Watermellon, Black Diamond
This old standard variety generally reaches the thirty to fifty pound range. The fruit is slightly oblong with prominent creases, and dark skin. In cool climates, watermelon seeds should be started indoors, but no sooner than a month before transplanting; plant three seeds per peat pot, 1/4 deep. Provide heat to keep the soil at least 80-85 degrees F. Cut off all but the strongest seedling as soon as true leaves appear, and transplant about a week after frost; put two or three plants in each hill with a 6-8' space in all directions.
Gardeners in warm climates will be able to direct sow watermelons as soon as the soil temperature reaches at least 75 degrees F, planting six seeds per hill with 6-8" of space in all directions. Thin to the strongest two or three plants as soon as the seedlings appear. Watermelons should be planted in full sun and rich, loose soil. Young seedlings may benefit from black plastic to warm up the soil. As soon as the vines begin to develop, apply a thick layer of mulch to control weeds and protect the melons from soil contact. Keep the soil moist until the fruit begins to grow, then water only if the soil dries out completely. Watch out for insect pests, which can be a problem.