File this under "Projects to Impress Trick or Treaters." You'll attract hordes to your stoop, craning to see the only watermelon on the block that's wearing a pumpkin costume.
We are quite taken with how the gardeners at Babylonstoren, a resort in South Africa, manipulated a watermelon's shape by growing it inside a plastic box. Modeled after Japanese experiments with square watermelons, the creative team at Babylonstoren built a Perspex box with a debossed "B" on the inside. When the melon began breaking through the box, they harvested the square-ish melon; this is a DIY project we're dying to try.
Above: The watermelon, named "Sugar Baby" with an imprinted symbol of the hotel; photographs via Babylonstoren.
Above: The plastic box built by gardeners.
Above: You can start small, with a dwarf variety of watermelon, such as the real Sugar Baby variety ($2.99 for a packet of 30 seeds from Gurney's), and a pre-made acrylic box. A 300-millimeter-square Acrylic Container (which measures about 11.8 inches square) is $53.80 from Equipa Shop. Be sure to budget for an extra large candy supply, too; you won't want to anger the crowds by running out.
Above: Seen from above (L), the watermelon is sort of more, um, rectangular. But whatever. (N.B.: For other whimsical displays with edibles, see "Forget the Flowers: Vegetables as Decor.")