Watermelon is loaded in vitamin C, making it a healthy fruit to eat. This fruit is hardy in the USDA zones 3 through 11. There are over 50 varieties of heirloom watermelons. My dad always liked to grow and buy Black Diamond and Charleston Gray. Now it is so hard to find those varieties in the local grocery stores. When growing heirloom watermelons, you can save the seeds from season to season. The plants will always be the same as the parent plant. If you live in the northern part of the united states, an early variety may be the best choice for you. It takes 75 to 75 days for early season varieties. The ripe fruit can weigh 6 to 10 pounds. Main season varieties take 80 to 85 days before the fruit can be harvested. These can weigh 20 to 26 pounds.
Prepare the Soil
Watermelon needs a sunny location in which to grow. Till the soil to make it light and well draining. Remove rocks, sticks and hard dirt clods. Amend the soil with 3 to 4 inches of well-rotted compost along with 2 inches of sand. If your soil is already sandy, omit adding more sand. Level the ground with the back of your rake.
Form the Growing Mounds
Watermelons grow in mounds that are 2 to 3 feet square. To form mounds, pull the soil up with a hoe or shovel until the soil is mounded 1 foot high. Leave 2 to 6 feet between each mound. The purpose of growing the watermelon in mounds is so the roots to grow deep in the soil. It draws away excess moisture, but it conserves moisture during dry conditions. Figuring on one plant per mound, form as many mounds as you want or need.
Plant the Seeds
Sow the watermelon seeds when the temperature remains above 60 degrees Fahrenheit. Place two to three seeds in the middle of each mound, spacing them equally apart. Push the seeds into the soil with your finger so they are 1 inch deep. Cover the seeds and firm the soil lightly with your fingers.
Watering and Fertilizing Through the Season
For watermelon seeds to germinate to develop and grow, they need water. Do not allow the soil to dry out, but don’t water it so much that the soil is soggy. In 7 to 10 days, the seeds will germinate. When the seedlings reach 4 inches in length, it is time to thin out a plant. Cut the weaker plant off at the ground level. You can pull the plants out, but do so very carefully so you don’t hurt the roots of the plant you are leaving. There should only be one plant per mound.
When the watermelon vines begin blooming, you will need to give them 1 to 2 inches of water per week. One week after the watermelon’s flower, give them some fertilizer of 6-10-10. Three weeks later, give them another dose of fertilizer. Mix and apply the fertilizer according to label directions.
Cut back on the watering when you see the fruit forming. Water enough to keep the soil moist, but not soggy. To help the soil to conserve moisture, lay down a 2 to 3-inch layer of mulch around the plants.
When the watermelon vines reach 6.5 feet, pinch off the tips of the vines. As you do this and throughout the season, check the plants for slugs. If you find any, pick them off. To help you control the slugs, set out several low saucers of beer on the ground. The slugs crawl into the beer, but they won’t come back out. Dump the beer and slugs into a garbage bag when they become half-full. Fill the saucers with fresh beer to catch some more.
“Growing Muskmelon and Watermelon: University of Nebraska Lincoln;” Ralph E. Neild; 1973
“Melons for the Passionate Grower”; Amy Goldman; 2002