Best lawn fertilizer

Fertilizer is the one lawn purchase where the arithmetic is genuinely important. Put down too much nitrogen in one pass and you burn the lawn and feed the storm drain. The bag tells you everything you need to avoid that — if the maker publishes both halves of the sum.

The short answer

Bag coverage converted to nitrogen

Two published figures — the bag weight and the area it covers — give you pounds of product per 1,000 sq ft. Multiply by the analysis and you have pounds of nitrogen, which is the number the Extension guidance is written in.

The three, on published figures

1. Jonathan Green Veri-Green — the documented rate

Twenty-nine percent nitrogen, 40% of it slow release from polymer-coated urea, 4% iron for color, no phosphate at all, and a published three-month feed. The 15 lb bag covers 5,000 sq ft, which is 3 lb of product and 0.87 lb of nitrogen per 1,000 sq ft.

Publishing the slow-release share as a percentage is the unusual part. It is the figure that separates a fertilizer that feeds for months from one that dumps everything in a fortnight, and almost no consumer bag states it.

The honest caution: at a 29% analysis, a miscalibrated spreader or a double pass shows up as a burn stripe. Calibrate first — the method is in spreader settings.

#ad Check the Jonathan Green Veri-Green Nitrogen Rich Lawn Fertilizer (29-0-3) price on Amazon — how we're funded.

2. Milorganite — the low-burn option

A 6-4-0 analysis with 2.5% iron, feeding 8 to 10 weeks, in a 32 lb bag rated for 2,500 sq ft. The low analysis is the feature: at 12.8 lb of product per 1,000 sq ft you are spreading four times the bulk of a high-analysis bag, and a spreader error costs you proportionally less.

It also carries the most iron-to-nitrogen of the three, which is the combination that produces color without pushing growth you then have to mow.

Two cautions. It contains 4% phosphate, which several states restrict on established lawns unless a soil test calls for it — test first, with our soil testing guide. And 12.8 lb per 1,000 sq ft means carrying a great deal more product for the same lawn.

#ad Check the Milorganite Slow-Release Nitrogen Fertilizer (6-4-0) price on Amazon — how we're funded.

3. Scotts Turf Builder — easiest to buy, hardest to verify

A 32-0-4 analysis, bags covering 5,000 and 15,000 sq ft, an application frequency of every 6 to 8 weeks up to four times a year, and shelf presence almost everywhere. For a lawn that needs nitrogen and nothing else, the analysis is right.

What Scotts will not tell you is how much nitrogen it puts down. Its product page publishes the coverage and the analysis but not the bag weight, so the middle term has to come from the retailer: the 15,000 sq ft listing states 37.50 lb, which works out to 2.5 lb of product and 0.80 lb of nitrogen per 1,000 sq ft. That is a usable figure and a weaker source than the other two bags on this page, both of which publish their own weights.

Four applications a year at an unverifiable rate is also the pattern most likely to over-fertilize a lawn that never needed it. Start with a soil test, not a schedule.

#ad Check the Scotts Turf Builder Lawn Food (32-0-4) price on Amazon — how we're funded.

Who should skip all three

• Anyone who has not tested the soil. Fertilizer is a prescription, not a routine. A test costs less than a bag and tells you which of these three, if any, your lawn wants.
• Lawns beside water. Broadcast fertilizer near a pond, stream or storm drain needs a drop spreader and a deflector, or a different plan entirely.
• Anyone mulching clippings already. Returned clippings supply the equivalent of roughly one application a year on their own — see clippings and composting.

What we cannot tell you

We have not applied these products or measured a response. Scotts publishes no bag weight, no feeding duration and no slow-release share. Milorganite publishes no slow-release percentage and no rate per 1,000 sq ft on its specification page. None of the three publishes a burn-risk threshold, a temperature limit for application, or a figure for how much nitrogen leaches on sandy soil — all of which are real, and none of which a bag will tell you.