Watermelon: Sowing, planting and harvest calendar

Sow watermelons in a warm place, using individual pots with drainage holes and seed compost. Start them a few weeks before planting out, according to the variety and your climate, rather than on the same date everywhere. Follow the packet for sowing depth and germination temperature.

Keep the compost moist without waterlogging it. After germination, give the young plants plenty of light and protect them from cold. Avoid leaving them cramped in their pots for too long.

Gradually harden off the plants before transplanting. Wait until frost has passed and the soil has warmed; an unheated greenhouse may still be too cold at night. Handle the root balls carefully to avoid damaging the roots and plant in fertile, well-drained soil.

Check the actual temperature beside the pots, especially at night: a sunny window can become cold after sunset. Label every sowing with its variety and date. Choose a container that lets you remove the whole root ball at planting time, as repeated handling can damage roots. If the surface dries, water gently and allow thorough drainage rather than leaving the pot standing in water.

Watermelons can be sown directly once all risk of frost has passed and the soil has warmed well, provided the warm season is long enough. In cool climates, favour plants started in warmth and an early variety; growing under cover may help.

Choose a sunny position with fertile, well-drained soil. Follow the packet for sowing depth and spacing between plants and rows, which vary with the variety's vigour. Keep the soil moist during germination without waterlogging it.

Watch for slugs and snails that can damage young plants. Do not rely on eggshells as effective protection. After germination, thin if needed and water at the base; mulch can reduce evaporation and weeds.

Do not judge soil warmth by one sunny afternoon: consider night-time conditions and the forecast as well. Reserve room for the future vines before choosing sowing positions. Mark those positions so you do not step on them during emergence. If you retain one seedling from a group, avoid pulling up the shared soil and disturbing the roots of the plant you are keeping.

Plant young watermelons once all risk of frost has passed and the soil has warmed well. Gradually harden off plants raised under cover. Choose a sunny spot with fertile, well-drained soil; in cool climates, a greenhouse or polytunnel may be preferable.

Water the root balls before planting and handle them without damaging the roots. Allow enough room for the trailing stems: follow the recommended distances between plants and rows for the variety. Water after planting, then maintain consistent moisture without waterlogging the soil. Mulch can reduce evaporation and weeds. Adjust nutrient inputs to your soil rather than expecting a harvest without any feeding.

Prepare the holes before removing plants from their pots to limit root exposure. Support the root ball from underneath and keep the previous growing depth. Do not firm the soil by pressing on the fragile stem. Leave a path that will remain clear as the vines spread, so you can water and inspect developing fruits without treading on the crop. If you use temporary protection, ventilate it in sunny weather to prevent overheating.

Watermelon is grown as an annual: there is no rejuvenation pruning of the previous year's shoots. Do not routinely remove side shoots or healthy leaves. If the plant takes up too much space, gently guide young stems rather than removing every stem without fruit.

Limited pruning may help remove dead or diseased parts or contain an awkward stem. Use a clean tool and avoid cutting when the foliage is wet. Limiting fruit numbers depends on the variety, plant vigour and available season; it does not by itself guarantee large fruit. Preserve the leaves that feed the fruit and avoid severe pruning.

Harvest watermelons when ripe, according to the variety and growing conditions rather than a fixed date. Look for several signs: the patch touching the ground usually turns cream or yellow, and the tendril near the fruit may dry out. This last sign varies with the variety; a hollow sound alone is not enough either. Watermelons do not continue to ripen after harvest.

Cut the fruit stalk with a clean, sharp tool, leaving a small piece attached to the fruit. Do not pull on the stem and avoid knocks that damage the rind. Keep whole fruits in a cool place and use them soon; storage life depends on their condition and how they are stored. Once cut, cover the flesh and refrigerate it.

Compare fruits of the same variety rather than watermelons of different types. The number of days on the packet is a guide, but does not replace observation in the garden. To inspect the underside, support the fruit without rolling it or twisting its stalk. When moving it, carry it from underneath with both hands: the piece of stalk left after cutting is not a handle.