leaf mine and takes anywhere from six to 22 days, depending upon temperature. Adults emerge around dawn and are most active in the morning and evening. In Florida, one generation of citrus leafminer is produced about every three weeks but populations increase when citrus trees are flushing.
In Florida, several natural enemies assist with reducing citrus leafminer populations. Studies have shown that predation from natural enemies can reduce leafminer populations by 90%. Primary predators of citrus leafminers include ants, lacewings and spiders. A parasitic wasp, Ageniaspis citricola was introduced into Florida and has become established. The parasitic wasp attacks the immature stages of citrus leafminer. Ageniaspis citricola can be requested and obtained for free from the Florida Department of Agriculture and Consumer Services (FDACS). Because it is a specialized parasitoid of the citrus leafminer larval stage, it should be released only when mines start to become visible on flush.
Citrus leafminer can be difficult to control with insecticides due to the fact that they are within the leaf and protected. Applications of insecticides require proper timing and may require repeat applications. For a full list of insecticides, contact your local Extension Office.

For more information on citrus leafminer, use the links to the following publications:

Citrus Leafminer, Phyllocnistis citrella Stainton (Insecta: Lepidoptera: Phyllocnistinae)

Citrus Leafminer Control – UGA

Planning the Garden: Crop Rotation

Planning the Garden: Crop Rotation

With spring on the horizon, many of us are planning or have already began to plant our spring gardens. If you’re still in the planning process like me, one very important thing to consider is the importance of crop rotation in the garden. Crop rotation is a concept that’s been used by farmers for many years but it’s a concept that gardeners need to adopt as well!

What is crop rotation?

Crop rotation is a method used to reduce insect pests, disease and manage soil fertility by changing the planting location of vegetables within the garden each season. Each vegetable is grouped into a plant family. Vegetables in the same plant family typically are able to harbor the same kinds of insect pests and diseases, and have the similar nutrient requirements. When vegetables belonging to the same plant family are planted in the same location over and over again, pest populations can build up and productivity of the garden decreases. In addition, fertility issues can arise from planting the same crops, in the same area over again. Since different crops require different types and amounts of nutrients, crop rotation can help even out the loss of soil nutrients.

List of common vegetable families.

How should I plan for crop rotation in my garden?

First, consider the vegetables you would like to grow this season then group them by their families. Vegetable crops in the same family should NOT be planted in the same area year after year. For example, if squash is planted in a bed or one area of the garden one year, cucumbers or watermelons should not be planted in the same area of the garden the following year because these plants belong to the same family (Cucurbitaceae).

Divide your garden according to the number of plant families you want to grow. This could be in rows or even separate beds. From there, you will want to think about your ordering sequence. For example, if you are planting a legume (beans or peas) that fixes nitrogen back into the soil this spring, you’ll want to plant a heavy feeding crop like broccoli this fall. Heavy feeding crops can be followed by light feeding crops such as carrots or onions. Be sure to keep a gardening journal as a reminder of what is planted each year and season.

Crop rotation is one of the most effective methods we have to manage the many pests and diseases we have here in Florida. If you’re struggling with a particular pest or disease in your garden, consider using crop rotation to help manage it. For more information on crop rotations for the home garden, contact your local extension agent.