PlantSowGrow
How to grow Mustard (Green Manure)
Sinapis alba
The fastest green manure: a dense, bright-green cover in weeks that smothers weeds before winter. Avoid where clubroot is a problem — it is a brassica.
At a glance: Sow mid July to late September, harvest from late August.
When to sow, plant and harvest
Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.
Growing Mustard (Green Manure): what it needs
- Light
- Full sun · 4+ hours a day
- Watering
- No watering needed once established
- Soil
- Any soil
- Spacing
- Broadcast thinly
- In pots
- Best in the ground
- Feeding
- No feeding needed
- Hardiness
- USDA zones 3–9
- Difficulty
- Easy
Step by step
- Mid July – late September · 13 weeks after the last spring frost
Sow on Bare Ground
Rake the soil, scatter the seed evenly, rake it in lightly and water if dry. Great for beds that would otherwise sit empty.
- 7–21 days after “Sow on Bare Ground” · Late July – early August
Check It Has Come Up
A green carpet should be showing. It smothers weeds and protects the soil from rain.
- 42–63 days after “Sow on Bare Ground” · Late August – mid September
Cut Down and Dig In
Before it flowers or sets seed (or when you need the bed), chop it down, let it wilt for a few days, then dig it into the top 20 cm.
- 14–28 days after “Cut Down and Dig In” · Early September – late September
Wait, Then Plant
Leave the bed for 2–4 weeks while it rots down before sowing or planting the next crop.
