Best grass seed

A seed bag tells you how many square feet it covers. An extension service tells you how many pounds a species needs per thousand square feet. Those are the same fact in different units, and converting one into the other is the only way to tell whether you are buying seed or buying coverage claims.

The short answer

Coverage claims, converted

Each maker publishes a bag size and the area it covers. Divide and you get a rate.

Every bag size in the Jonathan Green range — 1, 3, 7, 25 and 50 lb — returns the same two rates, which tells you the coverage table was calculated from a rate rather than estimated bag by bag. That is a small sign of a seriously kept specification.

What the extension rates say about those numbers

Penn State Extension publishes seeding rates per 1,000 sq ft by species: Kentucky bluegrass 2-3 lb, perennial ryegrass 4-5 lb, turf-type tall fescue 6-8 lb, fine fescues 4-5 lb.

Read the two bags against that table and something interesting falls out. Jonathan Green's mix is tall-fescue based, and its 5 lb per 1,000 sq ft new-lawn rate is below the 6-8 lb PSU gives for tall fescue — the bluegrass and ryegrass in the blend pull the average down, because both are seeded at lower rates. Scotts' 7.5 lb sits above the range for every species in its own blend. Neither is wrong; blends are seeded by count as much as by weight, and seed size differs enormously between species. But it does mean the Scotts bag buys you fewer square feet per pound, and now you know by how much.

The two, on published figures

1. Jonathan Green Black Beauty Ultra — best coverage per pound

A tall-fescue-based mix with Kentucky bluegrass and perennial ryegrass, sold in everything from a 1 lb patch bag to a 50 lb reseed. Germination is published as 7-14 days, shade tolerance is rated excellent, and the light requirement is stated plainly as 6+ hours of sun per day — a useful piece of honesty in a category where "shade mix" often implies no sun is needed at all.

At 5 lb per 1,000 sq ft for a new lawn, a 25 lb bag does 5,000 sq ft. That is a third less seed per square foot than the alternative here.

What it does not publish: the percentage split between the three species, or any cultivar names. Tall fescue also has a coarser leaf than a bluegrass lawn, which is a look you either want or do not.

#ad Check the Jonathan Green Black Beauty Ultra Grass Seed price on Amazon — how we're funded.

2. Scotts Turf Builder Sun & Shade — best species disclosure

Five species named on the bag — Kentucky bluegrass, perennial ryegrass, creeping red fescue, chewings fescue and hard fescue — plus a 4-0-0 analysis, a fungicide seed treatment against damping-off in a wet spring, and a seeding window published as air temperatures consistently between 60F and 80F.

Three of those five are fine fescues, which is what makes it a shade mix: fine fescues tolerate low light better than bluegrass does. It is also what limits it, because fine fescues are the least wear-tolerant grasses in a cool-season lawn.

The cost is rate. 7.5 lb per 1,000 sq ft on a new lawn is 50% more seed than the Jonathan Green mix asks for, so compare bags by area covered rather than by weight.

#ad Check the Scotts Turf Builder Grass Seed Sun & Shade Mix price on Amazon — how we're funded.

Timing, depth and the part people get wrong

Penn State Extension is direct about when: "late summer is the optimum time to seed in most areas of Pennsylvania," because soils are drier and warmer in late August and early September than in spring. The same page describes covering seed by dragging the area so that most seeds end up under about a quarter inch of soil.

Who should skip both

• Warm-season lawns. Both mixes are cool-season. In bermudagrass, zoysia or St. Augustine country they will not persist through summer — see grass types guide.
• Deep shade under mature trees. Shade tolerance is relative. Below about four hours of light, no seed mix produces a lawn — see moss and shady lawns.
• Anyone who has not tested the soil. Seeding into soil with a pH or phosphorus problem wastes the bag. A soil test costs less than the seed.

What we cannot tell you

We have not grown either mix out. Neither maker publishes the percentage split between species, cultivar names, purity and germination percentages from a seed analysis tag, or a weed seed content figure — all of which are printed on the physical tag and none of which appear on the product pages. Jonathan Green publishes no seed treatment and no analysis; Scotts publishes no light requirement in hours. We have transcribed what each one prints and converted it to a common unit; the rest is on the bag in the store.