Watermelons Are Not Blooming

Soil

• Watermelons grow best in well-drained, slightly acidic, finely grained sand with a pH of 6.0 to 6.8. Heavier soils may cause watermelons to grow slowly and produce small fruit. Soil should also be properly fertilized. Do not grow watermelons in soil that has grown vine crops within the last three years, as the soil could be depleted of vital nutrients.

Temperature

• Watermelons are vulnerable to frost and require a frost-free growing season of 70 to 85 days, depending on variety. Ideal daytime temperatures of 70 to 80 degrees Fahrenheit and night temperatures of 65 to 70 F are ideal. Excessively high or low temperatures or early frost can prevent watermelons from blossoming and setting fruit.

Insects and Diseases

• Watermelons are susceptible to parasites and disease, particularly early in their growth cycle. Cucumber beetles, aphids and mites can devastate plants when present in large numbers. Watch plants carefully for signs of insects and treat them as early as possible. Various viral, fungal and nematode diseases can kill or stunt watermelon plants. Properly fertilized and rotated soil can help prevent disease.

Pollination

• Watermelons produce both male and female flowers during the growing season, though only female blossoms produce fruit. Female flowers need to be pollinated by bees to blossom and produce fruit. If the female flowers are damaged or bees are not present to pollinate them, fruit could be delayed or nonexistent. Protect the flowers from pests and encourage pollination by planting flowers near the watermelon vine to attract bees.