I can't figure out how to beat the plant boss... Does anyone know what attacks work the best on him? Thanks!

use fire or 2nd lvl blizzard

if you re lucky and get 3 blizzard u get a chance to freeze it solid

when you see the casting circle on the ground run away

when you see it rear back run in circles

when you see it rear back and green gas in it's mouth get out of the way

or just hope you have clear and cure and youll be fine.

in second and third runs, same tactics but more care

Thank you!

have gnash lead the groop, his ranged atks are best for the flower boss, exit the dungeon and head to Rebena Te Ra, and aquire, through purchus or synthesis, the best possable weapon for gnash, after he first joins your team. that's my advice, i hope(takeru(TK) takashi from digimon addventure 01) that it is of some help to you.

since when was this the 2nd boss? its the 3rd anyway just do what voice of reason said.

@anonimus why Gnash yuri is the best for it just wait for the flower to expose its crystal and jump up and kepp doing chains on it after 2 chains jump off and repeat.

How I did it:
First, kill the two tentacle things in any way you feel like(I used yuri). The flower will then open. Jump inside it and slash it a few times with Yuri, and hop off of it before it spins. IF you were too weak to kill it before the tentacles come back, simply kill them again and repeat.