Fall Fertilizer


What to do this week –By Mark Govan, Host “Florida Gardening”

ABC Pest Control Inc. FloridaThis week I would like to touch on the importance of proper fertilization for our turf grasses, our ornamental plants, and our vegetable gardens. Even though winter is approaching, many of us have been unable to fertilize our plants during the summer due to fertilizer restrictions. Because of this, many of our plants are showing deficiencies in nitrogen, phosphorous, and potassium. Now is the time to correct these deficiencies.   Today, I would like to go over the proper selection of fertilizer based on the time of year, the specific nutrients you need to be aware of, and the application rates necessary to help our plants through the winter months.

Selecting the correct fertilizer is just as important for your lawn as it is for your ornamental plants and vegetable gardens. 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, including most vegetable gardens 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 all of these nutrients are necessary for proper plant growth, you will need to know the differences between them so you may provide your plants with the proper nutrition.

When I am purchasing a turf or ornamental/vegetable fertilizer, I prefer to purchase a balanced fertilizer that contains both primary plant nutrients and secondary plant nutrients. The primary nutrients such as nitrogen, phosphorous, and potassium (NPK) are responsible for plant growth (N), flowering or fruiting (P), and root growth (K). 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 although in smaller quantities for proper plant growth. Reading the fertilizer bag label will tell you which of these nutrients are included and which are not. Be careful not to buy a fertilizer based solely on price. Cheap fertilizers normally do not contain the secondary plant nutrients and are usually quick release which means they could possibly burn your plants.

Turf fertilizers recommended for fall treatments are different then springtime fertilizers. Fall fertilizer blends are usually lower in nitrogen but higher in potassium. Nitrogen is responsible for leaf or sheath growth we like to see in the spring but this type of growth is detrimental in the fall. Excessive leaf growth in the fall can be easily damaged by the cool or freezing temperatures. Higher levels of Potassium increase the root growth of the plant and the cold tolerance of the root system. Roots which grow deep in the fall allow the grass to respond quickly to warmer temperatures in the spring and give the turf a jump-start once spring arrives. Potassium also helps the grasses natural disease fighting capabilities.

Those of you whom are constantly bothered by lawn diseases such as brown patch fungus or grey leaf spot fungus should make it a point to apply more potassium in the fall to help decrease the spread of these diseases. An example of a turf fertilizer for fall lawn treatments would be a 14-0-10 versus a springtime fertilizer of a 16-0-8.  Turf fertilizers do not need additional phosphorus (the middle number) as we primarily look at turf for leaf growth and root growth. This is why turf fertilizers have a zero value in the middle of their analysis.

Ornamental fertilizers are formulated with the nutrients needed for the flowering or fruiting plants we use in our landscapes. These fertilizers normally have the standard primary nutrients (NPK), but in addition they contain secondary plant nutrients and minor essential elements needed. Fertilizers containing additional phosphorus (P) are required for flowering plants and fruiting trees. If you want to have more flowers or fruit you need a fertilizer high in phosphorous to increase your yield. Look for ornamental fertilizers which have an 8-10-10 on their label.

Fertilizers used in vegetable gardens should consist of a complete slow release fertilizer such as an 8-10-10 with micro-elements. These fertilizers should be incorporated into the planting mix prior to planting your vegetable garden. Some people will add fertilizer to their soil mix a few weeks before actually planting their vegetables to allow the soil to rest before planting. This procedure allows the fertilizer to begin to release their nutrients into the soil at the same time the vegetables are planted into the garden. 

Unlike turf and ornamentals, vegetables need a constant supply of nutrients to support their rapid growth. To ensure vegetables receive their proper nutrition, additional applications of a liquid fertilizer are necessary every two weeks. Liquid fertilizers such as Peters or Miracle Grow will feed the foliage through leaf absorption. I recommend at least bi-weekly applications of these products at one-half strength through the harvest. Liquid fertilizers deliver their nutrients directly into the plants leaves and stem to keep plants actively growing.

Before I go over how much fertilizer to use on your lawn or ornamental 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 this is why they need to be re-applied so frequently. New labeling laws for fertilizer will state on the bag the amount of Slow Release Nitrogen (SRN). 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. 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 one hundred feet long and fifty 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 have so you will need to purchase fertilizer to cover. In the past you may have had a hard time figuring out how much fertilizer to use but with the new fertilizer law passed last year, fertilizer companies now list on the bag how much turf the bag will 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 (100/16×4) to apply one pound of nitrogen to the entire 4000 sq ft 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. Always apply fertilizer with a rotary type spreader and sweep spilled product off impervious surfaces.

In order to figure out how much fertilizer your ornamental plants need you will have to figure out the square footage of the area to be treated. Measure the bed area the ornamental plants are in and then calculate. Example – If you have a hedge line that is five feet wide and thirty feet long (5 x 30), then this will give you one hundred and fifty square feet. For most average sized shrubs you need approximately five pounds of an 8-10-10 fertilizer per one hundred square feet of bed space. For the example above this means you will need about seven and one-half pounds of fertilizer to cover this area.

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.     Because our soil has few nutrients to help our plants, we need to replenish them regularly or every two months.

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 one-half 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.

Fertilizing may sound complicated to you now but you need to know the reasons behind proper fertilization requirements. Although I can never answer all questions you may have on what or how to fertilize, I hope this article will at least give you a starting place for proper plant nutrition. Thank you for your support and remember, without plants we wouldn’t be here!

2 thoughts on “Fall Fertilizer

  1. Samanthawms says:

    sounds like that would not be engouh water for such a young lawn, or at least that it isn’t long engouh. You will not get deep roots watering 15 minuets twice a day they will be very shallow and thus dry out easily. Also, fertilizing during the early growing period isn’t easy on the grass plants. I have a new lawn too and other than the initial fertilizer, I have held off on any more applications because it has been too dry and hot and I imagine it is hotter and dryer in NM. Absolutely you will not want to fertilize brown spots. The grass there *might* be dead already actually. Try this .water only every other day, but water more deeply, at LEAST 30 minutes per time, preferably more like an hour. After a week or two of this, start to cut back to watering every 3rd or 4th day, just as long though. The key is to water less frequently, but more deeply, to encourage good deep root growth. The brown areas though I would water every day, deeply, to see if you can get them to green up. If they don’t respond in a few weeks, you will likely have to cut them out and reseed.

    1. mgovan says:

      In my area of Florida we are bound by fertilizer restrictions which limit
      the times of year we can use fertilizers. Generally during the hot dry
      times
      we do not use nitrogen fertilizers. You do however have to water deeply.
      Watering deeply, at least an hour or one inch of water each time you water
      will be adequate but you must do this twice per week! Hope this Helps!

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