Watermelons are grown in the southern regions of the U.S. because of the long growing season and warm temperatures. Surprisingly, the southwestern state of Arizona is a major watermelon-producing state. Watermelon varieties commonly planted in the desert of the southwestern U.S. include 'Charleston Gray,' 'Crimson Sweet,' and 'Sugar Baby.' Both long-vine and shorter bush-types are now available. Watermelons are ripe when the bottom part of the melon that contacts the ground is yellow and the tendrils nearest the fruit are brown. Watermelons have deep extensive root systems and grow best in sandy soil.
Things You'll Need
Soil test results
Recommended soil amendments
Find a place to plant watermelon seed that receives at least six hours of direct sun each day. Long-vine watermelon plants are spaced 10 feet apart and short-vine bush-types are spaced 4 feet apart.
Take a soil test to find out the correct soil amendments to add to the soil for best watermelon production. Contact your local county agricultural extension office for soil testing information. It is important to know your soil fertility and provide amendments at the right level. Although sandy soil in the southwestern U.S. desert is notoriously poor, adding too much fertilizer is expensive and can damage soil so nothing can grow. The extension office will also have watermelon variety recommendations and recommended planting dates.
Clear the planting area of any weeds and debris and prepare the planting bed. Spread a 3-inch layer of well-rotted compost over the bed along with the recommended soil amendments.
Work the amendments and compost into the soil of the designated planting bed. The amendments should be 6 inches deep in the soil to accommodate the extensive root system of the watermelon plants. Smooth the planting area with a rake.
Prepare to plant the watermelon seeds after all danger of frost has passed. Watermelons are not frost-tolerant. Designate a circle in the planting bed 3 feet in diameter for each watermelon plant and 10 feet apart. Make a mound 6 inches high around each planting circle so the circle will hold water.
Plant five or six seeds 1 inch deep, evenly spaced within the circle. Water the area deeply inside the planting circle where the seeds are planted. Keep the area damp until the seeds sprout in about one week.
Thin the watermelon plants to the strongest plant after they are actively growing in about three weeks. Add a 2-inch layer of mulch within the planting circle and around the remaining watermelon plant to conserve moisture.
Water the watermelon plants by soaking the soil around each plant once a week. Continue watering on the weekly schedule, unless there is rain, until the watermelons are ready for harvest in about 120 days.