Black Diamond Watermelon
Light requirements: Full sun.
Planting: Space 36 to 60 inches apart. (Read the stick tag that comes with the plant for specific spacing recommendations.)
Soil requirements: Provide well-drained, nutrient-rich soil that’s high in organic matter. Work at least 3 inches of organic matter into planting beds—more is better. Soil should be at least 70ºF at planting.
Water requirements: Keep soil consistently moist until fruits are about the size of a tennis ball. After that, water only when soil is dry. Avoid overhead watering to beat foliar diseases; use soaker hoses instead. About a week before fruits are ripe, water only if leaves wilt. Withholding water at this stage concentrates sugars in fruit.
Frost-fighting plan: Even a very light frost (31 to 33ºF) can kill watermelon vines. Use frost blankets or cold frames to protect vines and prolong the harvest season. To ensure fruits ripen before frost, remove any blossoms that start to develop within 50 days of your area’s average first frost date.
Common issues: Pests to watch out for include melon aphids, along with spotted and striped cucumber beetles. Fungal diseases such as alternaria leaf spot, gummy stem blight, anthracnose, downy mildew, and powdery mildew can attack plants.
Harvesting: Harvest when rind changes from bright to dull green, and the part that touches soil shifts from greenish white or straw yellow to rich, creamy yellow. Rap on the skin and listen for a low-pitched thud; tune your ear to the incorrect sound by rapping on a few fruits that aren’t ripe. Underripe fruits resonate with a high-pitched, tinny sound. Cut melons from the vine, leaving about an inch of stem attached to prevent rotting if they’ll sit before use.
Storage: Watermelons keeps 2 to 3 weeks unrefrigerated. Place in a cool area, such as a basement, to increase holding time. After cutting, refrigerate unused portions. If you have extra melon on hand, dice or cut the flesh into balls and freeze.
For more information, visit the Watermelon page in our How to Grow section.
- Calories: 46
- Carbohydrates: 12g
- Dietary fiber: 1g
- Sugars: 10g
- Protein: 1g
- Vitamin A: 18% DV
- Vitamin C: 21%
- Potassium: 5%
While watermelon is quenching your thirst on a hot summer’s day, it is also providing a good amount of vitamins C and A, antioxidants important in fighting disease, as well as potassium, believed to help control blood pressure and possibly prevent strokes. Red-fleshed watermelon is high in lycopene, another potent antioxidant with cancer-preventing properties. The yellow-fleshed variety is high in beta-carotene, likewise a powerful disease fighter. Lycopene and beta-carotene appear to work with other chemicals in fruits and vegetables to provide health-supporting effects.