Well, that's obviously a question of balance, Ryfte. It's a good argument to change how the spell worked, but if ImperatorK was asking for how the rule should be interpreted, I think it's difficult to say that that's currently how it is written. I'd personally argue that inherent in Druid spells is that they are strong in natural areas, and weak in man-made areas, much like Cleric spells inherently have limitations based on the faith of the cleric, but that's obviously just a matter of opinion, which is entirely up to the GM in question.
Regarding the plant pot, Imperator, I don't think it's of much use. If your GM agrees that it creates plants, the plant in the pot is superfluous. If he doesn't, I don't see how the requirement to have plants is satisfied by a single plant which isn't affixed to the ground (beyond what that plant can do, obviously). The last line in the SRD text does seem fairly clear that the effect of the plants depends on the vegetation that is present, even if you don't like my interpretation of the "Area" line. There really isn't any language to signify that an base amount of plant material is required to "grow" to fill the area, at any rate. That is more just interpretation based on how you'd like the spell to work.