Best Starter Fertilizer for New Grass Seed & Sod

Whether you’re overseeding thin spots, establishing a brand new lawn from seed, or laying fresh sod, a starter fertilizer gives your new grass the nutrient boost it needs to develop strong roots fast. Starter fertilizers are formulated differently than regular lawn fertilizers — they’re higher in phosphorus, which is the nutrient most directly responsible for root growth in young plants.

Skip the starter fertilizer and your new grass will germinate fine, but root development will be slower, establishment will take longer, and the grass will be more vulnerable to drought and heat before it’s fully anchored. Spend $15–$25 on the right starter and you’ll see the difference within weeks.

What Makes Starter Fertilizer Different

The three numbers on any fertilizer bag (like 18-24-12) represent the ratio of nitrogen (N), phosphorus (P), and potassium (K). Regular lawn fertilizers are heavy on nitrogen (the first number) because established grass uses nitrogen for leaf growth and green color. Starter fertilizers flip the emphasis — they’re proportionally higher in phosphorus (the middle number) because new seedlings and sod need to build root mass first.

Typical starter fertilizer ratios include 18-24-12, 10-18-10, and 12-25-12. The common thread is that the phosphorus number is the highest or very close to it. Once the grass is established (usually 6–8 weeks after seeding or 3–4 weeks after sodding), you switch to a regular maintenance fertilizer with a higher nitrogen ratio. Our guide on how often to fertilize your lawn covers the long-term schedule.

Important note on phosphorus restrictions: Some states and municipalities restrict the use of phosphorus in lawn fertilizers to protect waterways. However, most of these regulations include an exception for starter fertilizer when establishing new turf. Check your local regulations, but in most cases, applying a phosphorus-containing starter fertilizer to new seed or sod is both legal and recommended.

Our Top Picks

1. Scotts Turf Builder Starter Food for New Grass — Best Overall

Price: Around $20–$25 (covers 5,000 sq ft) | NPK ratio: 24-25-4

Scotts Starter is the most widely available and best-selling starter fertilizer in the country. The 24-25-4 formula delivers a high dose of both nitrogen and phosphorus, promoting both root growth and early green-up simultaneously. It’s designed to be applied at the time of seeding or sodding and won’t burn new grass when used at the label rate.

The application process is simple: spread it with a standard broadcast spreader right after putting down seed (or just before laying sod), then water it in. Scotts provides specific spreader settings for every Scotts spreader model right on the bag. If you’re using a different brand of spreader, our guide to how grass spreads can help you understand why even distribution matters so much at this stage.

Best for: Most homeowners establishing new lawns or overseeding. Reliable, easy to find, and proven effective.

2. Scotts Turf Builder Starter Food for New Grass Plus Weed Preventer

Price: Around $25–$35 (covers 5,000 sq ft) | NPK ratio: 21-22-4 + mesotrione

This is a two-in-one product that combines starter fertilizer with mesotrione, a pre-emergent herbicide that prevents crabgrass and other weeds from germinating alongside your new seed. The key selling point is that mesotrione is one of the very few pre-emergent active ingredients that won’t inhibit grass seed germination — most pre-emergents stop all seeds, including the ones you just planted.

This is particularly valuable for fall overseeding when annual weeds like crabgrass may still be germinating, or for spring seeding when weed pressure is highest. Note that this product is NOT for use with all grass types — check the label for compatibility with your specific grass.

Best for: Spring overseeding or any new seeding where weed pressure is a concern.

3. Jonathan Green Green-Up Starter Lawn Fertilizer

Price: Around $25–$30 (covers 5,000 sq ft) | NPK ratio: 12-18-8

Jonathan Green’s starter formula takes a more balanced approach with a 12-18-8 ratio that includes meaningful potassium alongside the phosphorus. Potassium strengthens cell walls and improves stress tolerance, which is valuable for new grass that’s still fragile. The lower nitrogen content reduces the risk of burning tender seedlings — useful if you tend to be heavy-handed with the spreader.

This is a good choice if you’re using Jonathan Green’s Black Beauty seed, as the products are formulated to work together, but it works equally well with any grass seed brand.

Best for: Homeowners who want a gentler, more balanced starter with added potassium for stress resistance.

4. Milorganite 0620 Organic Nitrogen Fertilizer

Price: Around $12–$18 (covers ~2,500 sq ft) | NPK ratio: 6-4-0

Milorganite isn’t technically marketed as a starter fertilizer, but it’s a favorite in the DIY lawn care community for new seedings. It’s an organic, slow-release nitrogen source made from heat-dried microbes. The 6-4-0 ratio is lower in phosphorus than dedicated starters, but because it releases nutrients very slowly, there’s zero risk of burning new seedlings — even if you over-apply.

Many experienced lawn enthusiasts use Milorganite in combination with a high-phosphorus starter: apply the Scotts Starter at seeding time for the initial phosphorus boost, then follow up with Milorganite 3–4 weeks later for a gentle, sustained nitrogen feed as the young grass transitions into active growth.

Best for: Organic lawn care enthusiasts, or as a secondary application 3–4 weeks after seeding alongside a traditional starter.

How to Apply Starter Fertilizer

For new seed: Apply starter fertilizer immediately after spreading seed, then water both in lightly. The fertilizer and seed can go down in either order — some people prefer to put the fertilizer down first and seed on top, while others do the reverse. The result is the same as long as both are watered in.

For new sod: Apply starter fertilizer to the bare soil before laying the sod. This puts the phosphorus right where the roots will be reaching for it. Water the sod thoroughly after installation.

For overseeding: Apply immediately after overseeding your existing lawn. The existing grass won’t be harmed by the starter formula — it just gets a nutrient bonus. For more on the overseeding process, see our guide on reseeding over dead sod.

Application rate: Follow the rate printed on the bag — typically 4–6 lbs per 1,000 sq ft for most granular starters. More is not better with fertilizer. Exceeding the label rate can burn new grass and waste money. Our article on how much sod is in a roll can help you calculate your area if you’re laying sod.

When to Switch to Regular Fertilizer

After 6–8 weeks, your new grass should be established enough to mow regularly and withstand normal foot traffic. At that point, switch to a standard maintenance fertilizer with a higher nitrogen ratio (like 24-0-6 or 16-4-8). Continue with your regular fertilizer schedule from there — our fertilizing frequency guide has the full breakdown by grass type and season.

Bottom Line

Scotts Turf Builder Starter Food for New Grass is the safe, proven recommendation for most homeowners — effective, affordable, and available everywhere. The weed preventer version is worth the upgrade if you’re seeding in spring when weed pressure is high. For a more balanced organic approach, pair Milorganite with a phosphorus-rich starter. And remember: starter fertilizer isn’t optional. It’s one of the cheapest investments you can make for the long-term success of new grass.