Time To Fertilize – By Mark Govan, Host “Florida Gardening”

Winter’s grip has abandoned us to the warm days of spring. I can hardly believe what a mild winter we have had and as the first days of March are here, we need to start bringing our lawns and plants out of their winter dormancy. Some of us have probably noticed our lawns and plants have started to sprout new growth and I have even seen some of spring’s flowers starting to show their colors earlier than normal. This first glance of spring is a signal for us to give our plants the nutrients they need to continue this growth pattern. Remember, as our temperatures rise, turf grass and ornamental plants need additional nutrients to produce new growth needed to support flowers or increase the density of their root systems. Today we will go over the fertilization requirements of your lawns and ornamental plants. We will also discuss the proper amounts of nutrients you will need to apply based on the size of your lawn or the height of your plants.

            Selecting the correct fertilizer is just as important to your lawn as it is for your ornamentals. Turf fertilizers are meant to be used on turf and contain the nutrients turf grasses need to thrive. Ornamental fertilizers are geared to plants that flower and contain the nutrients necessary for their growth. Both types of fertilizers may contain differing amounts of Nitrogen (N), Phosphorous (P), or Potassium (K). Although each of these nutrients is necessary for proper plant growth, you will need to know the differences between them so you may provide your plants with the proper nutrition.

            Whether I am purchasing a turf or ornamental fertilizer, I prefer to purchase a balanced fertilizer that contains both primary plant nutrients and secondary plant nutrients. The primary nutrients (NPK) are responsible for plant growth, flowering, and root growth. Secondary plant nutrients such as calcium (C), sulphur (S), and magnesium (Mg), along with the minor essential elements such as copper, boron, molybdenum, zinc, and iron are just as necessary to proper plant growth. Knowing these elements are necessary for proper plant growth will help insure that you will read the label of the product you want to purchase to be sure these elements are included. Be careful not to buy a fertilizer based solely on price.

            Ornamental fertilizers need to have primary nutrients (NPK), secondary plant nutrients, and minor essential elements. Fertilizers containing additional phosphorus (P) are required for citrus, flowering trees, and shrubs. Remember, phosphorous helps plants flower and fruit trees need this element to produce quality fruit. Turf fertilizers do not need additional phosphorus as they do not need to flower or fruit. They do however respond to additional Sulphur, Iron, and Magnesium.

            Before I go over how much fertilizer to use on your lawn or plants you should know about the new slow release formulations now available. Slow release fertilizers are designed to release their elements to plants over a period of time. Liquid fertilizers or fertilizers mixed with water such as Peters or Miracle Grow release their nutrients very quickly. New labeling laws for fertilizer will state on the bag the amount of Slow Release Nitrogen (SRN) in the bag. The higher this number is the longer the fertilizer will last. SRN fertilizers last longer because they are either coated with a material that slows the release of nitrogen or they are derived from a nitrogen source which is slowly released over a period of time. SRN products are very important because if you put out a “quick release” nitrogen product, you have the possibility of “burning” your lawn or ornamentals. Look for fertilizers such as Florikan brands or Osmacote fertilizers which employ this type of SRN to protect your plants from burning. Because of the diversity of fertilizers and the nutrients they contain, you should read the label of the product you purchase before you apply.  

            In order to figure out how much fertilizer you will have to apply on your lawn, you will first need to know how big your lawn is. One of the easiest ways to figure this out is to know your lot size. Measure the length and the width of your lot and multiply these numbers by each other. If your lot is 100 feet long and 50 feet wide then you would multiply 100 x 50 = 5000 square feet. If the house on the lot is 1000 square feet then subtract this from the total lot size. (ex 5000 – 1000 = 4000 square feet). This is how much turf area you will need to purchase fertilizer for. Now you will need to figure out how much fertilizer to apply over a 4000 square feet lawn. The new fertilizer law passed last year forced fertilizer companies to list on the bag how much turf the bag would cover. Read the bag for this information or I can give you an example below.   

            If you purchased a 16-0-10 fertilizer for your yard, you will need 25 pounds of fertilizer to apply one pound of nitrogen to the entire lawn. If you purchased a 14-0-10 fertilizer for your yard, you will need to apply 28.5 pounds to give you the same result. As the first number (representing nitrogen) on the bag of fertilizer decreases, the more fertilizer you will have to apply. As this number increases, the less product you will need to apply. Most homeowners will need at least a 40 pound bag of fertilizer for their lawn to apply the right amount. Always apply fertilizer with a rotary type spreader and sweep spilled product off impervious surfaces. 

            Ornamental plants have a slightly different nutritional requirement than lawns have. Flowering plants need phosphorous, the middle number on a bag of fertilizer, to grow flowers or fruit. They also need the additional secondary plant nutrients and essential minor elements. Because our soil has few nutrients to help our plants we need to replenish them regularly.  Look for fertilizers with an analysis of at least an 8-10-10 or a 10-10-10. Read the bag to determine if any additional nutrients are included in the mix as noted above. Application of these fertilizers should also be made using a rotary spreader for even coverage. Trees and shrubs both require differing amounts of fertilizer to be applied.

            The amount of fertilizer applied to trees is based on the caliper or diameter of the trunk or stem. A good rule of thumb to follow is that for each one inch of diameter of trunk you should apply ½ pound of fertilizer. A good example would be if you have a tree that has a 6 inch diameter trunk, you will need to apply a minimum of 3 pounds of fertilizer around the tree beginning from a point halfway from the trunk of the tree to the end of the trees drip line and beyond. Fertilizer applied directly against the trunk of the tree is wasted as the trees feeder roots begin about halfway from the edge of the trees drip line and extend out from there.  

            Shrubs and flowering plants should be fertilized at a rate of 5 pounds per every 100 square feet of bed space. Do not apply fertilizer to your plants by hand as you will tend to throw fertilizer in a confined area. You should use a hand held fertilizer spreader available at any garden center. Hand held fertilizer spreaders hold about 5 pounds of fertilizer so just fill it up to the top and measure off a hundred square feet and go! Be sure to fertilize on both sides of your hedges as their roots go out in all directions and many people forget to put some fertilizer behind their plants. Plants with heavy nutritional requirements like roses, gardenias, or annuals need to be fed light applications more frequently. Do not be afraid to fertilize your plants frequently. Many plants like to be fertilized frequently in small doses.      

            I hope you enjoyed this section on fertilizing lawns and ornamentals. This is the time to get busy and get your lawns and gardens growing. I have already started! Thank you for your support and until next time, remember without plants we would not be here!

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