9 FAQs About Applying Starter Fertilizer to Your Lawn

lawn fertilizing

Whether you are planting new grass from scratch or repairing bare spots, figuring out a proper fertilizer to get your grass off to the best start can be daunting. One look at your local garden center’s fertilizer aisle and you’re inundated with choices for producing your vibrant lawn.

We’ve taken the mystery out of starter fertilizers for lawns, including how and when to use them, why they are beneficial and why you might not need to use one. With these nine FAQs about using starter fertilizer on your lawn, we’ll also explain what all those numbers on the fertilizer package mean and how they’ll affect the growth of your grass.

Our Top Picks for Starter Fertilizers:

1. What is a lawn starter fertilizer?

Starter lawn fertilizer helps your grass seedlings and sod roots establish rapidly in the soil, leading to a thick new lawn in a short period. Although various starter fertilizers for grass may differ slightly in composition, they all give the grass seeds and new sod the nutritional boost required for healthy germination and rapid root growth. They will usually have equal amounts of nitrogen, phosphorous and potassium. However, some types contain two parts of nitrogen and one part of phosphorous and potassium. There are both slow-release and quick-release formulations, with the latter delivering a quick green-up dose of nitrogen. It can be applied to all-new lawns, or to help bare spots recover.

2. What is a good starter fertilizer for grass seed and sod?

Starter fertilizers for lawns come in different compositions of the primary nutrients nitrogen (N), phosphorous (P-phosphate) and potassium (K-potash), or the three numbers listed on the package (NPK). The numbers list the percentage of each nutrient contained in the starter fertilizer for grass. For example, a fertilizer ratio of 10-10-10 contains 10 percent of nitrogen, phosphorous and potassium.

When it comes to the specific job of each of these primary nutrients in regards to the health of your turf:

  • Nitrogen: Is required for satisfactory growth and green coloration.
  • Phosphorous: Plays an important role in various growth processes including good root development.
  • Potassium: Promotes good disease resistance, tolerance of drought and winter hardiness in turfgrass.

Some examples of the formulations of common starter fertilizers for lawns are 10-10-10, 20-10-10 and 16-8-8. Penn State Extension notes that analyses of 15-10-10 or 10-6-4 are also acceptable used as starter fertilizers for grass, as they also promote good early growth and grass development.

3. Should you apply a starter fertilizer to both grass seed and sod?

Peter Landschoot, Ph.D., professor of turfgrass science at Penn State Extension states, “Yes, both seed and sod. Seedling grasses need greater amounts of nitrogen and phosphorus than mature grass plants because seedlings are producing new tissues rapidly and thus have higher energy and nutrition requirements.” Reseeding a lawn will take more time, but sod will be more expensive. “Even though sod is mostly composed of mature turf, many of the roots have been severed during the harvesting operation,” Landschoot says. Some nitrogen and phosphorus (as starter fertilizer) applied to the soil before the sod is laid should help hasten development of new roots.”

4. Is it best to get a soil test first to see phosphorus levels?

Soil test

Landschoot notes, “Because soil-test levels of phosphorus don’t change much over short periods, you can collect soil samples and submit to a test lab to determine phosphorus levels within a year of establishing turf. Soil samples can be collected any time during the year as long as soil is not frozen. The ideal situation would be to collect soil and submit the sample(s) to a test lab as close to the time of establishment as possible. Just be sure to allow time for the lab to process the samples and return your report with phosphorus recommendations. Also, build in a few days to interpret the report and purchase the correct amount and type of fertilizer.”

5. Is there a standard amount of starter fertilizer I should use?

If you didnít get a soil test to determine how much starter fertilizer for the lawn you should use, Landschoot writes, “Starter fertilizers should be applied at 0.5 to 1 lb. nitrogen per 1,000 sq. ft. Amounts in excess of 1.5 lb. nitrogen per 1,000 sq. ft. can burn the young turf and result in poor establishment. Application of a starter fertilizer is not a substitute for the phosphate and potash recommended on your soil test report.”

6. Are there circumstances where you shouldn’t use a starter fertilizer?

When it comes to situations where a starter fertilizer for grass isnít required, Landschoot advises, “In some cases, a 1- or 2-inch layer of good quality compost amended into soil before establishing turf will provide more than enough nitrogen and phosphorus for optimum establishment. This is certainly the case with bio-solids or manure-based composts which contain significant amounts of nitrogen and phosphorus, so a starter fertilizer is not needed.”

You should not use starter fertilizer in areas where you cannot control runoff. Nitrogen and phosphorus from indiscriminate use of fertilizers have caused such great environmental concerns that about half the states in the U.S. have imposed some sort of regulations on fertilizer use.

If your lawn is not rich in natural organic matter, nitrogen plays an important role. Addressing soils that aren’t amended with organic materials Landschoot continues, “In cases where soils are not amended with compost, nitrogen is almost always needed for rapid establishment. Our research shows a greater influence of nitrogen compared to phosphorus on the rate of turf establishment, so if you can’t use phosphorus (or you think there is enough phosphorus in the soil), an application of 1 lb. quick-release nitrogen per 1,000 sq. ft. will speed up seedling development.”

When it comes to explaining phosphorus and its role Landschoot also notes, ‘”Phosphorus is included in starter fertilizer primarily to enhance root development. Some research shows little influence of phosphorus on turf establishment in soils containing adequate to high levels of soil-test phosphorus; whereas other studies show benefits even when phosphorus levels are adequate. Generally, developing seedlings growing in compact soils during cold temperature periods are thought to benefit more from phosphorus in starter fertilizer.î

7. When should starter fertilizers be applied?

When applying a starter fertilizer, itís best to apply before seeding or before laying sod, or after you plant your grass seed. You donít want to apply it directly to newly planted sod or burning can occur. In fact, you should wait six to eight weeks before applying another dose of balanced fertilizer to your grass after planting so it doesnít incur burning.

When it comes to knowing how much starter fertilizer for the grass youíll need, Penn State Extension suggests taking a soil test. The test will note just what nutrients require beefing up in the soil to benefit your turfís growth and how much is required. The three most important nutrients required for good growth and health of your turfgrass are nitrogen, phosphorous and potassium, which a starter fertilizer contains.

There are benefits to incorporating the starter fertilizer into the soil before planting. When phosphorous and potassium are applied only to the surface of the soil they cannot move down into the soil fast enough. In addition, nitrogen can easily be leached from the soil before the grass even has a chance to uptake its nutrients. Therefore, itís best to till into the soil 4 to 6 inches with any additional amendments you are adding. However, if you desire, you can spread the starter fertilizer over the site immediately after spreading your grass seed.

8. Can I use a starter fertilizer for grass that is established?

Probably not. Although you can use a starter fertilizer for a lawn that is established, it’s better to use a well-balanced fertilizer designed specifically for grass that is established. The starter fertilizer might not contain all the required nutrients for continued growth and good health. It won’t hurt the grass, but might lack the needed nutrients that a well-balanced fertilizer for continued lawn maintenance contains.

9. How should starter fertilizer be applied?

Once you’ve received your soil test, selected an appropriate starter fertilizer for your soil and know the needed amounts, applying it over the lawn area is relatively basic. Just pour the required amount into a standard fertilizer spreader and evenly apply the starter fertilizer over the planting site. Once applied, work the product 4 to 6 inches into the soil, if you are planting grass seed or sod after the application. If you are applying the product after you apply grass seed, spread the product over the soil and water into the soil.

When it comes to using a starter fertilizer for new sod or grass seed, thereís a definite benefit to its use to promote the healthiest growth and establishment of your lawn in the quickest amount of time. Of course, donít go overboard with its use and think more is better. As with many things in life, too much of a good thing can be bad and too much starter fertilizer for your developing lawn can affect it negatively through burning. A soil test takes the mystery out of what your soil lacks and lets you know what strength of starter fertilizer your grass requires and how much. Used properly, it won’t be long before your bare feet are enjoying the feel of your healthy lawn.

Joyce Starr

Joyce Starr

Joyce Starr has been writing on horticultural and landscaping topics for over 15 years. In addition, for the past 20 years she’s owned and operated a landscaping and design business. She shares her experience and passion for all things green through her writing.