We would say it is about 90% successful. We tried our hand at growing a square watermelon and this is what we ended up with. All you need to do is put the watermelon in something and it will grow to that shape. In this case we used a cinder block or brick to grow a square watermelon. As you can see in the picture we had to break the brick off the watermelon. It was pretty neat as you could just slice you a piece off like a loaf of bread.