FruitWatermelon
Black Diamond Watermelon
Black Diamond Watermelon is an heirloom giant developed in Arkansas during the 1950s, prized for its striking appearance and reliable production across hardiness zones 3 through 13. Its deep, dark green skin contrasts dramatically with intensely bright red flesh, earning the 'Black Diamond' name and making it instantly recognizable in any garden. Reaching maturity in 90 to 99 days, these substantial melons can grow up to 50 pounds each, rewarding gardeners who provide generous space and consistent water. This open-pollinated, heat-tolerant variety thrives in full sun and produces seeded fruit that delivers the classic watermelon experience.
Photo © True Leaf Market
Growing Conditions
USDA Zone
3-13
Sunlight
Full Sun
Water
High
Soil
Well-drained, Sandy Loam, Fertile
Growth Stats
18 in
Height
TypeVining
Spacing
36
Plant Profile
Sunlight
Full Sun
Water
High
Zones
3-13
Size
18in H x ?in W
Growth
—
Care
High
Hover over chart points for details
Highlights
Black Diamond watermelons grown from open-pollinated seed can reach extraordinary sizes, with fruits documented at 50 pounds or more when given proper growing conditions. The contrast between the nearly black skin and vivid crimson flesh is stunning, making these melons as visually striking in the garden as they are at harvest. Its Arkansas heritage and heirloom status mean you're growing a variety that's been refined through generations of seed saving and selection for flavor and vigor.
Common Uses
Black Diamond watermelons are grown primarily for fresh consumption, whether sliced and chilled for summer eating or served at picnics and family gatherings. The seeded fruit is traditional watermelon eating at its finest: you select a ripe melon, cut it into wedges or chunks, and enjoy it fresh. The substantial size and high yield of individual plants make this variety particularly valuable for gardeners who want to preserve or share their harvest.
Growing Timeline
No timeline data available yet for this variety.
Care Instructions
Start Indoors
Start seeds indoors before transplanting outdoors. Watermelons have a long growing season and do best when started indoors rather than direct sown, giving you the advantage of an earlier transplant date and better odds of reaching full maturity before frost.
Transplant Outdoors
Transplant seedlings outdoors after the soil has warmed and frost danger has passed. Space transplants 36 inches apart in rows spaced 120 inches apart to give the vigorous vines and developing melons ample room.
Harvesting
Harvest Black Diamond watermelons when they reach full size and the skin has deepened to a nearly black color, typically at 90 to 99 days from planting. Look for a creamy yellow spot on the bottom where the melon rested on the soil. The melon should feel heavy for its size and produce a hollow sound when thumped. Cut the melon from the vine rather than pulling it, leaving a short stub of stem attached.
Growing Calendar
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Companion Planting
Ecology & Traits
Edible
Scientific Classification
Citrullus lanatus
Family
Cucurbitaceae
Genus
Citrullus
Growth Habit
Vining
Native Status
L48 (I)PR (I)
History & Origin
“Black Diamond emerged from Arkansas breeding work in the 1950s, developed during an era when American watermelon cultivation was producing ever-larger and more productive varieties. This heirloom variety represents the deliberate selection and cross-breeding work of mid-20th century gardeners and farmers who recognized the market and home-garden appeal of giant, reliable melons. Its open-pollinated nature means the variety has remained stable enough for seed savers to maintain it through generations, preserving the genetic work of those original Arkansas developers and allowing home gardeners today to grow the same melon their grandparents might have enjoyed.”