Watermelons are surprisingly easy to grow as long as the plants have plenty of room to spread, good drainage, lots of sunlight, and a sufficiently long growing season. Gardeners in northern climates should choose early ripening varieties. Popular watermelon varieties include Sugar Baby, Sweet Favorite and Cotton Candy.
If you live in a colder climate, consider starting seeds indoors or purchasing seedlings to transplant into the garden.
Work plenty of compost or organic slow-release fertilizer into the top few inches of soil in your watermelon patch. Mound the soil into small hills spaced 8' to 10' apart, less for compact varieties, and cover the hills with black plastic to increase soil temperature, maintain moisture, control weeds and speed growth.
Watermelons need a location that receives 8 to 10 hours of sunlight per day. Work plenty of compost or organic slow-release fertilizer into the top few inches of soil. Mound the soil into small hills spaced 8' to 10' apart, less for compact varieties. Cover the hills with black plastic to increase soil temperature, maintain moisture, control weeds and speed growth. Tack down the corners with yard staples.
Wait until soil temperatures reach 70 degrees Fahrenheit before planting seeds to ensure germination. Make a slit in the black plastic and press four watermelon seeds 1" deep into each hill. Cover the seeds with soil and water them. When seedlings sprout, thin to just two plants per hill.
Watermelons are heavy drinkers and feeders. The plants require about 1" of water per week and regular applications of fertilizer. If not using black plastic, add a thick layer of mulch around plants to conserve moisture and keep down weeds. To protect the young plants from cucumber beetles, many gardeners cover them with floating row covers. These covers must be removed when flowers appear to allow pollination.
Watermelons typically require 80 to 100 days to reach maturity. Signs that the fruit is ready for harvest include stopping of growth, yellowing underside, and shriveling of the stem at the base of the fruit. To harvest the melon, snip the stem from the vine with shears.