Choose a location where your plants will get full sun and good air circulation. A gentle, south-facing slope is ideal. Watermelons can grow in many kinds of soil, but prefer a light, sandy, fertile loam that is well-drained. Add generous amounts of manure, compost and leaves to your garden and work the soil well prior to planting. Watermelons like lots of water. Keep the soil moist at all times.
How to Plant:
Soak seeds in compost tea for 15 minutes prior to planting. Plant in hills 1/2-1 inch deep. For regular watermelons varieties, sow two to three seeds per hill, spacing the hills 8-10 feet apart. Thin seedlings in the hill to two seedlings one week after they have germinated. Small bush varieties may be spaced 3 feet apart.
Transplants: If black plastic was used to pre-warm the bed, cut holes in the plastic and set the plants 1/2-1 inch deeper than they were growing in their containers. Water thoroughly after transplanting.
Watermelons are heavy feeders. Apply a slow release balanced fertilizer during planting. Spray plants with liquid fertilizer and seaweed throughout the growing season. Cut back on nitrogen levels after flowers form. Continue with phosphorous and potassium applications until just before harvest.
Tip: Cover plants with floating row cover to keep the air and soil warm.
Determining when to harvest watermelons can be difficult and requires some experience. For the most part when ripe, the curled tendril at the stem end dries to brown, the underside of the melon turns yellow or cream colored, and the melon will yield a deep, resonant sound when thumped. Allow 80-90 days for bush varieties to reach maturity and 90-100 days or more for the larger varieties.
Insects and Diseases:
Cucumber beetles, aphids, mites, squash bugs, fusarium wilt, anthracnose, alternaria leaf spot, and curly top are some of the problems home gardeners may encounter while growing watermelon.
Seed Saving Instructions:
Watermelons will cross-pollinate, so isolate 1/2 mile from other varieties to maintain purity. When fruit is ready to eat, the seeds are also mature. Collect seeds and wash gently with a mild dishwashing soap. Rinse thoroughly and allow to dry.