Vile Mushroom

One purpose: powder. That powder is half the recipe for Worm Food, so a corrupted surface is really an Eater of Worlds summon farm with mushrooms growing on it. Any swing from any tool knocks one loose, and a sickle pulls hay out of the same swing if you want the extra material.

They regrow on corrupt grass, but only where the background is either untouched or completely bare. Seal your farm strip with your own bricks and nothing comes back, which catches a lot of people building tidy underground plots. Cleaning the area with purification powder or a clentaminator is the other way to lose a patch: the plants convert into ordinary mushrooms and jungle spores rather than dying, and the grass under them stops producing.