The fight would presumably play out something like this:

The poison plant will emerge from one of 3 pipes in the centre of the room, and slowly creep back into the pipe. It’s 3 heads will then individually shoot up all 3 of the pipes in the small, boxed in arena and shoot purple, bubbly projectiles in a clockwise motion.

Whilst this is going on, poisonous mushrooms will drop down from the ceiling, meaning you have to be extra careful whilst running around the arena.

Then the heads will go back inside the pipe and all 3 will appear in the middle pipe again. This gives you 5 seconds to jump on the plant and take some of its health away.

This will repeat until the 3rd hit, where more pipes will appear from the walls. When the heads attack, they will individually appear in a random pipe, and once they shoot a few projectiles they will emerge from a different pipe. This will go on at least 3 times before they become vulnerable to being stomped on. The poisonous mushrooms will stop dropping from the ceiling once this phase is reached.

Once they have been hit 5 times, the boss fight will be over.