When to plant watermelons?
On the RHS melon page, grow watermelon in a greenhouse or a polytunnel, with a variety for cooler climates or a compact one, and that page prints no separate sowing month for it. In Sicily the open field runs from mid-March to mid-June, the semi-forced crop in February-March and the large tunnels in late January, while Campania and Umbria write no month.
When, by region
| North | Centre | South | |
|---|---|---|---|
| Sowing | The RHS grows it in a greenhouse or a polytunnel, with a variety suited to cooler climates, or a compact one such as 'Little Darling'. A sowing month for watermelon, on that page, is not printed. The months from mid-April to mid-May, and the 18-21 °C (64-70 °F), are written for melon, not for watermelon. | Umbria 2025 has watermelon and does not write a month. Return after at least 2 years, and the crops before and after are not cucurbits. | Campania sets no month. Growth is happy at 25-30 °C (77-86 °F) by day and 15-20 °C (59-68 °F) at night. You can sow in the field or transplant. In Sicily the open field runs from mid-March to mid-June. The semi-forced crop, under small tunnels, is February-March, with harvest by June. Under the large tunnels, late January, with harvest by May. |
| Spacing | A watermelon spacing, on the RHS page, is not written. The 45 cm (18 in), the 90 cm (3 ft) and the 40 cm (16 in) pot belong to melon, on the same page. | Umbria does not write a spacing. | In Campania the table prints 0.2-0.3 plants per square metre above 10 kg, 0.35 for fruit of 7 to 10 kg, and 0.5 on the row that prints a weight below 10 kg. With grafted plants, about 20 per cent less. In Sicily, open field, 2.5-3 m between rows and 1.0-1.5 m along the row, 2,700-3,300 plants per hectare. |
Among the cucurbits, in Campania, it is the one that wants the most heat. Frost stops it.
A greenhouse or polytunnel, a variety for cooler climates and the compact 'Little Darling' are from the RHS melon page, which prints no watermelon month. 25-30 °C (77-86 °F) by day, 15-20 °C (59-68 °F) at night, 0.2-0.3, 0.35, 0.5 plants per square metre and 20 per cent less on grafted plants are from Campania, which names no month. Mid-March to mid-June, February-March, late January, 2.5-3 m, 1.0-1.5 m, 2,700-3,300 plants, 1.50 by 3.00 m and 1.80-2.00 by 4.00-5.00 m are from Sicily. At least 2 years, and the ban on other cucurbits, are from Umbria 2025, which writes no month. Melon, on the same RHS page, is in when to plant melons. The months are in the January calendar, February, March, April, May and June.
No month on the RHS page
The RHS melon page says watermelon can be grown, and that the safer route is a greenhouse or a polytunnel, with a variety for cooler climates or a compact one such as 'Little Darling'. A month-by-month chart for watermelon, on that page, is not there. Sowing from mid-April to mid-May, at 18-21 °C (64-70 °F), is written for melon seed. Those months do not move across to watermelon.
Melon, with its months, is in when to plant melons. Cucumber, same family, is in when to plant cucumbers.
Sicily, three windows
In Sicily planting is mostly with plants raised in modules. In the open field, from mid-March to mid-June. Between rows 2.5-3 m, along the row 1.0-1.5 m, 2,700-3,300 plants per hectare. Under small tunnels, 70-80 cm high and 80-90 cm wide, the transplant is in February-March, to harvest by June, generally at 1.50 by 3.00 m. Under the large tunnels, 4 m wide, the transplant moves forward to late January, to harvest by May. The spacing under tunnels is generally 1.80-2.00 m by 4.00-5.00 m. Pollination under cover is done with bees. The natural open-field cycle is spring and summer.
In Campania no month is written. You can sow in the field or transplant, including on a mulch. Growth is happy at 25-30 °C (77-86 °F) by day and 15-20 °C (59-68 °F) at night. The density table prints three rows: above 10 kg, 0.2-0.3 plants per square metre; from 7 to 10 kg, 0.35; and a row that prints a weight below 10 kg, at 0.5. With grafted plants the density drops by about 20 per cent on average. Seedless varieties are always transplanted, with a pollinator: one row in three, or one plant in every 3-4 along the row. A second pollinator transplant, 2-3 weeks later, covers the late flowers. Umbria, in 2025, has the sheet and does not write the month. Return after at least 2 years, and the other crops are not cucurbits. One repeat in five years, if the variety resists Fusarium or the plant is grafted. In 5 years you may also follow watermelon with melon, or the reverse, with varieties that resist fusarium wilt, grafted or not.
Where not to return at once
In Sicily, so the soil does not tire, at least two years without watermelon, and in between no solanums and no other cucurbits. Grafted plants are the route the guide gives for that problem. In Campania, outside the specialist farms, the succession is five years, with at least three crops and at most one repeat. Two cycles in the same year count as one year. The home plan is in crop rotation. Water, on the soil and not on the leaves, is in watering.
In the app
Every plant in the catalogue has its own sowing calendar, and weather alerts for your area help you judge whether to sow now or hold off.
Frequently asked questions
What month does the RHS write?
None, for watermelon. It writes a greenhouse or a polytunnel, a variety for cooler climates, or a compact one such as 'Little Darling'. From mid-April to mid-May, at 18-21 °C, is the melon sowing, on the same page.
What date does Sicily write?
Open field from mid-March to mid-June. Semi-forced crop in February-March, harvest by June. Large tunnels in late January, harvest by May. Between rows, in the open field, 2.5-3 m, and 1.0-1.5 m along the row.
What about Campania and Umbria?
No month. Campania writes 25-30 °C by day and 15-20 °C at night, direct sowing or a transplant. Umbria 2025 sets no month: return after at least 2 years, with no other cucurbits.
What does the density table print?
Three rows: above 10 kg, 0.2-0.3 plants per square metre; from 7 to 10 kg, 0.35; and a row that prints a weight below 10 kg, at 0.5. With grafted plants, about 20 per cent less. In Sicily, 2,700-3,300 plants per hectare in the open field.
How are seedless watermelons planted?
In Campania they are always transplanted. They need a pollinator cultivar: one row in three, or one plant in every 3-4 along the row. A second pollinator transplant, 2-3 weeks later, covers the flowers that open late. The hives sit in the middle or around the field, 3-4 per hectare.