Watermelon is a warm-weather vegetable grown in all parts of the United States. There are several watermelon varieties, including seedless and dwarf. Vines from watermelon continue working in the garden after harvest, incorporating themselves into the soil as organic matter. Watermelon requires a long growing season with high temperatures.
Watermelons should be planted as soon as the soil is warm and the regular air temperature is between 70 and 80 degrees Fahrenheit. Soil temperature at the 4-inch level should be between 60 and 65 degrees, says Clemson University Extension. You can give plants an early start by germinating seeds indoors and transplanting seedlings as soon as the soil is warm enough to plant.
Spacing and Depth
Watermelon vines require a lot of spacing to grow properly. Seeds require planting at a 1-inch depth in hills that are spaced 6 feet apart. Rows require 7 to 10 feet of space to allow for vine growth, says the University of Illinois Extension. Transplants require planting 2 to 3 feet apart, with spacing between rows 4 to 5 feet apart.
Watermelons require a large amount of water since 92 percent of the watermelon fruit is comprised of water. Watering in the morning is required for overhead irrigation systems to prevent burning of the flowers, which produce fruit and are pollinated by bees. Watering to a depth of 6 inches is required. Plastic or wood mulch is spread thinly across a watermelon patch to retain water and prevent the soil from drying out during the summer heat.
Conduct a soil test of the watermelon patch to determine the correct amount of fertilization. Under-fertilizing the plant will reduce the size and production of the plants. Generally, 1 lb. of nitrogen, 2 lbs. of phosphorus, and 3 lbs. of potash are required per 1,000 square feet of the garden. Watermelon will grow well in a soil pH 5.0 to 6.8, so lime application is rarely required, says Ohio State University.
Watermelon harvest depends on the specific variety and how long it takes to grow to maturity. To test the watermelon for ripeness without knowing the harvest time required, tapping the watermelon with a finger and listening for a muffled, dull thump tells you the fruit is ready. Leaves around the fruit will turn brown and curl.