Minecraft wiki entry for Cactus, associated text: A natural one block tall cactus.
A natural two block tall cactus.
A naturally occurring unusual four-block tall cactus.
Another naturally occurring unusual four-block tall cactus.
A natural five block tall cactus.
A naturally occurring rare six-block tall cactus.
A natural eight block tall cactus, extremely rare.
An improbable natural nine-block tall cactus.
A twelve-block tall cactus, extraordinarily rare.
A natural nineteen-block tall cactus.[3]
A natural twenty block tall cactus.[4]
A natural twenty-two block tall cactus, the second tallest known cactus.[5]