Cinderbloom

Stays green all the way until 525. I don't recommend it though. At about skill level 500, skill gains from this herb, Stormvine, and Azshara's Veil slow down dramatically. I would often pick 5-15 herbs per skill point.

At level 80, I was getting 2200 experience per herb picked. Even at max herbalism skill, you can still get experience from picking herbs.

It takes 1686300 experience to level from 80 to 81. Thus, you would have to pick about 767 herbs (1686300 / 2200) if you wanted to level solely from herbalism.

If we assume that the experience gain from picking herbs scales with level, then each herb picked is equivalent to about 0.13% of a level. (2200 / 1686300)

Sure, that's a very boring way to level, but if you do it while auction house prices are high, you can level up, max your herbalism, make a fortune off of selling herbs in the auction house, and make a decent amount of money from doing all of the quests you missed (since you make more gold per quest at max level). The only thing you lose in the bargain is your sanity.

A good place to farm these are the Obsidian Forest in Twilight Highlands, there're only Cinderbloom there, pretty small area with quite a lot of herbs and every herbfarmer in Twilight Highlands are farming Twilight Jasmine so you might not get that much competition.

Cinderbloom is in every new cataclysm zone except Vashj'ir. It's even in Tol Borad. There is so much of it that it's value is nothing compared to the many other herbs. Heartblossom and Twilight jasmine are both valuable and zone specific. They both are neighbors of Cinderbloom. This frustrates me.

<Herb Finder pings on mini-map radar>
Me: "Omg rare herb! Use a masterball!"
Me: <Flies down to pick up the herb with an ear-to-ear smile>
Me: <Looks at herb>
Me: ".... CINDERBLOOM"