It's obvious why you jumped on it and paid immediately. That would have been quite a bargain for plants. Apologize to the seller for your rash payment and hope he/she would extend the courtesy to refund you as the seller did no wrong other than play victim to your greed. If anything your assumptions got the best of you.
Otherwise, there's no pay pal policy against ignorance so you'll likely go through a long process of documentation and series of correspondence to get your funds back in its entirety if you don't learn some humility real soon.
I didn't mean to be rude to him or anything, it was an honest mistake. I did email him back already, apologizing and asking for a refund. It was my fault, I should've read the rules before rushing into it.