Why has my grass seed not come up?

The four things that stop grass seed germinating — soil temperature, moisture, seed-to-soil contact and birds — and how to tell which one you have.

Difficulty: beginner
Time: 30 min
Read: 3 min

Short answer

Grass seed needs soil above about 8C and constant surface moisture for two to three weeks. Sown too early, allowed to dry once, or left sitting on top of firm soil, it will not come up. Check the soil temperature and whether the seed is actually in contact with soil.

Germination times vary by species: ryegrass can appear in seven days, fescues and bents often take three weeks. Judging failure too early is common, so give it the full time before concluding anything.

What you'll need

Rake
Watering can or sprinkler
Netting or fleece if birds are a problem

Step by step

Give it long enough.Ryegrass in about a week, fescue and bent mixtures up to three weeks, and longer in cool weather. Do not resow at day ten.
Check the soil temperature.Below about 8C nothing happens. In the UK that usually means mid-April to early June, or September, rather than March or midsummer.
Check whether it ever dried out.A germinating seed that dries once is dead. The surface must stay damp continuously, which in warm weather means watering lightly twice a day.
Check seed-to-soil contact.Scratch the surface. If seed is sitting on top of firm soil or on dead thatch, it has nothing to root into. Rake it in lightly so it is just covered.
Look for bird damage.Seed disappearing rather than failing means birds. Netting, fleece or a light cover of sieved soil solves it.
Rule out weedkiller and feed residue.Most lawn weedkillers and some feeds prevent germination for weeks. Check what was applied and when — many need a clear interval before sowing.
Check the seed is not old.Grass seed loses viability after a couple of years, particularly if stored in a damp shed. Fresh seed is cheap relative to the effort of sowing.
Resow at the right time.Prepare a fine, firm, weed-free surface, sow at the rate on the pack, rake in, firm gently and keep damp. Autumn sowing in the UK usually beats spring for reliability.

Tips

Soil temperature, not air temperature, decides germination.
One dry afternoon at the wrong moment kills a whole sowing.
Seed that has vanished rather than failed is birds — cover it next time.

Common mistakes

Sowing in March because the weather feels mild — Air warms long before soil does. Seed sown into cold soil sits there, rots or gets eaten, and the failure is blamed on the seed.
Watering heavily once a day — A heavy soak washes seed into drifts and then the surface dries. Light, frequent watering keeps the top few millimetres damp, which is where the seed is.

If it doesn't work

Nothing after three weeks in warm damp conditions

Cause: Old seed or weedkiller residue — Fix: Test a pinch on damp kitchen paper indoors. If it germinates there, the ground is the problem.

Patchy germination in drifts

Cause: Heavy watering moved the seed — Fix: Water lightly and often, and overseed the bare drifts.

Seed visibly gone

Cause: Birds — Fix: Resow and cover with fleece or netting until the seedlings are up.

Germinated then died

Cause: Dried out, or seedlings mown too early — Fix: Keep damp until after the second mow, and set the first cut high.

Questions people ask

When is the best time to sow grass seed in the UK?

Early September is the best window — warm soil, reliable rain and few weeds competing. Mid-April to May is the second best. Midsummer and winter both fail.

How long does grass seed take to germinate?

Ryegrass around seven to ten days, fescue and bent mixtures up to three weeks, and longer if the soil is cool. Judge nothing before the full period has passed.

Do I need to cover the seed?

Rake it in so it is just covered by a few millimetres of soil. Deeper than that and it will not reach the light. A cover of fleece helps against birds and drying.