UK sowing calendar
When to sow watermelon in the UK
🫙 Best under glass — greenhouse or polytunnel in most of the UK
Watermelon sowing calendar (UK)
| Sow under cover | mid-Apr-mid-May |
|---|---|
| Sow / plant outdoors | n/a (greenhouse only) |
| Harvest | late Jul-early autumn |
Needs more heat than cantaloupe and is really greenhouse/polytunnel-only in the UK - it will not reliably ripen outdoors. Sow under cover at 18-21C and choose a compact, cool-climate variety such as 'Little Darling'.
UK timing runs on the last-frost date, not a USDA zone. Most of Britain sees its last frost around mid-May, with the north and exposed inland gardens a week or two later and the mild south-west and coast earlier. Tender crops start under cover and only go out once frost has passed; hardy crops can be direct-sown as soon as the soil is workable.
Timing aligned with the RHS grow-your-own guide for watermelon.
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When to sow watermelon in the UK — FAQs
When should I sow watermelon in the UK?
Sow watermelon under cover mid-Apr-mid-May, then outdoors n/a (greenhouse only). Needs more heat than cantaloupe and is really greenhouse/polytunnel-only in the UK - it will not reliably ripen outdoors. Sow under cover at 18-21C and choose a compact, cool-climate variety such as 'Little Darling'.
Can you sow watermelon outdoors in the UK?
Watermelon is tender and largely greenhouse-only in the UK — outdoors it is marginal and only worth trying in the warmest, most sheltered spots. Needs more heat than cantaloupe and is really greenhouse/polytunnel-only in the UK - it will not reliably ripen outdoors. Sow under cover at 18-21C and choose a compact, cool-climate variety such as 'Little Darling'.
When is watermelon ready to harvest in the UK?
Watermelon is typically harvested late Jul-early autumn in the UK, depending on your sowing date, cultivar and region.
Is it too late to sow watermelon?
It depends on the month and your region. Watermelon has a UK outdoor window of n/a (greenhouse only); northern and exposed gardens run a week or two behind the south. Open Growli and tell it your postcode for timing tuned to your own last-frost date.