How to Look After a Lawn

Lawn care is full of numbers printed on bags, and almost none of them are the number you actually apply. Seed rate belongs to the grass, fertilizer is measured in nitrogen rather than fertilizer, and watering is measured in inches rather than minutes.

Here is what each tool is really telling you.

Seed: the rate belongs to the grass

The Grass Seed Calculator handles the fact that seed is sold by weight but applied by rate, and the rate depends on the species.

The example worth remembering: bluegrass goes down at about a quarter of the fescue weight — and delivers twice the seeds. Bluegrass seed is tiny, so a pound of it is an enormous number of seeds. Applying fescue's rate of bluegrass is not generous, it is a dense mat that thins itself out through competition.

Look up the rate for what you are actually sowing. This is the one place where "a bit extra" does real harm.

Sod: it is alive and on a clock

The Sod Calculator gives area and pallet count, and flags the constraint no other material has: sod is alive.

Everything else in these guides can sit in a garage until the weekend. Sod cannot. It is harvested, stacked and delivered, and it starts declining immediately — heating in the middle of the pallet in warm weather. Ordering the right amount matters much less than having the ground prepared before it arrives.

Prepare first, then order. Not the other way round.

Fertilizer: you apply nitrogen, not fertilizer

The Lawn Fertilizer Calculator carries the single most misread number in lawn care: you apply pounds of NITROGEN, not pounds of fertilizer.

Worked through: a 16-4-8 bag needs 6.25 lb of product to deliver 1 lb of nitrogen. That ratio is the calculation. Someone applying "one pound of fertilizer per thousand square feet" because a guide said one pound of nitrogen is putting down roughly a sixth of what they think.

The first number on the bag is a percentage. Everything follows from that.

Water: an inch, measured with a tin

The Lawn & Garden Watering Calculator converts the advice ("an inch a week") into something you can act on: an inch of water over 1,000 sq ft is 623 gallons.

Then it tells you how to check — measure your sprinkler's real output with a tuna can. Put straight-sided tins around the lawn, run the sprinkler, and see how long it takes to fill one to your target depth.

Do this once. Sprinkler output varies enormously by pressure, head type and how far along the hose you are, so a timer set from a manufacturer's figure can be out by a factor of two — and you will never know which way.

Topsoil: it settles

The Topsoil Calculator gives cubic yards and tons, with a settling allowance — because topsoil delivered loose loses roughly a fifth of its depth once it beds in.

Order to the settled depth you want, not the depth it looks like on delivery day.

The short version

1. Seed rate depends on the species — bluegrass is a quarter of fescue by weight.
2. Prepare the ground before sod arrives. It is on a clock.
3. Fertilizer is measured in nitrogen. A 16-4-8 needs 6.25 lb for 1 lb of N.
4. An inch over 1,000 sq ft is 623 gallons. Check your sprinkler with a tin.
5. Order topsoil about a fifth over your finished depth.

Each has a printable, and the fertilizer sheet is the one worth keeping in the shed — the percentages on the bag change every time you buy a different product.