Flushing and killing weeds (false seedbed)
A former field or weedy plot is full of weed seed. Sprout it and kill it before you sow, so the grass does not lose the race.
- When
- In order, while the lawn is being made
- For
- Any lawn
- Rule
- est-weed-flush · Hessayon; RHS; Regional
A former field or weedy plot is full of weed seed. Water the bare, level soil for 1–2 weeks to sprout that seed, then kill the flush before you plant — so the new grass doesn't lose the race to weeds.
Why bother
Every cultivated soil holds a bank of weed seed, and tilling brings fresh seed to the surface. Sow grass straight away and the weeds come up with it, often faster. A false (stale) seedbed lets them germinate first so you can remove them before the grass is in.
How
- Prepare and level the bed as if you were about to sow.
- Water it, or wait for rain, and leave it for one to two weeks in warm weather. A flush of small green seedlings appears.
- Kill the flush while the seedlings are tiny: hoe very shallowly on a dry, sunny day, or use a suitable non-residual weedkiller and wait the period its label specifies before sowing.
- Do not dig or till again; that brings up a new layer of seed.
- Repeat once on very weedy ground, then sow.
Timing
This adds two to four weeks, so plan it into the schedule. For an early-autumn sowing, start the flush in mid to late August.
A residual pre-emergent weedkiller is not a substitute: it would stop the grass seed too.
Do this first
Sources
- D.G. Hessayon — The Lawn Experthessayon
- Royal Horticultural Society — lawn guidancerhs
- Regional practice — continental climate, zone 7regional