When to sow phacelia green manure
In zone 8, most of the UK: sow direct from August to October and from March to April. Flowers about 60 days later.
Growing stages
Phacelia green manure: calendar by hardiness zone
| Zone | January | February | March | April | May | June | July | August | September | October | November | December |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Zone 6 | Flowering | Sowing or planting | Flowering | Flowering | Sowing or planting | Sowing or planting | ||||||
| Zone 7 | Flowering | Sowing or planting | Sowing or planting, Flowering | Flowering | Flowering | Sowing or planting | Sowing or planting | |||||
| Zone 8reference | Flowering | Sowing or planting | Sowing or planting, Flowering | Flowering | Flowering | Sowing or planting | Sowing or planting | Sowing or planting | ||||
| Zone 9 | Flowering | Sowing or planting, Flowering | Sowing or planting, Flowering | Flowering | Flowering | Sowing or planting | Sowing or planting | |||||
| Zone 10 | Flowering | Sowing or planting, Flowering | Flowering | Flowering | Sowing or planting | Sowing or planting |
- Zone 6
- −23 to −18 °C (−10 to 0 °F): high mountains
- Zone 7
- −18 to −12 °C (0 to 10 °F): upland Britain, eastern France, the Alps
- Zone 8
- −12 to −7 °C (10 to 20 °F): most of the UK and France
- Zone 9
- −7 to −1 °C (20 to 30 °F): south-west England, Brittany, Atlantic and Mediterranean coasts
- Zone 10
- −1 to 4 °C (30 to 40 °F): Isles of Scilly, the French Riviera, coastal Corsica
Indicative months. A cold year or a garden at altitude shifts everything by a month; watch the frosts too.
Phacelia green manure in practice
- Spacing
- 5 cm along the row, 10 cm between rows
- Sun
- copes with part shade
- Watering
- low
- Difficulty
- easy
- In a pot
- yes
- Support
- none
- Family
- Borage family (Boraginaceae)
Questions about phacelia green manure
When to sow phacelia green manure?
In zone 8: sow direct from August to October and from March to April. The four other zones are in the calendar above; at altitude or after a long winter, aim for the end of the window.
How long until it flowers?
About 60 days after sowing in zone 8, then it flowers for about 1 day.
How far apart?
5 cm between plants along the row and 10 cm between rows.
Updated 20 October 2026, Hortipix catalogue version 1. Windows still being checked against Le Guide Clause, Vilmorin and Terre vivante (RHS and Cornell for the UK and the US), compared with OpenFarm (CC0). They remain indicative.