Question: Can I grow watermelons in western Illinois?
Answer: Watermelons are not frost hardy and require a long growing season with relatively high temperatures. Daytime temperatures between 70 and 80 degrees F and nighttime temperatures between 65 and 70 degrees F are ideal. Watermelons grow well in both humid and semiarid areas, but you may find foliar diseases a problem if you have a humid summer. You might consider using black plastic mulch to conserve moisture, suppress weed growth, and warm the soil. Plants or seeds should be spaced two to a hill, three to four feet apart, on the strips of plastic placed on five-foot centers. Start your seeds in peat pots or pellets about four weeks before the anticipated planting time. Watermelons also may be direct-seeded through holes cut in the plastic, but this may delay the harvest.