Watermelon plants take up a lot of space, both for root room and above-ground, since the plant sprawls a lot as it grows. Most planter boxes are probably too small, but a 20 gallon pot/container size or larger (whether round, square, or rectangular) may support enough growth for a decent harvest (though a smaller harvest overall than a plant grown in the ground). Between using a large container and choosing a dwarf or compact-growing cultivar of watermelon, you can probably get some fruits to enjoy. Our Growing Melons web page includes tips for cultivating watermelon plants, if useful.

Miri