Black Diamond

Watermelon

Zone 3b Save Garden

🌱 85d to harvest Vine

Sink your teeth into Black Diamond’s richly perfumed sweetness—an inky, dark rind that feels substantial in the hand and gives wa…

Crop Dates

Milestone	Date
Start Indoors	May 19th
Last Frost	May 19th
Transplant / Sow Outdoors	Jun 2nd
Harvest Begins	Aug 26th
Harvest Ends	Sep 21st

Crop Details

Trait	Value
Days to Maturity	85
Sun Requirements	Full Sun
Growth Habit	Vine
Support Needed	Trellis
Planting Depth	Normal
Germination Temp (°F)	70
Min Soil Temp (°F)	65
Min Night Temp (°F)	55
Harden Off (days)	10

Recommended Companions

French Breakfast 2 Radish

French Breakfast Radish

Frequently Asked Questions

Why are my Black Diamond plants suddenly wilting and developing fuzzy gray mold on leaves or fruit, and how do I fix it?

Fuzzy gray mold (Botrytis) on Black Diamond is usually triggered by cool, humid weather and crowded airflow. Remove any gray-moldy leaves or fruit immediately, water only at the soil line, and thin/spread plants so air can circulate through the canopy. If it’s spreading, start a labeled fungicide for edible eggplants/solanums according to the product’s directions and repeat as instructed.

How often should I water Black Diamond during the main growing phase, and what soil moisture should I maintain?

During vegetative growth through fruit set, keep the soil evenly moist but not soggy—aim for about 1 to 1.5 inches of water per week depending on heat and your soil, split into 1–2 deep waterings. Check 2–3 inches down: if it’s dry at that depth, water; if it stays damp, hold off. Consistent moisture helps prevent blossom drop and keeps fruits from developing tough, irregular texture.

How can I tell when Black Diamond is ready to harvest?

Harvest when the fruit is glossy deep black and about 7–9 inches long with a firm, slightly springy feel—typically around 80–85 days after sowing, depending on conditions. If the skin looks dull or the fruit feels hard and the seeds look prominent when cut, it’s likely past peak. Use clippers to cut the stem with a short piece attached to avoid tearing the plant.

Sink your teeth into Black Diamond’s richly perfumed sweetness—an inky, dark rind that feels substantial in the hand and gives way to a vivid, crisp interior. The flesh is exceptionally firm and juicy, with a smooth, fine-grained bite that stays satisfying from first slice to the last spoonful of summer. Ideal for picnic-style enjoyment, Black Diamond shines as a showy centerpiece for fresh sharing and as a standout choice for refreshing fruit salads and bright, fruit-forward salsas.

Sowing Tips

Transplant Conditions

Wait until soil reaches 65°F and nights stay above 55°F before moving outdoors. Harden off for 10 days first.

Direct Sow Preferred

Sensitive roots — does not transplant well. If starting indoors, use biodegradable pots and disturb roots as little as possible when moving outdoors.

Expert Note

For sweetest fruit, wait to transplant until soil is reliably warm and keep vines well-watered until flowering, then reduce water slightly to concentrate sugars.