From the Super Mario Wiki
Growing Potion is a red concoction that is capable of enlarging its target to numerous times its original size. Not much is revealed about Growing Potion, but it seems to serve mainly as an antidote to Shrinking Potion and probably has similar attributes. It is assumed to be created by Waldo the Wizard, who is capable of conjuring up a flask of it with little effort.
Growing Potion makes its first and only appearance in The Super Mario Bros. Super Show! episode "Princess, I Shrunk the Mario Brothers". After Toad accidentally shrinks Mario and Luigi with Shrinking Potion, he is tied up by King Koopa, along with Princess Toadstool and Waldo. Eventually, Princess Toadstool, Toad and Waldo break free of the chairs to which they are tied, and Waldo conjures up a flask of Growing Potion.
Toad then takes the Growing Potion and secretly inserts it into the spray gun that King Koopa initially used to spray pesticide at Mario and Luigi. When King Koopa corners Mario and Luigi in Waldo's greenhouse, he sprays them and some potted vegetables. Not only do Mario and Luigi grow back to their normal sizes, but the nearby vegetables also grow large as well. Taking advantage of the situation, Mario and Luigi use the enlarged vegetables to scare off King Koopa and his Koopa Troopas.