Surely you meant to specify a cactus (or cacti)?

ETA: OP -- sorry, to answer your question, I don't find it weirder to offer a therapist flowers versus anything else. I may be missing the cultural context here but I liken it to say folks (okay, me) bringing flowers when they're invited to family dinners and the like.

That said, if your therapist is the sort to get weirded out about anything outside the usual norms of therapy, then be prepared. If he is generally a go-with-the-flow kinda person, then what the heck, go for it and see what happens?

P.S. I haven't offered any of my therapists anything -- I cringe at the thought of paying them all the $$$ as it is and so, I haven't had it in me to even consider offering anything else (plus, none of them have done anything remotely above and beyond their normal call of duty and nor do I feel like I have a spectacularly special enough relationship with them to merit the extra stuff).