Very impressive - excellent work. I love the look of the layout and the plant art is very nice. Ironically I started to create a similar document once I'd read that herb lore didn't make it into Box Set 2. I put it on hold until I get the Box Set 2 game guides. I came up with different plants though -Brecilian Beard, Bronto Brush, Ferelden Finger and Storm Sedge to name a few. I did come up with Dragonbane, which sounds like it may be a bit like your Dragon Thorn. I've only glanced at your plant listings - so I can't say yet.
One thing extra I did, is I attempted to define geo-climatic regions for Ferelden and create a 3-tier ranking system for the occurence of beneifcial plants, minerals and gems within them. So far I've come up with about 10 regions - Lake Calehad District, Breclian Forest and Northwest Coastlands to name a few. I didn't get too elaborate with it and only came up with "Common Throughout Ferelden", "Common to [said
] Area(s)" and "Rare" as the rarity/occurrence categories. I actually used the vender inventories from the 2 Dragon Age CRPG's to determine some of that. The purpose of it, is that a GM could use that information for test rolls for the occurrence of beneficial plants, minerals & gems in an adventure area and even build quests around the rare varieties. I was basing the Player identification of plants on Cunning (Natural lore) rolls and their discovery in a given area on Perception (Seeing), Perception (Searching) and Perception (Smelling) rolls.
Will the team that created this consider an update in the future. And if so, will it be possible for others who may wish to collaborate efforts to join?