Seedless watermelon seeds are actually regular watermelon seeds that have been treated with a special chemical that makes them sterile. A seedless watermelon plant still needs to be pollinated by a regular watermelon plant, so most seedless watermelon packets will include both seedless and seeded watermelon seeds. However, it is wise when planting seedless to make sure you have planted at least one seeded watermelon variety with it. Watermelons need warm soil to germinate, so start the seeds indoors to get a jump on the growing season.
Put a masking tape label on each plastic seed tray, marking one seedless and one seeded.
Soak your peat pellets in lukewarm water until they expand, and then place them in a plastic seed tray. Allow the peat pellets to sit for four hours before planting seeds into them.
Insert one to two seeds, 1 inch deep, into each peat pellet, and scrape some of the pellet dirt back over them. Plant the seedless seeds in the pellets on the seedless tray, and vice versa.
Cover the trays with plastic wrap and place them in a warm, bright location with daytime temperatures of at least 70 to 80 degrees F. When half of the seedlings have emerged, remove the plastic wrap.
Move the seed trays to a sunny window and ensure that the temperature remains between 70 and 80 degrees F.
Plant the seedlings in the garden approximately three weeks after sowing the seeds indoors. One week before transplanting, loosen the garden soil to a depth of 6 inches with a rototiller or hoe and shovel. Cover the watermelon growing area with black plastic to help warm the soil. Remove the plastic before planting.
Mound up a hill of soil that is approximately 2 feet in diameter and 1 foot tall. Pour 2 inches of compost or manure over the entire hill and work it into the soil with a hoe. Compost can be found at any nursery or lawn and garden center.
Cut the netting on the bottom and sides of the peat pellet with a sharp knife. Dig a hole in the mound that is just slightly larger than the peat pellet and insert the pellet into the soil. Pack the soil around the root system of the seedling. Dig another hole in the mound and plant a seeded watermelon variety.
Repeat steps 6 and 7 for additional seedlings. Space mounds 6 feet apart, and space the rows 4 feet apart if you have more than one row.
Keep the soil moist, but not overly wet.