Fill a small pot with a well-draining potting soil. Watermelons are a warm-season fruit, and seeds will germinate only in warm soil temperatures over 60 degrees Fahrenheit.
Do not plant directly in the ground as the thick seed coats make germination difficult. Start the plant in a pot and transplant to a permanent spot.
Soak the potting soil well a day before planting. Press seeds into the soil at a shallow depth of no more than 4 inches. Place the pot in an area of full sunand water enough to keep the soil moist, not saturated.
Transplant into the ground once plants have produced three true leaves. This usually takes three to four weeks. Avoid waiting too long as transplanting older, larger plants leads to slow growth and poor fruit production, cites the Texas Agricultural Extension.