Well if others are getting use out of her then maybe I just haven't learned the trick to her just quite yet. My concern was that, since a last-minute conversion or desecration can be so powerful, no one really minded her lack of early utility. But perhaps I spoke too soon.
The problem with buffing clearance, though, is that it's so potent as a last-minute gambit - a free +40 MP pool in the middle of a boss fight as long as you haven't used sanguine - that any improvement would lead to utter ridiculousness. Of course, that does mean that her early worshipers get a raw deal on using the boon for its original purpose. I'd suggest reducing the number of plants she spawns, but since her prep "penalty" is often viewed as a benefit I'm not even sure whether that would help or hurt. Maybe I'll just leave the Earthmother discussion to the Earthmother users.