3-18-18 Liquid Starter Fertilizer for New Grass and Overseeding (2026)
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New seed, sod, and plugs do not need a green-up feed, they need roots. That is what a 3-18-18 starter fertilizer delivers: low nitrogen so you are not pushing top growth before the lawn is anchored, and high phosphorus and potassium to drive root establishment. Here is how to use it for a new lawn and as a fall hardiness feed on an established one.
For where a starter fits among the other liquids, see our best liquid lawn fertilizer guide.
Why low nitrogen, high phosphorus and potassium
A starter ratio flips the usual priorities. The low first number means little nitrogen, because pushing leaf growth on a lawn that has not rooted yet leaves it weak and prone to drying out. The high middle and last numbers, phosphorus and potassium, are what build the root system and the stress tolerance a new lawn needs to survive its first weeks. That is why a 3-18-18 is the right call for seeding, sodding, and plugging.
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.
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