How to Plant, Grow, and Save Seeds from Watermelon (Citrullus lanatus)
Although watermelon requires a long growing season, if you start this sprawling plant early enough in the year, you can enjoy its fruits from late summer to early fall. Watermelon, like other vining plants, need plenty of space to grow.
Watermelon can be direct-sown outside after danger of frost has passed. Plant watermelon into 12” tall hills of soil that are spaced at least 6 feet apart. Sow 6-8 seeds per hill, later thinning to 3-4 plants per hill. Sow watermelon seeds ½” deep. Water seeds into the hills after planting. While it is simple to direct-sow watermelon seeds, you can also start watermelon seedlings indoors four to six weeks before the last frost date.
Watermelon plants can suffer from anthracnose, cucumber wilt, downy mildew, and powdery mildew. Row cover can be used to keep pests off plants early in the season.
When harvesting watermelon, take care to cut the stem with a sharp knife or garden tool rather than pulling the plant from the vine. Maturity indicators differ among varieties but include the ground spot turning yellow, the tendril opposite the fruit shrivelling, or the rind taking on a dull and waxy appearance.
Eating and Storing
Watermelon is most often enjoyed fresh and cold as a summertime snack. Watermelon rinds can be pickled for a sweet and sour treat.
Watermelon is an annual crop. It will complete its full life cycle, including germination, reproduction, and death, in one growing season.
When saving seeds from watermelon, separate varieties by at least 800 feet or hand pollinate several fruits. A single watermelon plant can produce viable seed. However, to maintain a variety’s diversity over time, save seeds from 5-10 watermelon plants.
Watermelon seeds are held throughout the flesh of the fruit. As the fruits are eaten, seeds can be set aside for cleaning. Seeds should be rinsed well in a strainer or colander and then spread in a thin layer to dry on coffee filters, paper plates, or old window screens.
Store watermelon seeds in a cool, dark, and dry place and always keep them in an airtight container to keep out moisture and humidity. When stored under these conditions, watermelon seeds can be expected to remain viable for five years.