Choosing Lawn Fertilizer
Fertilize all turfgrasses except centipede. For the fall feeding choose an all-purpose or a “winterizer” lawn fertilizer. They have proportionately less nitrogen and more of the nutrients that promote root development. In the spring choose a slow acting granular lawn fertilizer that has 25 to 30% of its nitrogen in slow-acting or water insoluble (WIN) form. This way the nitrogen is delivered to grass plants slowly and consistently over several weeks, rather than in relatively large doses within a week or two. Depending on the amount of slow-release nitrogen in the product, it may last from 8 to 16 weeks.
Look for a package label that says the product is for lawns and is slow-acting. Do not worry about the three numbers which detail the ratio of nitrogen, phosphorus and potassium (NPK ratio) in the particular product unless you have a special situation. Check how much area the bag covers and buy enough to do your entire lawn. Avoid fertilizers that are combined with weed or insect killers. These problems should be addressed separately.
When to Fertilize
Grass growing in good soil with lots of organic material in it, needs fertilizing only once or twice a year. Fall is the best time in the South if you choose to do it only once. However, if your lawn is typical of most in this country, your grass is struggling to grow in infertile, compacted soil with little or no organic material in it to provide nutrients.
So it is best that you fertilize 2 or 3 times--once in the spring, again in the early summer, and finally in the fall. The summer feeding is optional, especially if you use a slow-acting type in the spring that lasts up to 10 weeks. Perform the spring feeding as soon as the grass starts to grow. Never fertilize a lawn that is stressed by drought, disease or insect infestation.
Providing Snacks and Vitamins
If your grass is dense, mowed to the correct height, and growing in soil with lots of organic material, the main meals of granular, slow-acting fertilizer in the spring and fall are sufficient. It should be green and gorgeous all season long. If your grass is growing in poor soil, then you may want to provide an occasional snack in addition to the main feedings to boost plant vigor.
Supplement the spring meal by spraying a very dilute liquid lawn fertilizer snack on a warm season lawn with a hose end sprayer on your garden hose in late June. Better yet, a snack of a plant tonic , a liquid seaweed or kelp-based product, in late June or early July boosts drought, insect and disease resistance as the grass goes into the heat of summer. These tonics are not fertilizers, but provide minerals and hormones and other ingredients that help stressed grass plants grow better. Snacks are optional, but they do make a difference.