For the record, I believe you got the Seed from defeating Smilax, and the Fertilizer was given to you by the Shyguy in Nimbus Land. Then you go to Rosetown and you guys know the rest. Also, the Lazy Shell Armor is the best if you use it right (put it on Peach, and make sure she has the infinite rock candy item you get in the Casino). That way, you pretty much can't die, and you unleash a lot of damage on everything every turn. Then, when you feel the need, you just resurrect your other party members and lay a smackdown.
On topic, I'd rather have Mallow *ducks*, but I'll take either if we can get them.