Traditionally grown in Southern climates in sandy soil and summer heat, long-season watermelon might require 100 days or more to reach maturity. New cultivars of watermelon designed for short seasons mature in just 75 to 80 days, making it possible to grow them in the Northern gardens of Maine. If you have been avoiding growing watermelon because you thought your growing season was too short, it’s time to explore the proper varieties for your area and develop the techniques required to grow juicy, sweet watermelon in your backyard.
Choose a short season variety of watermelon like "sugar baby" or "golden crown." These mature in 70 to 75 days, making it possible to grow in nearly any garden in Maine. Fruit is small (6 to 10 pounds), but flavor matches that of other larger varieties.
Select a growing site that faces the southern exposure and receives full sun all day. Although watermelon grows with 6 to 8 hours of direct sunlight, full sun is preferred.
Till the area to a depth of 8 to 10 inches and remove any rocks, roots or other debris. Spread a 3- to 4-inch layer of compost or well-rotted manure over the soil and work it in well with a tiller or hand tools. Watermelon requires loose soil to grow.
Apply 10-10-10 fertilizer following the application rate on the container. Work it into the top 2 to 3 inches of soil with a hoe and rake the area smooth.
Spread black plastic over the watermelon patch and secure the edges with rocks or fresh soil. Cut large X's through the plastic spaced 2 to 3 feet apart along the rows. Space rows 6 to 10 feet apart.
Punch holes in the plastic with a sharp object or small stick to allow water to penetrate the plastic. Space holes 6 to 12 inches apart and adjust as necessary after rain.
Plant seedlings in the garden once the soil temperature reaches 65 degrees Fahrenheit and all danger of frost has passed in your area. Loosen the soil beneath the cut X's and position the seedling in the soil. Fill in around the roots with soil. Firm soil down with your hands to secure the roots and remove air pockets.
Water deeply once a week to saturate the soil to the root level. Use a hose or sprinkler to apply water at the base of each plant.