Why Timing Matters
Sowing at the right time is one of the most important factors in gardening success. Two main variables determine your sowing window:
- Last frost date – the average date of the last frost in spring in your region
- First frost date – the average date of the first frost in autumn
Most sowing guidelines are expressed relative to these dates: "sow outdoors after last frost," or "start indoors 6 weeks before last frost date." Know your local frost dates before planning.
Key Terms
Direct sow / sow outdoors: Plant seeds directly in the garden bed. Start indoors / under cover: Start seeds in pots inside (or in a heated greenhouse) several weeks before outdoor conditions allow, then transplant outside. Transplant: Move seedlings from indoor pots to the garden. Succession sowing: Sow small batches every 2–3 weeks for continuous harvest rather than all at once. Hardy: Can survive frost. Half-hardy: Can tolerate light frost briefly. Tender: Will die if touched by frost.
Sowing Calendar (Northern Hemisphere, Temperate Climate)
The timing below assumes a last spring frost around late April (UK/Northern France/similar climates). Adjust earlier or later based on your region.
January–February (Under Cover Only)
- Onions from seed – long growing season; start early under heat
- Celery – needs warmth and a long start
- Chillies and sweet peppers – very long season; start as early as possible
- Broad beans – can be sown in pots in January for early crops
March (Under Cover; Some Hardier Crops Outdoors Late Month)
- Tomatoes – start indoors on a sunny windowsill or heated greenhouse; transplant after last frost
- Aubergines / eggplant – similar to tomatoes
- Leeks – start in trays indoors; very slow to develop
- Courgettes (zucchini) – start a pot indoors late March for May transplant
- Hardy salad leaves – can be sown under cloches or cold frame outdoors
- Peas – direct sow in mild areas from late March; tolerate light frost
April
- Lettuce and salad leaves – direct sow outdoors when soil reaches 10°C; succession sow every 3 weeks
- Spinach – direct sow; bolts in heat, so spring sowing is better than summer
- Beetroot – direct sow outdoors from mid-April
- Carrots – direct sow from mid-April in warm soil; resents transplanting
- Radishes – fastest crop; direct sow, harvest in 4–6 weeks
- Spring onions/scallions – direct sow
- Herbs: chives, coriander, dill – direct sow outdoors
May (After Last Frost)
- French beans (bush/climbing) – direct sow after last frost; killed by any frost
- Runner beans – direct sow after last frost
- Courgettes – transplant earlier-started plants or direct sow
- Cucumbers – direct sow or transplant; need warmth
- Sweetcorn – direct sow in blocks (for wind pollination) after last frost
- Basil – transplant after last frost; very frost-sensitive
- Winter squash and pumpkins – direct sow or transplant; need a long season
June–July
- Autumn brassicas – sow broccoli, kale, Brussels sprouts now for autumn/winter harvest
- French beans – last successional sow for late-season crop
- Salad leaves – succession sow continues
Late Summer (August–September)
- Hardy winter salads – spinach, corn salad, winter lettuce
- Garlic – plant cloves in October for summer harvest
- Spring bulbs – planted in autumn for spring flowers (not a vegetable, but the timing matters)
Tools for Planning
The Sowing Calendar on this site lets you input your climate zone or last frost date and view customized sowing windows for common vegetables and herbs.
General Rules
- Soil temperature matters more than air temperature – most seeds need at least 10–12°C soil to germinate reliably
- Never sow frost-tender plants until after your last frost date has passed
- Succession sow salad crops every 2–3 weeks to avoid feast-and-famine harvests
- Labels and dates are not optional – you will not remember what you planted where