Daniel Gill, Merrill, Thomas A.
In mid-April it’s time to do two things – pay taxes and fertilize your lawn. If you’ve already taken care of the taxes, now you should decide whether or not to fertilize your lawn.
In many situations, fertilizing your lawn is optional. If your lawn generally has been healthy and attractive over the years, you may choose to leave well enough alone.
That’s not to say applying fertilizer wouldn’t make a difference. I once convinced my dad to fertilize his front lawn by explaining that the grass would be darker green and grow better. A couple of months later he informed me that I had been right, but he swore he’d never let me fertilize his lawn again. The front yard was undeniably greener, but he had to mow it almost twice as often as the unfertilized backyard.
Lawns that definitely should be considered for fertilization are those that have sustained some damage in the past, which needs to be filled in by new growth. You also should consider fertilizing lawns that are thin or are poor in vigor and those where you desire a high degree of quality.
Since our lawns begin to green up in March, many gardeners wonder why we should wait until April to fertilize. Research shows that in March turfgrasses, such as St. Augustine, centipede and bermuda, undergo spring root decline. At that time much of the old root system dies and the grass grows new roots. So turfgrasses don’t have substantial root systems during March, even though the grass blades are beginning to grow.
If fertilizer is applied during that time, it can stimulate the grass to put its efforts into early leafy growth when needs to be growing roots. That means early fertilization can lead to the grass going into the summer season with a less developed root system.
Even more, if you fertilize when fewer active roots are present, the fertilizer will not be absorbed efficiently. In addition, what nutrients are absorbed from early fertilization can make lawns more susceptible to spring infections of brown patch, a disease especially common to St. Augustine.
As for what type of fertilizer you should use, let me first say there certainly are plenty of them out there, and it can be confusing. The best thing to remember is that there is not one best fertilizer. Just about any commercial lawn fertilizer would do a good job fertilizing your grass.
A fertilizer with an analysis that has about a 3:1:2 ratio would work fine. The ratio of a fertilizer’s analysis – the three numbers on a fertilizer package that tell you the percentages of nitrogen, phosphorus and potassium in that order – is found by dividing each number in the analysis by the smallest number of the analysis. A good general purpose fertilizer, such as 15-5-10, also is suitable for use on trees, shrubs and flowers, as well as your lawns, which simplifies your fertilizer purchases. Fertilizers with similar analysis such as 16-4-8, 12-4-8 or 19-5-9 also would be suitable.
Most fertilizers formulated specifically for lawns, such as 18-0-18 or high-nitrogen fertilizers such as 27-3-3, also will produce good results with turfgrass but would not be as suitable for general landscape use. Check the label of whatever fertilizer you buy, and make sure that one-third to one-half the nitrogen is slow release for extended feeding.
It’s a good idea to apply fertilizer to a lawn that has been mowed recently. That way the shorter blades allow the fertilizer granules to move down to the soil more efficiently.
The fertilizer should be evenly broadcast at the recommended rates found on the label. Read the label carefully, and make sure you apply only the amount of fertilizer recommended. This is very important, since over-application can damage or burn the grass.
It is best to use a fertilizer applicator to get even coverage. The drop-type applicator is recommended. Apply half the needed amount of fertilizer in one direction (east-west), then apply the other half in the other direction (north-south). Spreading the fertilizer granules by hand leads often leads to burned spots and uneven growth. Apply the fertilizer to dry turf, and water it in thoroughly afterward.
If you have a weed problem, you may use a "weed and feed" fertilizer that includes a herbicide to kill the weeds as you fertilize. Make sure you read the label directions carefully and follow them closely, since the herbicides in weed and feeds can be damaging to other plants in the landscape (such as trees and shrubs) if not used properly.
In addition, when using a weed and feed or similar product, make sure the herbicide in the product is safe to use on the type of lawn grass you have. Some herbicides that are safe to use on one type of grass may damage another. Finally, if you know the identity of the weed(s) you are having problems with, choose a product which lists that weed as one it will control.
Remember that fertilizing turfgrass is something we do to increase the quality of our lawns and is not a matter of life and death.
Gardeners who wish to push their lawns to be the most vigorous can fertilize again in June and make a final application in August. But one additional application in July will be adequate in most situations.
Centipede grass, a lower maintenance turf that requires less fertilizer that the other turfgrasses, generally is fine when fertilized just once in April.