Erm, yeah, this looks...pretty good, actually. A couple of things, though:
Drop Mystic Box. Unless you have a very specific reason for wanting that monster on your opponent's field (and let's just say that Cephaltous' attack power boost is an iffy one at best) then your better of just using a one-for-one destruction card like Smashing Ground or Fissure. Soul Taker if you want to specify the target that badly. Also, Regenerating Rose is icky, so drop it. It's terrible to draw into and the tokens are too weak to be useful but too strong for Crush Card fodder. You've already got Dandylion to set up double tokens and to swap to your opponent, and Gigaplant to spam it back up from the graveyard as many times as you need it. Seed of Deception also looks redundant here; you have very few targets for it and Lonefire Blossom isn't even one of them. A few cheap synchro summons just doesn't seem worth the the deckslot. Trunade also looks iffy since it clashes with both World Tree and Plant Connection. Between Camellias, Solemn, and Polynosis you're already packing a heckuva' lot of negation, so your opponent's backfield shouldn't be a very big concern at any point of the game. Also kind of iffy on Mark of the Rose since this looks more like the kind of deck that just wants to overrun your opponent while using heavy negation to prevent them from putting any answers on the table; not one that enjoys pitching your opponent's monster back and forth. Surely, Brain Control would be more in-tune? It would also help you put the required number of level stars on your field if you find yourself stuck with Copy Plant or Nettles and little else on the monster front. The more I look at them, the more I also find three copies of Botanical Girl to be redundant. It's a nice enough search effect, but it's also pretty picky with its timing since it's effect is optional (sacrificing it for any of your support cards would not trigger the effect :\) so I'd say drop a copy, maybe even two. Also, strong as it is, I just can't see Torrential Tribute paying off very much in a deck that's so good at keeping large amounts of monsters on the field, so I'd suggest going without it here. I'd also drop Copy Plant down to one. It's puny, so you'll only ever want it if you're all set for a synchro summon, also - on account of having a full zero-zero - it's highly searchable; you've got both Lonefire and Botanical to pull it out of your deck and a whole bag of tricks to pull it out of your graveyard, so you should have no problem accessing it when you need it. Finally, Fragrance Storm is a bit on the flimsy side, imo, becoming a -1 for you unless you draw a plant. (and even then, it will only break even and is slower than your average destiny draw since it needs to have the monster on your field); I'd suggest leaving it be for other draw effects.
So, suggested drops in short:
-1 Botanical Girl
-2 Copy Plant
-1 Fragrance Storm
-1 Giant Trunade
-1 Mark of the Rose
-2 Mystic Box
-1 Regenerating Rose
-1 Seed of Deception
-1 Torrential Tribute
In exchange, I'd really suggest putting Hand Destruction in here. It will help you feed some plants to your graveyard in the early game so they're ready for revival and lets you see some fresh cards from your deck. Also, precisely because the graveyard recursion engine is really the big thing in this deck, Card of Safe Return would probably benefit you a lot. Extra copies of Polynosis would also help you enforce the negation trap even tighter and Enemy Controller would give you some protection/battle aid in the early game while letting you steal monsters with impunity in the lategame. Suggested additions in short:
+1 Brain Control
+2 Card of Safe Return
+1 Enemy Controller (a third Pollinosis is also an option)
+3 Hand Destruction
+1 Pollinosis
Also, if possible
+1 Red Dragon Archfiend
Red Dragon is good muscle and can clear out any annoying walling types so they won't slow you down; no reason not to keep one copy around just in case if you can get one as you won't be needing all of those monsters in threes anyway.
Overall...I'm liking it. This deck is really almost as much control as it is swarm, so once you get your engines in place, it's pretty much over for your opponent unless they pull a truly miraculous reversal. The biggest weak I can see here is that this deck has a pretty slow start. Until you get a Lonefire Blossom or other handy recurrable monsters into your graveyard, Gladiator Beasts will be giving you a really rough time, tagging in and out as they please while trampling your monsters with impunity. An early-game Cephalouts can keep them in check, but the sooner you get your Gigaplants out there the better. Overall, this plays very similarly to zombies, but with a slightly slower start compensated by a bigger control element. You've also got a big beatstick in Carmellia, allowing you to run over many monsters that would cause trouble for zombie.
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