Gardeners with ample growing room often enjoy growing at least a small watermelon patch to provide a home-grown treat for the months of summer. Choose a watermelon variety suited for your growing area because some kinds of watermelon take longer to be ready to harvest. For best results, start the watermelon seeds indoors in peat starter pots several weeks before the garden soil is ready.
Fill the starter pots with potting soil and place two seeds in each pot. Cover the seeds lightly with soil and water the soil with a spray bottle. Keep the soil evenly moist during germination.
Keep the starter pots in a warm location with a constant temperature between 26.5 and 29.5 degrees Celsius (80 and 85 Fahrenheit). Spray the soil often to keep it moist. When the seedlings are over 7 cm (around 3 inches) tall, thin the seedlings by removing the weakest plant so that one seedling remains in each pot.
Prepare the growing area outside when the soil is warm. Make sure there is no danger of frost. Watermelons thrive in well-draining soil, so add compost to a clay soil if necessary. Add starter fertiliser to the soil before planting the seedlings. Consult the fertiliser package for the recommended amount of fertiliser for the size of your growing area.
Dig holes between 60 and 90 cm (2 and 3 feet) apart that are large enough for the starter pots. Place each starter pot in the prepared holes and replace the soil carefully around the seedlings. Water generously.
Control weeds around the watermelon vines by hoeing carefully to loosen the weeds. Do not water the watermelon plants unless drought conditions exist.
Harvest watermelons when the tendrils on the stems become brown. The surface should be hard and rough. Look for a dull outer surface on the melons. The area of the watermelon that is in contact with the soil may turn slightly yellow.
If you are planting a variety of seedless watermelon, also plant a regular seeded variety of watermelon. Seedless watermelons will not produce fruit without a seeded variety planted nearby for pollination.
Do not start watermelon seeds indoors more than three weeks prior to planting outside because larger watermelon seedlings do not tolerate transplanting well.