Watermelons can be grown in all areas of the country and are a favorite summer treat. Large watermelons require a lot of space to grow and a long growing season. According to the University of Arkansas Cooperative Extension Service, watermelons typically grow to 18 to 25 pounds.
In some parts of the country, there is a short growing season and seeds may be started indoors about three weeks before transplanting outside. Place two or three seeds in each peat pot. Thin to the best one or two plants. Seeds or young plants may be planted after soil is warm—62 degrees Fahrenheit or higher—and all danger of frost is past.
Watermelon plants require a lot of space. Seeds may be planted in hills or in rows. Space watermelon plants 6 feet apart in hills. Thin to the best three plants per hill, advises the Arkansas extension service. If planting in rows, watermelon seeds or seedlings should be seven to 10 feet apart.
Avoid planting seeds too early. If the plants are too large they adjust poorly to being transplanted. If you have a limited amount of space, consider planting “bush” watermelons, which require less space and mature more quickly. According to the University of Illinois Extension, there are more than 100 varieties of watermelon.