Mid April best time to fertilize North Florida lawns

It’s too early to fertilize our warm-season lawn grasses now. This includes the use of fertilizers contained in weed-and-feed products.

There are a number of reasons why it’s best to wait to fertilize your lawn.

First, the soil temperature is too cool for grass roots to have access to some of the fertilizer elements. For example, iron and potassium are poorly available until the soil warms up in spring. Some nutrients leach below the grass roots because the lawn can’t use them yet. This results in waste of fertilizer, time and money.

Secondly, fertilizing too soon can induce nutrient deficiencies and off color areas in your lawn. This is one cause for bright yellow areas in lawns during early spring. Nitrogen is readily taken up by the lawn, even under cool soil conditions, and stimulates early green growth. But the early lawn growth is dependent on iron also being readily available. But iron is poorly available under the cool soil conditions of late winter and early spring. So the lawn turns yellow in areas due to an iron deficiency caused by an early fertilizer application. Many times, as soil temperatures warm during mid April and May, the iron becomes available and the lawn turns green. So why not avoid this scenario by waiting until mid April or May to fertilize your lawn?

It takes consistently warm night temperatures to allow the soil to become warm enough for best root growth and optimal uptake of fertilizer.

Thirdly, the young, tender grass roots that are beginning to grow in early spring are easily burned by the fertilizer.

Fourthly, fertilizing too early can stimulate early lawn growth, which is tender and easily injured by a late frost. The average date for our last killing frost is mid March.

Also, be very cautious about using weed-and-feed products that recommend a late winter application. These products are usually high in nitrogen, which will cause your lawn to begin growing too early. If you’re trying to control weeds, it’s best to apply your herbicides separately from fertilizer, anyway.

In North Florida, it’s best to wait until your lawn has completely greened up in spring before applying any fertilizer.

Waiting allows for more efficient use of the fertilizer. You will not injury you lawn by waiting to fertilize but you can certainly injure your lawn by fertilizing too early.

So, have patience, allow your lawn to green up on its own and then fertilize, even if it’s not until mid April or May.

Larry Williams, UF/IFAS Extension Agent, Okaloosa County, March 5, 2015