Fertilization is a subject that throws many a gardener for a loop. It can be confusing, and we in the professional horticulture world understand. This topic will almost always be approached from the prospective of nitrogen. So why does nitrogen get so much attention? What is its role in plant growth? Nitrogen is the primary driver of protein synthesis, plant metabolism, energy creation, and is the structural component in chlorophyll. These are all extremely important functions leaving little doubt as to why it’s so critical. Your plants use this resource abundantly for healthy growth. The reason it gets so much attention is owing to its frangibility in the soil. Nitrogen goes through changes once applied to soils and is readily lost to the environment. For this reason, nitrogen application needs to be timed appropriately, and your cultural practices need to be such that encourage plant uptake over losses to the environment. Fear not my friends, this article will bolster your insight into the wonderful world of nitrogen, and have your plants growing strong and healthy.
The What and Why of Nitrogen
Nitrogen is one of three macronutrients identified in every fertilizer bag as the first of three numbers. This standardized NPK labeling refers to the amount of this nutrient in the bag by percentage of total weight. Application rates should be based on this number, and how much nitrogen you’ll need to cover a specified area. which number you use is based on the equipment you have to apply more so than the plant requirements.
UF/IFAS Photo: Dan Culbert
Nitrogen can be natural or man made. Natural sources come in the form of composts, manures, and through atmospheric deposition. The later of these sources means rain, which washes nitrogen out of the atmosphere and into your soils. Man made sources conversely come in bags and are the result of a combustion process developed by Fritz Haber, and Carl Bosch circa 1910. Either way, nitrogen will be in the form of ammonia, nitrate, ammonium, or urea. Knowing this is important as it will dictate application methodologies. For instance, urea applied to the surface will escape into the atmosphere if not incorporated into your garden.
UF/IFAS photo: T.W. Shaddox
Nitrogen type will also affect soil pH. This is especially important with ammonia-based fertilizers as residual acidity from them may lower pH. Applying the correct type will mitigate large unwanted changes in soil. Why are we concerned with soil pH? It speaks to nutrient availability and, thus how well your plants grow. It can be overwhelming, but with soil testing and a call to your extension office, it’s easy to identify the appropriate fertilizers for your application.
Reactions in Soils
Soil is often considered inert, holding plants in place while providing a pantry full of the nutrients they crave. Nothing is further from the truth. Soil is a living entity with its own physical and chemical properties. The addition of anything, including irrigation, affects these properties.
Nitrogen takes two forms in your soil aside from nitrogen source. Inorganic nitrogen is converted from soil organic matter in a process known as mineralization or added from bagged fertilizers and is available for plant uptake. Organic nitrogen is unavailable for plant uptake and will be present in the natural forms listed in the previous section. Both are susceptible to the nitrogen cycle and may be lost to the environment. This happens as water passes through soil (leaching), erosion, runoff, or is lost to the atmosphere through volatilization and may have negative effects on surrounding water bodies.
UF/IFAS Photo
To mitigate these risks through responsible fertilizer application, irrigation management, and landscape design. Apply fertilizers when plant uptake is favorable, and only to the level required by your plants. This will be during heavy vegetative growth periods such as initial installation. Irrigate as dictated by your plant life vs on a timer. Watering is a vital practice, but often overdone. Keep water levels enough to avoid plant stress but not excessive. Doing so reduces leaching potential and will keep your plants healthier. Finally, design your landscape with Florida Friendly Landscaping principles. Integrate diverse plant life, including turfgrasses and landscaped beds. The goal here is to allow enough plant life to absorb excess storm water, and support local pollinator populations.
Nitrogen is a critical piece of your fertilizer routine. It’s important to understand how it reacts with both your plants and your soils. A little knowledge can go a long way to keeping your plants healthy while mitigating risks from over fertilization. For more information, see this Ask IFAS document, or contact your local extension agent for additional information on this and any topic regarding your gardens and more.
We are nearing the end of the NO MOW MARCH launch that several counties participated in this month. Maybe you have been mowing this month because you live in an area where it is required or maybe you were able to go the whole month but now you are wondering what’s next. The fact is that keeping a lawn healthy can maximize plant use and minimize environmental adverse impacts. In this article we will talk about the steps to help keep a healthy lawn.
Mowing is one of the most important aspects of maintaining a good quality lawn. When using proper mowing practices along with fertilization and irrigation, you can increase the density of your turfgrass. This produces a tighter lawn that the weeds cannot compete with and naturally reduces those unwanted weeds. Cutting height and frequency are the most important factors to consider when mowing. This will vary by turfgrass species, cultivar, and maintenance level of lawn desired. If too much leaf tissue is removed at one mowing cycle it can cause your turfgrass to stress. Over time the damage could be insects, disease, drought and sunscald. Leaf clippings are beneficial to the turf and give back nutrients and organic matter to the lawn. Some other helpful tips are to keep your mower blades sharp, do not mow grass when wet (I know this can be very difficult when we get into the rainy season.), and if you have several properties that you are mowing it is good to remove clippings and weed seeds from the mower. These tips can help improve the appearance and greatly reduce insect and disease infestation. For more details on your specific type of lawn refer to this document: ENH10/LH028: Mowing Your Florida Lawn (ufl.edu)
Turf can benefit from fertilization but only if done correctly. Timing and the appropriate rate can help maintain a healthy Florida-Friendly lawn. The turf roots and shoots need to be actively growing and this can vary depending on the use of the area, water stress (presence of rain or irrigation) and the environment of where the grass is grown. For North and Central Florida active growth occurs from spring through fall. Our neighbors down in South Florida can see growth year-round. Fertilizing when your grass is dormant not only wastes time and money, but it may also contribute to nutrient leaching or runoff. This is the perfect time of year to do a soil test to see exactly what nutrients are available and what your soil is lacking. This article will give you more insight on soil testing for Florida turfgrasses SL 181/SS317: Soil Testing and Interpretation for Florida Turfgrasses (ufl.edu)
Turf Fertilizers; Photo taken by: Ashley Stonecipher
There are many benefits to having healthy turfgrass. It can slow stormwater from moving to water bodies. Healthy turf can filter and remove contaminants and help protect our ground water. Leaching and erosion are also reduced when you have healthy dense turfgrass. In Florida there are environmental stresses that may alter the required management level and health of the turf. Using proper cultural practices can alleviate the effects of stress. For instance, during times of drought do not try to fertilize until water is available, increase mowing heights in shaded areas to avoid thinning, and avoid effects of vehicle and foot traffic on stressed turf. ENH979/EP236: Homeowner Best Management Practices for the Home Lawn (ufl.edu)
Just by hitting on some of these key aspects such as the mowing height, cultural practices and the timing and rate of your fertilizer can make a difference in the health of your turf. Remember a healthy dense turf means less weeds and less insect and disease pressure later in the season. For more information or questions concerning your lawn please contact your local extension office!
Variegated shell ginger is a good choice for adding color to shaded areas of the landscape. Photo by David W. Marshall.
What to Do in the Garden in March and April
Written by David W. Marshall, UF/IFAS Leon County Extension Agent Emeritus
Except for a couple of freezes, it has been a relatively mild winter. But those freezes were cold enough and long enough to kill many tropical plants almost to the ground. Will we have more freezes? It’s possible, though after we reach mid-March, the probability drops significantly.
Some plants, such as this firebush, had stems killed back to the ground by the cold and will re-sprout from the root system. Photo by David W. Marshall.
So, when can you start cleaning up all the cold damaged plants? You probably have the urge to do it as soon as possible, as the brown foliage and stems are a little depressing. Many of us have lots of cold-damaged plants and we want to get the cleanup finished. First, though, examine the plants to determine the extent of the cold damage. Scrape the bark with your fingernail or use a pocketknife to see if the tissue beneath is still green or if it has turned brown due to cold damage. In many cases, you will find that the stems have been killed back to within a foot of the ground. On other plants, you may find that some of the stems still appear green higher up and you may not have to cut them back quite as far. If that’s the case, you may wish to wait until mid-March to cut these plants back. In case we have another hard freeze, the damaged growth may offer a little insulation to the undamaged parts of the plant. With most plants there’s no real need to cut them back until the new growth starts popping out, probably in late March.
The stems of butterfly gingers can be completely removed now. Many of these will just pop off when pulled lightly. Others may have to be cut, but it won’t hurt them. Variegated shell gingers, in many cases, will still have some undamaged growth mixed in below the brown leaves. You won’t kill a well-established shell ginger by cutting it back now, but because of the insulating effect of the brown leaves, it’s probably best to wait until mid-March to cut them back.
Azaleas and camellias, typical of a North Florida spring, were blooming by late February this year. If you don’t have some of these in your yard, now is a good time to plant. Photo by David W. Marshall.
You may have other shrubs that you wish to prune now also. Wait to prune spring bloomers like loropetalum and azalea until after they finish flowering. Some overgrown shrubs may need to be cut back hard to rejuvenate them, and if you do it now, they will have longer to recover. Before crepe myrtles start putting out new leaves, work on the shape of the tree. Remove poorly placed rubbing and crossover branches by cutting all the way back to the trunk or branch from where they grow. Don’t, however, top the tree unless you are purposely trying to pollard the tree and completely understand how to do it correctly. Otherwise, you will likely end up with a mess.
In mid-March, be prepared to plant warm-season vegetables such as tomatoes, snap beans, pole beans, lima beans, sweet corn, southern peas, squash, and watermelons. So, make sure you have the garden tilled before then. If you wait until April or May to plant, your harvest will be later and the insect and diseases will get much of the crop. Warm-season herbs can be added after mid-March.
Don’t be overly anxious to fertilize your lawn, especially if you have centipede grass. Wait until at least mid-March. Make sure the lawn has been fully green for three weeks before fertilizing. If this pushes you into April, fine. It’s better to fertilize too late than too early. Centipede lawns that are fertilized too early often have spring yellowing problems. St. Augustine grass is more forgiving, but don’t fertilize it either until at least mid-March. Use 6.7 pounds of 15-0-15 fertilizer per 1,000 square feet of lawn area. If the fertilizer doesn’t contain at least a third of its nitrogen in a slow-release form, though, cut the application rate in half.
Most of the weeds in the lawn now are winter annuals that will die out as the weather gets hotter. Just keep your lawn mowed regularly until they do. If you usually still have problems with weeds in the summer, though, you could use a pre-emergent herbicide to reduce the emergence of the summer weeds.
To keep fire ants out of your yard, broadcast a bait formulated product over the entire yard, according to the label directions. Plan to treat again in fall. You can quickly apply the bait using a small hand spreader available from your garden center.
Now, before it gets hotter, add some colorful camellias to your landscape. Photo by David W. Marshall.
Now, before it gets hotter, add some colorful azaleas, camellias, roses, and loropetalum shrubs to your landscape. Also consider fragrant plants such as tea olives, banana shrubs, and sweet viburnum. The sooner you plant these in the spring, the quicker they will get established and grow.
Lavender trumpet vine (Clytostoma callistegioides), crossvine (Bignonia capreolata), coral honeysuckle, and Confederate jasmine are vines that flower during this period of the year. Now is a good time to plant them also.
Don’t forget groundcovers such as liriope, Lomandra, Mondo grass, Dianella (New Zealand flax), African iris, or any of a variety of ferns. Groundcovers planted now will have a full growing season to get established. Groundcovers are often a good choice for plantings in front of the house where you don’t want tall shrubs.
Add some long-blooming seasonal color to your yard this spring. Once we reach mid-March the nurseries will be loaded with many possibilities. Petunias will give you a lot of color in sunny areas for about three months. After the summer rains start in June they normally decline. Pentas will hold up on through the summer and into fall. They prefer full sun but will take a little filtered sunlight too. Sunpatiens® will work in sun or shade and should hold up through the summer. Melampodium will give continuous yellow blooms in sunny areas through summer and into fall. Torenias, especially the trailing or vining types, are excellent for providing low-growing color in areas that receive morning sun but not so much harsh afternoon sun. But there are many other options, too, so visit a full-service nursery with knowledgeable employees that can guide you.
Pentas can be planted in mid to late March and will give color until late fall. Plant in full sun to light shade. Photo by David W. Marshall.
Also, later in the month, start planting perennials such as firebush, angel’s trumpet, cigar flower, and Turk’s cap so you will have color later in the season that will last into fall. These perennials will return each year, even if the tops get frozen back.
There’s no need to fertilize mature trees and shrubs that are growing well. But young plants which you’re trying to encourage to grow will benefit from an application of fertilizer now. The same 15-0-15 that you used for the lawn can be used on trees and shrubs, provided it’s not a weed-and-feed product with an herbicide. The exception would be with palms, especially if you’ve noticed that your palms haven’t been looking that healthy. Use an 8-2-12 or similar palm fertilizer that has four percent magnesium and micronutrients also. If you have a lot of palms in the lawn, just use this palm fertilizer on your whole lawn.
If you didn’t get around to fertilizing fruit plants in February, do it now. After mid-March is also a good time to plant new citrus trees such as satsuma, orange, or grapefruit. You have a full growing season ahead!
Anything that you plant now will need regular watering. That’s what they were receiving in the nursery. Remember that for several months, at least, all the roots will still be in the root ball that was in the pot, even after you put the plant in the ground. So, soak this root ball at least every other day. Don’t rely on a sprinkler system that only comes on once or twice a week. That’s not enough water for the limited root systems of new plants.
Written by David W. Marshall, an Extension Agent Emeritus with UF/IFAS Extension Leon County.
Our Gardening in the Panhandle blogs cover many horticultural topics concerning yards, however let us not forget about properties that contain a body of water (pond, lake, retention or detention basin, stream, river or Gulf of Mexico). Out of the nine Florida-Friendly Landscaping™ principles, five directly deal with water quality. Those principles are #2 Water Efficiently, #3 Fertilize Appropriately, #6 Manage Yard Pests Responsibly, #8 Prevent Stormwater Runoff, and #9 Protect the Waterfront. An easy argument can be made that the remaining four principles (#1 Right Plant, Right Place, #4 Mulch, #5 Attract Wildlife, and #7 Recycle) can also impact water quality on your properties.
Photo Credit: University of Florida/IFAS Extension
The quickest and easiest way to start improving water quality is setting up a maintenance-free zone along your shore. At minimum, you should keep all chemicals 10′ away from the water’s edge and increase that distance as your slope becomes steeper. Chemicals include all fertilizers (#3) and any pesticides/herbicides (#6) meant for the landscape (there are times when situations arise where treatment of the water is warranted). If you must fertilize up slope, make sure to reduce irrigation (#2) to about 25% of normal the first time which keeps the fertilizer from dissolving and running down your slope’s surface (#9).
Cascades Park in Tallahassee, FL.
If possible replace turfgrass with a no mow zone containing plants adapted for shorelines to prevent applications of fertilizer and chemicals. Plants (#1) other than turfgrass will have deeper roots, stabilize the bank better and absorb more chemicals before entering the water. These taller plants in turn can become habitats (#5) for birds and other specimens which can increase your ecosystem’s biodiversity. Some properties have collection swales or low lying areas where water pools and then flows into the water. It is best to understand how water flows through the property and reduce chemicals in those areas too (#8).
Heavy rains caused water levels to raise around this pond and decomposing leaf litter added a film over the pond.
As gardeners, we tend to compost our leaves and yard debris (#7) plus use mulch (#4) to reduce water loss from our soils. Keep mulches and compost piles away from flood zones and when possible keep leaves from washing into your water as they can create films on the surface. Never allow grass clippings to land on water surfaces as they will add nutrients when tissue decays.
As Florida continues to grow, we all must play an important role in keeping our water clean and safe for us, animals, birds, and aquatic life. If you have questions on improving your water quality, please contact your local county Extension Agent or Water Regional Specialized Agent (RSA). For additional information visit these other sites.
Urban Fertilizer Ordinances in the Context of Environmental Horticulture and Water Quality Extension Programs: Frequently Asked Questions: https://edis.ifas.ufl.edu/publication/AE534
Our trees and vines are flowering and lawns are starting to green up naturally, but one glance at the calendar and it is still early spring. The last official frost date for the Florida panhandle can be into April depending on location. We know our day time and night time temperatures are still fluctuating every other day. We also know the stores and nurseries are stocked with shelves and pallets of fertilizer. So the big question is when can I fertilizer my lawn?
Overseeded ryegrass on a centipedegrass lawn.
My answer after years of practice is always it depends, but my non-scientific rule of thumb to homeowners is wait until you mow three weeks in a row and make sure you’re past the last frost dates for your area. If you need to mow three weeks in a row for height, then your lawn is actively growing and most likely we are into a temperature range good for fertilizer applications. If you apply fertilizer to a lawn that is dormant, the fertilizer will not be taken up by your roots and it can leach below the root zone wasting money while not improving the lawn and possibly causing environmental concerns.
With that said, there are some factors to consider. We always recommend doing a soil test first. This can be done in advance of spring. Your test results might indicate having sufficient nutrients in the soil, so not applying would save you money and the lawn would still look good. The soil test will also indicate what nutrients are in excess or lacking, then you can apply only the nutrients needed.
I have found that fertilizer is still very much misunderstood. When I ask homeowners whether they consider fertilizer to be medicine or a stressor, most will answer medicine and we all know if a little medicine is good, then a bit more is better. However, it is more accurate to think of fertilizer as a chemical stressor. If my lawn is unhealthy, then I force my lawn to grow and it can further weaken my plants. Think of it like this, if you’re not feeling well at night before you go to bed, should you consume one of those big energy drinks? Not if you want to sleep and hopefully feel better in the morning. Apply fertilizer when the lawn is ready and capable of having a positive response when spring fully arrives.
Wakulla County Extension office mixed species turf.
Here are some items you should know before you fertilize the lawn. Fertilizers used in Florida should have a license number that begins with F followed by a series of numbers. It is important to check your fertilizers before you apply. You need to know what type of turfgrass you have in your lawn. We have a lot of bahiagrass and centipedegrass lawns in the panhandle. Each will require a different regiment. You are only allowed to apply one pound of nitrogen per 1,000 square feet per application and you should never apply more than the recommended rate. I always refer to a childhood fable “The Tortoise and the Hare” when thinking about plant health. Slow and steady makes for a better lawn in the long run. This means you need to measure your lawn, understand how to calculate the nitrogen and then apply correctly with the right equipment and spreader patterns. We also recommend very little phosphorus (the middle number on the fertilizer bag 15-0-15) for Florida lawns. Our soils are usually sufficient and this is another item your soil test results will confirm.
Remember, your local Extension office is always here to help especially making sure you treat the lawn right. Think before you apply because your long-term goal is improving the lawn quality.
The Florida Fertilizer Label (https://edis.ifas.ufl.edu/ss170) and General Recommendations for Fertilization of Turfgrasses on Florida Soils (https://edis.ifas.ufl.edu/lh014). T. W. Shaddox, assistant professor; UF/IFAS Fort Lauderdale Research and Education Center, Ft. Lauderdale, FL 33314
Homeowner Best Management Practices for the Home Lawn (https://edis.ifas.ufl.edu/ep236). Laurie E. Trenholm, professor, Extension turfgrass specialist, Environmental Horticulture Department; UF/IFAS Extension, Gainesville, FL 32611.
Bahiagrass for Florida Lawns (https://edis.ifas.ufl.edu/lh006). L. E. Trenholm, professor, turfgrass specialist, Department of Environmental Horticulture; J. B. Unruh, professor, turfgrass specialist, UF/IFAS West Florida Research and Education Center; and J. L. Cisar, retired professor, turfgrass specialist, UF/IFAS Ft. Lauderdale REC; UF/IFAS Extension, Gainesville, FL 32611.
Centipedegrass for Florida Lawns (https://edis.ifas.ufl.edu/lh009). J. B. Unruh, professor, turfgrass specialist, UF/IFAS West Florida Research and Education Center; L. E. Trenholm, associate professor, turfgrass specialist, Environmental Horticulture Department; and J. L. Cisar, professor, turfgrass specialist, UF/IFAS Ft. Lauderdale REC; UF/IFAS Extension, Gainesville, FL 32611.
