Vegetable · Cucurbitaceae
When to plant marrows
Marrows are harvested larger than courgettes, but simply leaving every fruit to grow can reduce the number of later fruit. Decide how many large marrows you can use and select the cultivar for that purpose.
Start seed indoors
3 weeks before
Counted from your last spring frost.
Plant out
2 weeks after
Counted from your last spring frost.
Sow direct
2 weeks after
Counted from your last spring frost.
Choose a place for estimated dates and local climate checks.
Timing, in frost-relative terms
These offsets are the starting assumptions used by our calendar for marrows. They do not establish suitability in every climate. Your seed packet, cultivar and local growing advice take priority; in frost-free places the calendar uses monthly temperature patterns instead.
- Start seed indoors 3 weeks before the last frost.
- Plant out 2 weeks after the last frost.
- Sow direct 2 weeks after the last frost.
- Expect 60–80 days to maturity, counted from sowing.
Getting the timing right
Give plants a sunny warm position with enough leaf space and a drained root zone. Keep moisture reasonably steady while fruit swells, and inspect under foliage so oversized or damaged fruit does not go unnoticed.
Frost tolerance
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.
Classified as tender, with a catalog cold-damage reference of 0°C (32°F)32°F (0°C). Exposure duration, growth stage and acclimatisation change cold tolerance.
Before you plant marrows
Use the calendar to plan ahead, then check the conditions in your own garden.
- Measure the soil at sowing depth. Aim for at least 15°C (59°F); the calendar estimates soil warmth from air temperatures and cannot measure your bed.
- Check the local overnight forecast before planting out. Delay planting or keep protection ready if frost is forecast, even after the historical last-frost date.
- Harden off plants raised indoors: gradually expose them to outdoor light, wind and temperature before their final move into the bed.
- Use the maturity range on your seed packet when choosing a variety. Cold, short days and transplant stress can make harvest later than the calendar estimate.
Choose deliberately between young squash and larger marrow
Give plants a sunny warm position with enough leaf space and a drained root zone. Keep moisture reasonably steady while fruit swells, and inspect under foliage so oversized or damaged fruit does not go unnoticed.
Cut selected marrows at a useful kitchen size with a short intact stalk. If storage is intended, follow the variety's maturity and keeping guidance rather than assuming every enlarged courgette will store well. Do not eat squash that tastes unusually bitter.
What to record this season
What size was useful in the kitchen, and did leaving large fruit reduce later production? Add the cultivar, sowing date and conditions to your growing record so you can compare next season.
Further reading: RHS squash growing guide . General crop guidance; local dates on this site are calculated separately. Source checked 19 September 2026 by Safe to Plant; this is not an expert review.
The RHS reference is written for UK growing conditions. Use its cultivation advice with local seasonal guidance; UK sowing months are not worldwide planting dates.
How the dates are calculated and their limits · Keep a growing record · Report a local discrepancy