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Sowing Calendar
Guide indicating when to start seeds indoors and when to direct sow or transplant outdoors. Months assume a temperate Northern Hemisphere climate (USDA zones 5-8); adjust by 2-4 weeks for warmer or colder regions.
Indoor vs outdoor sowing
- Indoors: start seeds in trays 4-8 weeks before the last frost date for your area
- Outdoors: direct sow or transplant after the last frost date when soil has warmed
- Last frost dates vary by region, consult your local gardening zone
- Sow in succession every 2-3 weeks for a continuous harvest
Key terms
- Indoor sowing: start under artificial light or in a bright windowsill in trays or modules; requires later transplanting
- Direct sow: sow seeds directly into the ground or a raised bed where they will grow
- Transplant: move seedlings started indoors to their final outdoor growing position
- Hardening off: gradually acclimate indoor seedlings to outdoor conditions over 7-10 days before transplanting
General tips
- Label every tray or pot immediately after sowing, memory is unreliable after a few weeks
- Use fresh seed compost, not garden soil, for starting seeds
- Most seeds germinate best at 18-24°C (65-75°F)
- Keep soil moist but not waterlogged during germination
UK last frost dates and gardening zones
Unlike the US USDA zone system, the UK uses RHS hardiness ratings (H1a to H7). Last frost dates vary significantly across the country:
| UK region | Average last frost | Notes |
|---|---|---|
| London and SE England | Mid-March to early April | Warmest region; can start outdoor sowing earlier |
| South West England, W Wales | Late March to April | Mild, wet, Atlantic influence; good for early brassicas |
| Midlands, East Anglia | April to early May | More continental; cold nights possible into May |
| North England, Yorkshire | Late April to mid-May | Allow 2-3 weeks later than SE England |
| Scotland (lowlands) | Late April to May | Shorter season; focus on quick-maturing varieties |
| Scottish Highlands, N Ireland uplands | May to early June | Short season; polytunnel strongly recommended |
Two key UK gardening dates
- Chelsea Chop (late May, around the RHS Chelsea Flower Show): the traditional signal to cut back herbaceous perennials and plant out tender half-hardies like dahlias, zucchini, and basil outdoors. Corresponds roughly with reliable frost-free conditions in most of England.
- Potato Day (second Sunday in February): the traditional start of the UK potato-chitting season. Seed potatoes are laid out in egg boxes to chit (sprout) in a light, cool, frost-free place before planting out in late March-April.