Squire James
Explorer
It's magic. It doesn't have to be logical or make sense. For me it works exactly like it says in the spell description - if there's plants, the spell entangles everything in a 40 ft. radius. Nothing more, but also nothing less.
All I need is to throw it at least 40 ft. from the enemy. not much accuracy required for that.
Well, being nit-picky about this matter encourages others to be nit-picky as well. For instance, "plants" implies more than one plant, so you'll need TWO plants in that pot. I know a DM who absolutely WOULD limit the Entangle effect to a single person if there was only one potted plant (the same guy keeps saying Invisibility and Mirror Image are useless against undead and creatures with Scent).
Personally, I would reduce the radius to something like 10 ft for the spell if a significant mass of plants is not present. A potted plant would not be enough, but you still get something out of the spell even with no plants. You can still throw the potted plant at them if you want...