3-18-18 Liquid Starter Fertilizer for New Grass and Overseeding (2026)

The pick: Simple Lawn Solutions Ultimate 3-18-18

For a liquid starter, Simple Lawn Solutions Ultimate 3-18-18 covers both jobs. The high phosphorus and potassium drive establishment on new grass, and on an established lawn that a soil test shows is low in phosphorus or potassium, the same ratio works as a late-season hardiness feed without a nitrogen surge. It sprays on through the attached hose-end sprayer like the rest of the line.

How and when to apply it

For new seed or sod, apply at planting and again a few weeks later as the lawn establishes, keeping the soil consistently moist through germination and rooting. For fall hardiness on a mature lawn, apply in late summer to early fall as growth slows. Either way, follow the label rate and use the fertilizer calculator to size the application. One caution: if you used a soil-loosener or any product that can affect germination, check its label for timing before seeding.

Frequently asked questions

• What is 3-18-18 fertilizer used for? Establishing new grass from seed, sod, or plugs, where the high phosphorus and potassium build roots, and as a fall hardiness feed on established lawns.
• Why is the nitrogen so low in a starter fertilizer? Because pushing leaf growth before the lawn has rooted leaves it weak. A starter prioritizes roots first, top growth later.
• Can you use 3-18-18 on an established lawn? Use it for late-season root strength and winter hardiness only when a soil test shows phosphorus or potassium is low, since most established lawns already have enough phosphorus and some areas restrict it. For routine color, use a balanced 16-4-8 instead.
• When should you apply a liquid starter? At planting for new grass, with a follow-up a few weeks later, or in late summer to fall for hardiness on an established lawn.

For the full lineup ranked by need, see the best liquid lawn fertilizer guide.