Floro Sprouts are important items found in Super Paper Mario. Floro Sprouts can be planted into different beings (often without the being even knowing), and once the plant grows enough, they can brainwash the being they are put into. The brainwashed beings serve whomever put the Floro Sprout into them, making them mindless servants.
The Floro Sprouts ultimately control their victims, but their effect is different on different people. Controlled Cragnons completely obeyed the Floro Sapiens that used the Floro Sprouts, and would even die for the Floro Sapiens while possessed. When Luigi was controlled by a Floro Sprout, he still had slight control of his hand movements, trying to break free. When O'Chunks was controlled by a Floro Sprout, his battle strategy was improved and he got even stupider. O'Chunks, now called O'Cabbage when controlled, could only shout the names of vegetables. The will of the victim may have some role in determining how well the Floro Sprouts control them.
Inventor and Intended Purpose
Floro Sprouts were invented by King Croacus IV. The Cragnon people near by the Floro Sapiens were polluting the water, tainting the only food supply of the plants. King Croaucs IV became insane with the water being polluted, and so he wanted revenge. He created hundreds of Floro Sprouts that his servants would put into the minds of the Cragnon people. The goal of the Floro Sapiens was to have complete control over the Cragnon people, turning them all into Floro Cragniens.
There were multiple reasons why the Floro Sapiens and King Croacus IV wanted the Cragnons controlled by themselves. The first reason was so that they would not pollute the water. With the water unpolluted, the Floro Sapien race could thrive again. The second reason was so that they could dig for gems. King Croacus IV was obsessed with gems and beautiful things, and so many Floro Cragniens digged for gems King Croaucs IV would keep. The third and final reason was so that the Floro Kingdom could have some more servants. It is likely that the Floro Cragniens would do all of the busy work and so the Floro Sapiens could relax.
In Chapter Five, the chapter that held the Cragnons and the Floro Sapiens, not only the Cragnons get controlled. In the latter part of Chapter Five, the first three Heroes of Light find Dimentio and O'Chunks. Dimentio has put a Floro Sprout in O'Chunks, turning him into O'Cabbage. O'Cabbage is stronger and smarter than O'Chunks in terms of battle strategy, but O'Cabbage can only shout the names of vegetables.
After defeating O'Cabbage, the Floro Sprout comes off of O'Chunks head. O'Chunks turns back to normal and then leaves. Mario picks up the Floro Sprout and puts it on his head, not turning into a mindless slave. The Floro Sprout presumably died when O'Cabbage was defeated, but it looked as normal as ever. With a Floro Sprout, Mario was able to access two new parts of the Floro Caverns he could not before. Besides for entering those two places, the Floro Sprout is not needed anytime else. The Floro Sprout can be worn or taken off at any time, staying in Mario's important items.
Chapter Eight Use
In Chapter 8-3, Bowser and Princess Peach were separated from Mario and Luigi. The two brothers found Dimentio, who told them about Count Bleck's secret plot. Dimentio asked the brothers if they were to help him. If the player chose yes, Dimentio would plant two Floro Sprouts in Mario, possessing both of them. Luigi already had a Floro Sprout, but the player does not learn this until after defeating Count Bleck. The player would get a Game Over if this happened.
In Chapter 8-4 when the Heroes of Light destroyed Count Bleck, Dimentio came in and stole the Chaos Heart. It is revealed that Dimentio planted a Floro Sprout in Luigi earlier and Luigi becomes Dimentio's puppet. Dimentio can now combine himself, a controlled Luigi and the Chaos Heart to create Super Dimentio. It is said in the Dark Prognosticus that the man in green (Luigi) would for some reason wield the Chaos Heart, and the Floro Sprout is the reason why. Dimentio might have some sort of alliance with the Floro Sapiens, since he somehow has obtained three Floro Sprouts.