Tucking a watermelon seed into soil seems like a quick way to fill the garden plot with juicy melons. Watermelon plants require warm soil and plenty of sunshine to produce fruit. For this reason, gardeners often start seeds for three to four weeks in a protected inside location. Watermelon seedlings can be quite finicky and will fail at transplant without adequate warmth in the soil.
Plant in an area with ample room and full sun. These warm-weather plants cannot tolerate exposure to any frost. Each seedling should be planted at least 6 feet away from a neighboring plant. Avoid planting large seedlings older than three to four weeks to avoid transplant shock. Choose seedlings that have two to three healthy leaves for transplant to the garden bed.
Add compost or organic matter to the garden site after cultivating to a depth of 8 to 12 inches with a shovel. Mix amendments thoroughly into the soil.
Create mounded areas of soil about 4 to 6 inches high. One easy method involves creating a ridge of raised soil for spacing individual plants 6 feet apart. For individual mounds or elongated ridges, firm the soil after creating the planting site to limit soil runoff. Allow at least 7 feet between rows to allow plenty of room for the watermelon to produces leaves, foliage and fruit without crowding.
Place sheets of black plastic over the mounds and secure with a metal or wooden stake every 2 feet. Pull the plastic tight to limit weed incursion into the watermelon bed.
Cut a 5-inch cross mark in the plastic sheeting at the top of each mound with the utility knife. Peel back the flaps of plastic to expose the soil. Dig a small hole with a trowel to accommodate the roots of the seedling. The depth shouldn't exceed 2 to 3 inches. Allow room to accommodate the entire peat pot if you've planted seedlings in biodegradable peat containers.
Place each watermelon seedling into the hole and firm the soil around the roots. For peat pots, tear notches around the rim of the peat container and fold these sections back. Plant the entire peat pot below the soil level to eliminate any chance of the peat pot holding moisture away from the watermelon roots.
Sprinkle all-purpose fertilizer around each seedling and water deeply into the soil mound. Tuck the cut edges of plastic around the seedling to aid in warming the soil.