Black Diamond watermelon is a popular watermelon variety among home gardeners. Black Diamond watermelons get their name from the plentiful dark seeds that cover the deep, red flesh of these juicy watermelons. By the time these watermelons are ready to harvest, they may be as large as 75 pounds and well over 1 foot long. Gardeners who plant Black Diamond watermelon seeds can anticipate a delicious watermelon harvest late in the summer.
Prepare the sunny growing area in the spring when the soil has warmed to at least 65 degrees F. Use the garden spade to work the soil down to a depth of at least 8 inches. Add 4 inches of compost to the top of the soil to enrich it. Work the compost into the soil with the garden spade and rake the soil surface smooth.
Make planting rows for the watermelon with the hoe. Space the rows between 5 and 8 feet apart and make the rows 1 inch deep.
Place the Black Diamond watermelon seeds into the prepared rows. Space each seed between 3 and 5 feet apart. Cover the seeds with 1 inch of soil.
Water the seeds generously immediately after planting.
Cover the seeds with mulch to insulate the soil and keep it warm.
Keep the soil evenly moist while the Black Diamond watermelon seeds germinate. It will take approximately one week for the seeds to germinate.
Pull back the mulch from the seedlings once they emerge from the soil. Leave the mulch on the soil surrounding the seedlings to conserve soil moisture and prevent weeds.
Provide at least 1 inch of water each week for the watermelon plants if sufficient rain does not fall.
Begin applying fertilizer to the watermelon plants after they are at least 4 inches tall. Apply the fertilizer to the soil around the watermelon plants twice per month.