Square pumpkins are a thing. You basically grow the pumpkin in a clear box and the pumpkin takes the shape of the box. I'm sure there is more to it than that but I'm currently working on that premise. I have a veg plot and some pumpkins and a way to make clear plastic boxes so I thought I would give it a shot.
The box is made from 5mm acrylic sheet, 3 of them. They should be sturdy enough to resist the slow onslaught of growth from a pumpkin. Because acrylic sheet is fairly expensive (£8 a sheet) I decided to cut a prototype of the box first. This is where different material thicknesses really win out, I used 2mm mdf and simply scaled the box down to 40% of it's original size. The test piece worked fine first time and although it was a slightly snug fit the full size version worked a treat too. (svg here)
35 Projects/ 44 weeks