The Druid is in an area where there's no natural vegetation. He throws a pot with plant(s) in it under the enemy feet and casts Entangle. How would you rule it?
1) Make the druid hit an AC of 10 to hit the square he is trying to toss his plant into.
2 I'd limit the spell to a 5ft radius instead of the normal 40ft, the Entangle Spell says all tall grasses, weeds, and other plants to wrap around the creatures in the area. If the area only has the one small plant, and there isn't any other vegetation around, then he isn't getting a 40ft radius to his spell period.
What Traveon said, basically. Radius depends a little on the type of plant, too. A cactus would get you a lot less than, say, a vine or any sort of hanging plant.
For me all that's needed is a little vegetation for the spell to work fully. Using a potted plant is very smart. But of course the Druid has to care for the plant, otherwise he will lose powers for abusing nature.
My gut reaction was that I wouldn't bother with rolling to hit the square, but now I'm more inclined to have that work because I'm also thinking the area of effect should be more limited.
For what it's worth I've heard of this before, back in the 2E days I think and I've mentioned it to one of our druids in our Pathfinder game.
I wouldn't care about "abusing" a plant. Druid or not, it is just a plant. That's my take at least.
BTW. I don't remember seeing you post on Paizo Boards in the thread that spawned this one. Were you too afraid that they would call you a troll like me?