Growing watermelon (Citrullus lanatus) in your home garden has many advantages over buying watermelon from a grocery store. The best benefit to growing your own watermelon is that you harvest the fruit when it is at its peek. Commercially grown watermelon is harvested before the fruit reaches its maximum sweetness because the unripe fruit will not suffer as much shipping damage as ripened fruit. Watermelon that is picked before it is fully ripe will not continue to ripen. When you grow your own watermelon, you can check the fruit before harvesting to make certain it is at maximum sweetness.
Direct Seed Planting
Watermelon seeds can be bought from gardening stores and from most online seed suppliers. Seeds are sown directly into the ground in small mounds after the last frost. Seeds will germinate in soil that is 60 F or higher. Seedless watermelons need a soil temperature of 70 F or higher to germinate. Plant 2 to 4 seeds in each mound at a depth of 1 inch, spaced at 8 feet apart on all sides. After the seeds have germinated, thin the seedlings so there are two plants per mound.
Watermelon is a long season, warm weather crop and it can take 70 to 90 days to reach maturity. In areas with a short growing season, starting transplants indoors before the last frost can add four to five weeks to the area’s growing season. Plant one to two seeds per peat pot, at a depth of one inch, up to five weeks before the last frost. The soil temperature should be kept at 60 to 70 F for the seeds to germinate. Use supplemental lights hung 6 to 12 inches above the plants to provide the plants with 14 hours of light. If the seedlings do not get enough light, they will become leggy. The soil will need to be kept moist while the seeds are germinating with the use of misting. Seedlings can be planted outside after the last frost and the soil temperature is between 65 and 70 F. Before transplanting the plants, harden them off by setting the plants outdoors during the days for three to four days and bringing the plants indoors.
Site, Soil, Fertilizer
Watermelon is grown in the full sun and needs eight to ten hours of sunlight each day. The soil needs to be well drained and slightly acid with a pH between 6.0 and 7.0. Fertilize soil with 10-10-10 or 13-13-13 base fertilizer at 3 pounds per 100 square feet before seeds are planted. The soil should also be tilled to a depth of 6 inches. After the seeds have sprouted or the transplants have been planted, mulch with dried grass clippings to prevent weeds and to hold the moisture in the soil.
Watermelon needs a lot of water to grow because the fruit is made up almost entirely of water. Give the plants 1 to 2 inches of water a week. Drip irrigation works best for watermelons, but most home gardeners will water the plants from above. When watering the plants, avoid watering at night because this may cause foliage diseases. Water the plants in the early afternoon so that the sun can dry off the leaves before nightfall.
There are several different methods to test watermelons for maturity. The most surefire method is to cut a piece out of one of the watermelons in the garden. If it is dark pink inside, the fruit has reached maturity. Another method to examine the curly tendril at the stem. If it is dry, the watermelon is ready to be harvested. You can also check the color of the underside of the watermelon. If the underside is yellow, it is ready to harvest. Cut the fruit from the vine to prevent any damage to the fruit. The melons are washed and can be stored at temperatures of 52 to 60 F for 2 to 3 weeks.