With the arrival of the Wrath of the Lich King expansion Herbalism has become a primary gold making profession, since the herbs are very much in demand for Inscription. For a far more detailed guide to leveling all of the WoW professions, check out Penn's Guide.

A note on levels: With the 3.1 patch the same level requirements that the crafting professions have now applies to the gathering professions. Certain twinks (level 19, for example) were able to level their herbalism skills to 450, by being summoned to higher level areas, to get the nice heal. Now, you actually have to be level 55+ to get max level herbalism.

This guide can be used by someone who is leveling up as well as someone just leveling their skill. If you're leveling up just be aware of the level requirements.

Suggested Addons
Herb Picking 101
Herbalism 1 to 350
Herbalism for Inscription
Herbalism in Northrend
The Ultimate Professions Guide
Addons
For all of your gathering we highly recommend that you grab the Gatherer Addon. This comes with a WoWhead database of herbs (and other gatherables.) This will allow Gatherer to display the know location of the herbs on your main map, making your collecting routes easy.

A mapping addon, such as Cartographer, is also a great idea. It allows you to mark up the maps with your own notes, among other things. Gatherer works very well with Cartographer.

Herb Picking 101
Stay in one area and get your skill as high as possible before moving to the next area. If you don’t do that you will find many herbs in the new area that you just won’t have the skill to pick. When you’re in any particular zone set your mini-map to show herbs and do loops around the area. The herbs will show as yellow dots on the map.

Once you have your apprentice Herbalism skill go to your favorite starting area and start gathering Peacebloom and Silverleaf. I went to Eversong woods, but these herbs are all over the place in all of the Horde and Alliance starting areas.

Once the herbs in your area aren’t given you any skill improvements you’ll want to go to the next higher zone. I went to the Ghostlands, but the Barrens. Westfall, and Loch Modan are good areas, too. As I mentioned above, if you move on too soon you won’t have the skill to pick anything.

Most of the herbs on this list are the ones you will need for Inscription, so you can level this skill and build your herb stash at the same time. Or sell it all and make quite a bit of gold.

Also note, that as you level up this skill you will gain a small heal, lifeblood, which increases as you level your skill.

Herbalism from 1 to 350+
1 - 50 Silverleaf and Peacebloom

These two herbs are all over all of the starting areas for both sides.

Horde can run a path through Mulgore, it's easy enough to just make circuits round the base of Thunderbluff grabbing all the Silverleaf and Peacebloom in sight. The same is also true for Durotar, but Mulgore is better. Eversong Woods may be the best of the Horde areas, even better than Mulgore.

Alliance will want to hit up either Dolanaar going down south east or so around the lake before heading back to complete the loop. An alternative is just making complete runs of Elwynn Forest or any of the Ally starting area. .

Undead will want to target Solliden Farmstead first, running north through the mills and looping around back south towards Stillwater and onto Cold Heart Manor + Nightmare Vale and finally back to Solliden for a complete circuit.

51 - 70 Mageroyal and Earthroot

Horde will start in the crossroads, heading immediately west and then north right before the entrance to Stonetalon, browse around the Harpies zone a bit before running back east to the Gold Road and south once again to the Crossroads.

Alliance can start in northern Westfall, following the coast down south towards Deadmines before turning to run over in the direction of Sentinel Hill, to complete the circuit run back up north again.

Another spot is Gol'Bolar Quarry in Dun Morogh, just make full circuits.

Alternate areas are: The Ghostlands, Silverpine Forest, Westfall, and and any are for levels 10-20.

71 - 100 Briarthorn

This'll be running the same path as the above Horde Route, this time however you'll extend it east to the Sludge Fen and should you so desire it possibly the entirety of the Barrens, allowing you to grab everything you need for this skill level..

Undead will be doing Southern Silverpine Forest, Pyrewood on down to the Hillsbrad Foothills entrance and all the way back for a complete circuit.

Alliance can either maintain the same route as previous or expand into doing circuits throughout Twilight Grove located in Duskwood. Another few possible paths are both circuits of Lakeshire - Redridge, Darkshore, and Eastern Loch Modan.

101 - 115 Bruiseweed

Horde will start at the Ashenvale Ramparts and head north-east towards Splintertree Post, make sure to run a wild path rather than follow distinct roads and such, alot of the herbs are out there in the forest and not so easily located as before. Once you hit Splintertree head west towards the bridge and south around the moonwell, turn here for the final part down to the Ramparts and you've completed a circuit.

The Stonetalon Mountains are viable, hit up Camp Aparaje, head west from there towards Grimtotem Post, south to Malaka'jin, and finally east to the Greatwood Vale before returning to home point. Another path is The Field of Giants, southern barrens inbetween the razorfen dungeons. Windshear Crag contains various herbs should you desire to go there as well.

Alliance can go North of Mystral Lake or West of Astranaar for various herbs in Ashenvale. Other spots are making circuits round' the Stonewatch Keep in Redridge Mountains and the Eastern Coast of Loch Modan for dwarves.

116 - 125 Wild Steelbloom

Horde can head for Stonetalon Peak once more and run circuits round the Druid Grove and Talon Den, another would be running back and forth between the Field of Giants and the Razorfen Dungeons again. Also down there is a few paths through Thousands Needles, start at the great lift and head for Highperch before returning.

Alliance & Horde can both try out Arathi Highlands should they wish to, it has a generally more active PvP population than previous zones however, additonally Stranglethorn Vale is very similar and you can hit up the various trolls ruins and other such areas around there for herbs.

Wetlands is another viable zone for Alliance, it's rather large but contains a generally high amount of herb spots for those willing to travel more off-road than on.

126 - 160 Kingsblood

FAshenvale circuits heading specifically for Kingsblood, Horde can do The Charred Vale as well located in Stonetalon Mountains.

Full circuits of both Hillsbrad Foothills, Wetlands, and running through various parts of The Swamp of Sorrows should you so desire/be of high enough level.

161 - 185 Fadeleaf

This'll be the time to start fully utilizing The Swamp of Sorrows, it not only seems to lack in general player population but also has the highly popular/valuable rogue required item, Fadeleaf.

186 - 205 Khadgar's Whisker

You'll want to start running both full circuits of The Hinterlands, Swamp of Sorrows, and hitting up various high level spots within Arathi Highlands for the maximum herb output.

206 - 230 Firebloom

New areas are both full circuits of The Searing Gorge and The Blasted Lands, both are quite large and rich, another extremely large zone, even in comparison to the other two, is Tanaris. This has so many different "sections" that you can neatly divide it in four and take out each part one at a time.

231 - 250 Sungrass

Full circuits of both Felwood, Feralas, and Azshara as well as should you so wish it The Hinterlands again. Feralas follows a stranger pattern than most due to it's generally annoying terrain, also some of the quests such as Cleansing Felwood can be factored into your herbalism for a greater output of cash/value overtime.

Feralas is generally rich in Sungrass, one circuit for this specifically is The Ruins of Ravenwind at the north west and runs down south into The High Wilderness, the other hits up the Grimtotem Compound, Woodpaw Hills, and pretty much all zones nearby Camp Mojache.

251 - 270 Collecting Gromsblood

Still running full circles/circuits of Felwood, you should be used to it by now. Another place is Mannoroc Coven in Desolace for Gromsblood, Blasted Lands is as good as ever, and finally the Demon Fall Canyon in Ashenvale for more Gromsblood.

271 - 285 Collecting Dreamfoil

Now we start running both Un'Goro and more heavly into Azshara, The Forlorn Ridge down to the Ravencrest Monument is a good run for Azshara as well as The Ruins of Eldareth, heading north from there to the Jagged Reaches and back in a loop.

285 - 300

Finally we head on to both Eastern and Western Plaguelands as well as more Felwood fun, as long as you don't see to many other players you can also hit up Winterspring for Icecaps and sell those to get a bit more cash in the long run.

300-330 - Felwood

Now that you've hit 300 you will need to hit the Outlands for your Master training. Bothe Honor Hold and Thrallmar have Master Herbalism training available. The you can either run off to Outland should you desire a change of scenery or repeat Felwood, farming the heck out of it for whipper roots, etc. This time start at the alliance outpost up north and simply head south all the way to the bottom before returning.

Almost everything you encounter should at the very least be green, alot of them such as Dreamfoil, Plaguebloom, etc. continue giving skill gain until 330 or so whilst the more mass produced/spawned types like Sungrass, Arthas's Tears, and so on also rarely give a skill gain or two.

330 - 350+ - Zangarmarsh

Finally we hit up Outland, previously it might not have been worth it due to the large playerbase, but now Zangamarsh is simply packed to the brim with herbs, it's hard to even try avoiding it. Generally I'll run circuits around the corner areas before slowly circling in towards the center, reverse this process to complete the circuit, also should you run into a bit of opposition try going up north into the Blades Edge Mountains and check that out as well.

350+ You can pretty much go where you will, I expect you possess enough in the way of skills, personally not character wise, to pick and choose where and what to grab for these last skill levels.

Herbalism for Inscription
The herbs needed for Inscription are divided into tiers. Unlike Alchemy, which requires specific herbs for any given potion, Inscription allows the scribe to use any herb from the appropriate tier. Here are the herbs you will want to focus on:

Here are the tiers and their required skills:

Silverleaf (1,) Peacebloom (1,) Earthroot (15)
Mageroyal (50,) Briarthorn 70,) Stranglekelp (85 and a Water Breathing potion,) Buiseweed (100.) Swiftthistle drops with the other herbs.
Wild Steelbloom (115,) Gravemoss (120,) Kingsblood (125,) and Liferoot (150.)
Fadeleaf (160,) Goldthorn (170,) Khadgar’s whisker (185,) and maybe Wintersbite at 195.
Firebloom (205,) Purple Lotus (210,) Arthas’ tears (220,) Gromsblood (250,) Blindweed (235,) Ghost mushroom (245,) Sungrass (270)
Golden Samsan (260,) Dreamfoil (270,) Mountain silversage (280,) Plaguebloom (285,) Icecap (290,)
Any herb found only in Outland, such as Felweed, Ragveil, etc.
Any herb found only in Northrend, such as Goldclover and Tiger Lilly
This allows the herbalist/inscriber to gather any herb from a tier. If one is hard to find, gather the other.

Wrath of the Lich King - Herbalism 350 to 450:
350 - 450

Once you arrive in Northrend do circuits around the starting areas for Goldclover and around the hot springs in Borean Tundra for Fireleaf. (Fireleaf drops leaves and seeds which provide interesting buffs.)

Once your skill hits 400 you can pick Tiger Lily around the edges of lakes and streams. With half an effort your skill will be 450 before you hit the higher level areas for Talandra's Rose, Frozen Herbs, Icethorn, Lichbloom, etc.