Plant watermelon from late spring to early summer, once soil temperatures reach 70° F or above. Space watermelon 3 to 5 feet apart in nutrient-rich, well-drained soil with a pH of 6.0 to 6.8.
Many types of plant seeds benefit from pre-planting soaking to soften the outer seed coating and hasten germination. However, watermelons are an exception to the rule. Soaking the seeds before planting increases the risks of various fungal diseases, such as anthracnose caused by the Colletotrichum lagenarium fungus.