Watermelon plants are wonderful to grow for even the most inexperienced gardener. Simply popping the seed into the ground seems all that is needed in all the right settings. One of the problems of growing watermelons is the amount of space they need. This can be a challenge, especially if you are trying to garden in raised beds, but quite possible with the right amount of care and attention.
Inspect the overall plan of the raised bed garden. Plant the tallest plants at the northern-most end of the garden since the sun travels across the garden east to west (in the Northern Hemisphere). Plants on the southern side will shade the plants behind them if they are too tall. Watermelon is only about 6 inches high, so look for a spot close to the edge on the northern end of the raised bed.
Plant watermelon seed or seedlings about 6 inches in from the edge of the barrier and just about 1 inch down. Firm the soil over the seed. Forming a hill for planting isn't necessary since the raised bed provides adequate drainage.
Keep the soil watered and weeds removed. Watermelons' roots extend several feet down, so give them at least two gallons per plant.
Train the stems as soon as they start to grow out of the raised bed to ensure that they are growing in the intended space. Remove any tendrils that are growing out of the space. Apply a layer of hay to keep the plants protected from the damp ground and to discourage weeds.
Harvest the watermelons when the stems start to brown and the melon has a hollow sound when it's thumped.