Super Seeds are magical seeds which grow larger than normal crops which regrow instantly after being harvested.
Cosmo, Wanda and Poof used them to make Mr. Turner's farm better, but as super-seeds are immune to magic, Timmy couldn't undo the wish. Fortunately for Timmy, the super-seeds met their arch-enemy: Dad. With his lack of farming skills and lethal touch, every super-crop he harvested died. If super seeds are fed to animals, they will grow huge as well.