Daniel Gill, Merrill, Thomas A. | 4/5/2006 12:01:32 AM
By Dan Gill
LSU AgCenter Horticulturist
Fertilizing lawns is best done in early to mid-April. Some people try to rush it and fertilize earlier, but it’s important to wait until the right time – which is about now.
By this time, our warm-season lawn grasses, such as centipede, St. Augustine, bermuda and zoysia, have begun active growth, re-established a strong root system and are now ready for the extra nutrients fertilization provides.
In many situations, fertilizing your lawn is optional. If your lawn generally has been healthy and attractive over the years with only occasional fertilization, you may choose to leave well enough alone this year. It’s not that fertilization wouldn’t make a difference. For example, I once convinced my dad to fertilize his front lawn – 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 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 and need to growth to fill in damaged spots, those that are thin or are poor in vigor and those whose owners 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. That means 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 it needs to be growing roots. Put another way, early fertilization can lead to the grass going into the summer season with a less-developed root system. Even more, with fewer active roots present, the fertilizer will not be efficiently absorbed. 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 when the time is right, there certainly are plenty of them out there – and it can be confusing. Just remember there is not one best fertilizer. Just about any commercial lawn fertilizer would do a good job fertilizing your grass. But be sure to check the label of whatever fertilizer you buy and make sure that one-third to one-half the nitrogen is designed to slowly release for extended feeding.
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.
Fertilizers with a 3:1:2 ratio, such as 15-5-10, also are suitable for use on trees, shrubs and flowers, as well as your lawn, which simplifies your fertilizer purchases. Fertilizers with similar analyses, 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, will produce good results with turfgrass but are not as suitable for general landscape use.
It’s a good idea to apply fertilizer to a lawn that has been mowed recently. The shorter blades will allow the fertilizer granules to move down to the soil more efficiently. The fertilizer should be evenly broadcast at the rates recommended on its label. Read the label carefully and make sure you apply only the amount of fertilizer recommended. This is important, since over-application can damage or burn the grass.
It is best to use a fertilizer applicator or spreader 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 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" type of 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. Also 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. For gardeners who wish to push their lawns to be the most vigorous, you can fertilize again in June and make a final application in August. On the other hand, one additional application in July will be adequate in most situations. Centipede grass, a lower-maintenance turf that requires less fertilizer than the other turfgrasses, generally is fine if it is just fertilized once in April.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.