Sow squash indoors from mid-April to early May in the UK and plant out once the last frost has passed in late May or early June. Summer squash crop from July; winter squash need the full season and are harvested September–October before the first frosts.
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Sowing dates and growing advice verified against RHS guidance by the SoilCommander Growing Team.
Squash Planting Calendar
| Task | Timing | Notes |
|---|---|---|
| Sow indoors | April – May | 18–20°C; sow on edge in individual pots |
| Transplant outdoors | Late May – June | After last frost; harden off for 1–2 weeks first |
| Harvest (summer squash) | July – October | Pick regularly at 10–20cm |
| Harvest (winter squash) | September – October | Cure in a warm, dry place for 10 days before storing |
Regional Planting Notes
The RHS notes indoor sowing is “particularly beneficial in colder regions, where outdoor sowing would have to be quite late” — in line with the Met Office’s finding that the last frost further north and on higher ground can linger “well into May and, in a few places, even into June.” In Scotland and northern England, start seed indoors in April rather than waiting to sow or plant outdoors, to make the most of a shorter growing season.
UK Variety Picks
- Crown Prince — RHS AGM, excellent storage, blue-grey skin, superb flavour
- Butternut Waltham — classic butternut, suits UK if given a warm summer
- Uchiki Kuri — small red onion squash, reliable in the UK, sweet flesh
- Defender — summer courgette/squash type, very prolific, pick young
Common Mistakes to Avoid
- Watering inconsistently. Insufficient water can encourage powdery mildew — keep watering consistent, especially as fruit develops.
- Cutting fruit too close to the stem for storage. The RHS advises leaving at least 10cm of stem attached; cutting closer leaves a soft area vulnerable to rot in storage.
- Overcrowding plants. Overcrowded conditions encourage fungal disease — trailing types need around 1.5m spacing.
Frequently Asked Questions
Why does my squash have powdery mildew?
Insufficient watering is a contributing cause — water consistently, especially once fruit is developing.
How do I harvest squash for storage?
Cut fruit with at least 10cm of stem still attached; cutting too close to the fruit leaves a soft area that's vulnerable to rotting in storage.
How much space do squash plants need?
Trailing varieties need around 1.5m spacing to avoid the overcrowding that encourages fungal disease.
Plan Your Squash Sowings
Trailing varieties need real spacing to avoid powdery mildew — get sowing dates and spacing guidance for squash and 38 other UK crops.
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Last updated 4 July 2026
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