Personally, I think that you can drop the region lore. Knowledge of the herb would include guidelines on type of area/terrain where it is found.
In fact, since the herbs come with codes, you could use that to determine what herbs and what type of herbs that the player knows about. You do this by limiting the player to only herbs from the terrain and climate types of where he grew up, and have each rank represent the difficulty modifier (i.e. with 8 ranks in herb lore he knows about herbs from his region with a rating of 8 or less), all without requiring skill rolls.
If the player wants to see if his character knows about another type of herb from out side his region, then he would need to roll. (and keep track of which ones he knows about).
As his skill in Herb Lore goes up, allow him to branch out to other regions, again going up the difficulty scale with more ranks.
I hope that makes sense...
Another way to do it would be to require 2 ranks for each difficulty number for local region with an additional 2 ranks for herbs from outside home region of same difficulty. (i.e. 2 ranks to know about herbs with difficulty of 1 from terrain/climate like home, and 4 ranks to know about herbs with difficulty of 1 for other terrain/climate combinations. As above, not requiring a roll for things in the Known ranges, only requiring it for things outside the known ranges.
(I.e. as a GM, determine if and what herbs will be found in an area BEFORE the players begin their search. Then they search, and if they find something inside their knowledge range, good. If they find something outside it, they make an Herb Lore roll to see if they recognize it.)
