How to plant grass seed: timing, seeding rates and watering for a new lawn

Planting grass seed works best when three things line up: the right season for your grass type, good seed-to-soil contact, and steady moisture until the seedlings are established. Get those right and the rest is routine.

Start by measuring the area with our lawn area calculator — seeding rates are given per 1,000 square feet, so you need the size before you buy.

1. Pick the right time

It depends on whether you grow cool-season grasses (Kentucky bluegrass, tall fescue, perennial ryegrass, fine fescues — common across the northern half of the US) or warm-season grasses (Bermudagrass, zoysia, St. Augustine, centipede — common in the South).

• Cool-season grasses: late summer to early fall is the ideal time. University of Illinois Extension gives early August to early September for northern Illinois, mid-August to mid-September for central Illinois and September for southern Illinois. April is the second choice; seeding from late spring through mid-summer often struggles because summer heat slows the young grass.
• Warm-season grasses germinate and grow when soils are warm, so they are generally planted from late spring into early summer. Check your state’s land-grant university extension for local dates.

2. Choose seed and work out how much to buy

Buy seed suited to your region, sun and use. Read the label: it lists the species, the germination percentage and the weed seed content.

Seeding rates from University of Illinois Extension, in pounds per 1,000 sq ft:

Seed	Rate
Kentucky bluegrass blend	1–3 lb
Kentucky bluegrass / perennial ryegrass mix (80:20)	3–4 lb
Kentucky bluegrass / fine fescue mix (50:50)	3–5 lb
Tall fescue blend	6–9 lb

Follow the rate on your bag if it differs. More is not better: going over the rate can produce weak, spindly seedlings and encourage disease.

Example: a 2,500 sq ft front yard with a tall fescue blend at 7 lb per 1,000 sq ft needs 2.5 × 7 = 17.5 lb of seed.

3. Prepare the soil

• Remove existing weeds, stones and debris.
• Loosen compacted soil and rake it level, filling low spots so water does not pool.
• A soil test (many extension offices offer one) tells you whether lime or fertilizer is needed before seeding.
• Finish with a firm, fine surface — loose fluffy soil dries out quickly and leaves footprints that become dips.

4. Sow in two directions

1. Set your spreader for half the seeding rate.
2. Sow the whole area walking east–west, then sow the second half walking north–south. This avoids stripes and bare patches.
3. Drag a leaf rake lightly over the surface so the seed is in contact with the soil, but not buried deep.
4. Spread a light straw mulch — Illinois Extension suggests about one bale per 1,000 sq ft. It slows drying and keeps soil and seed from washing away.

5. Water little and often — then deeper

• Until the seed germinates, keep the top layer of soil constantly moist. That usually means light watering one or more times a day in warm, dry weather.
• Once the seedlings appear, water deeper and less often, so the roots grow down.
• Use a gentle spray so the seed is not washed into puddles. Our irrigation water calculator helps estimate how much water a given area needs.

6. First mowing

Mow for the first time when the grass is about 3 to 3½ inches tall, with a sharp blade and when the soil is dry enough not to rut. Keep foot traffic light for the first few months.

Common mistakes

• Seeding at the wrong time of year for the grass type — the most common cause of failure.
• Letting the seedbed dry out for a single hot afternoon during germination.
• Burying seed too deep or leaving it sitting on top of hard ground.
• Sowing far more seed than the label says.
• Using weed killers on a new lawn without checking the label: many are not safe for seedlings.

Quick checklist

• Area measured and seed amount calculated
• Seed suited to region, sun and shade
• Soil cleared, loosened, leveled and firmed
• Seed spread in two directions and raked in
• Light straw mulch applied
• Watering plan for the next three to four weeks