Find Herbs

Here is a list of the required skills for the herbs:

Peacebloom = 1
Silverleaf = 1
Earthroot = 15
Mageroyal = 50
Briarthorn = 70
Stranglekelp = 85
Bruiseweed = 100
Wild Steelbloom = 115
Grave Moss = 120
Kingsblood = 125
Liferoot = 150
Fadeleaf = 160
Goldthorn = 170
Khadgar´s Whisker = 185
Wintersbite = 195
Firebloom = 205
Purple Lotus = 210
Arthas`Tears = 220
Sungrass = 230
Blindweed = 235
Ghost Mushroom = 245
Gromsblood = 250
Golden Sansam = 260
Dreamfoil = 270
Mountain Silversage = 280
Plaguebloom = 285
Icecap = 290
Black Lotus = 300
felweed= 300
dreaming glory= 325
mana thistle = 350
nightmare vine = 370
goldclover = 350
Talandra's rose = 385
adder's tongue = 400
tiger lily = 400
frozen herb = 415
icethorn = 435
lichbloom = 435

Specialty herbs:

Swiftthistle - only found attached to mageroyal or Briarthorn
stranglekelp - any water, I have found this is zones with level 50s
winter's bite - only in alterac mountains near the ogres
icecap - only in winterspring
ghost mushroom - special caves - maradoun, hinterlands are common places
grave moss - only on graves - duskwood, wetlands are common places

Black lotus - rarest of the rare - the only current green herb, this is found in EPL, Burning Steppes, Winterspring and silithus. This only spawn 5 at a TIME in the WORLD. Each zone it spawns only holds a maximum of 10 spawn points. There is a 12-24 hour respawn time on each spot.

Find herb is a track spell, that you will get when you learn herbalism. Only one track spell can be active at the time, and they will automatically be turned off when you die. - Changed with current patches

The track spell doesn't improve, so you will be able to track high level herbs as soon as you get it.
You'll still need to improve your herbalism skill to pick higher level herbs.