Herbalism
The primary gathering skill for Alchemy. Herbalism allows you to harvest herbs from plants, as well gives you the Find Herbs tracking ability.
The Find Herbs ability works at about half radar range. No herbs spawn within a short distance of roads and a wide radius around NPC towns. Each plant spawns 1-3 of each individual herb, and several plants spawn two types of herbs; for instance, Swiftthistle is only found on Briarthorn and Mageroyal plants. Each plant can usually be harvested only once, after which it disappears until it respawns.
Trainers
Journeyman: Brill, Undercity (Apothecary Quarter)
Expert: Undercity (Apothecary Quarter)
Artisan: Booty Bay, Orgrimmar, Feralas (Camp Mojache), Grom'Gol
Master: Booty Bay
Leveling
With the exception of Peacebloom and Silverleaf, all plants have a set skill level you must reach before you can harvest. You can possibly fail any gathering attempt, but may retry with no penalty. While hovering over the plant, the color of the “Requires Herbalism” text on the tool tip indicates the difficulty of harvesting the plant; if red, you lack the required skill level to harvest the plant.
Skill Levels
Earthroot: 25 (Unconfirmed)
Mageroyal: 50
Briarthorn: 70
Swiftthistle: Only found on Briarthorn and Mageroyal plants.
Bruiseweed: 100
Wild Steelbloom: 115
Grave Moss: 120
Kingsblood: 125
Liferoot: 150
Herb Locations
Areas are generally listed in order of the level of monsters found within, which also corresponds to the difficulty of herbs that may be found within.
Tirisfal Glades
Peacebloom – Open grass
Silverleaf – By base of trees.
Earthroot – Hilly areas.
Durotar
Peacebloom – Open areas
Silverleaf – Open areas.
Earthroot – Hilly areas.
Mageroyal – Very rarely spawns in the dried riverbed of Thunder Ridge.
Silverpine Forest
Nothing – A single bugged point for the Find Herbs skill, in the water on the northern tip of the lake near the road from the Undercity. A dot appears on radar, but nothing is found.
Peacebloom – Open grass
Silverleaf – By base of trees.
Earthroot – Hilly areas.
Mageroyal – By any area with freshwater, i.e. the lake to the east and the river that feeds it to the west.
Briarthorn (w/Swiftthistle) – On the patchy ground beneath heavily forested areas.
Bruiseweed – Rarely found by settled areas. Ambermill and Pyrewood each usually have one or two spawns, and the farms to the north can rarely spawn them.
The Barrens
This zone is worth a special note, as it's essentially divided into two areas. Lower difficulty herbs are found primarily north of the middle of the map, higher difficulty herbs are primarily found to the south of the Crossroads.
Silverleaf – Base of trees.
Peacebloom –The deeper green areas on your minimap.
Briarthorn – In the greenery in any oasis, as well as the thorny areas the Razormanes inhabit to the south.
Mageroyal – In the general area of any oasis, as well as the deeper green areas on your minimap.
Bruiseweed – Along the base of the hills the Slithid-infested areas touch.
Wild Steelbloom – Rarely on the tall mountains.
Grave Moss – On piles of bones within the depths of Blackthorn Ridge.
Kingsblood – In the middle of the Slithid-infested areas.