The frozen herbs in Dragonblight have gotten my herbing to 445. They're still yellow, so I'll be able to cap herbing with them. I'm only level 72, so it was a lot easier than I thought it would be to max.
Looking around, I see some conflicting information. Here's what I can find so far:
Goldclover -- orange 350 -- (Borean Tundra, Howling Fjord, Dragonblight)
Firethorn -- orange 360 -- (Borean Tundra)
Talandra's Rose -- orange 385 -- (Zul'Drak)
Tiger Lily -- orange 400 -- (Borean Tundra, Grizzly Hills, Howling Fjord, Sholazar Basin)
Frozen Herb -- orange 415 -- (Dragonblight, Zul'Drak)
Lichbloom -- orange 425 -- (Storm Peaks, Icecrown)
Adder's Tongue -- orange 430 -- (Sholazar Basin)
Icethorn -- orange 435 -- (Storm Peaks, Icecrown)
Frost Lotus -- orange 450 -- (Wintergrasp)
Looks like the yellow and green numbers aren't well documented at this point. Wowwiki has a couple, but they don't make sense, with a yellow number lower than the orange number.
My path to 445 so far has been Gold Glover and Firethorn, then Tiger Lily, then Frozen Herb.
EDIT: I'm up to 450 now, capped it off still in Dragonblight using the Frozen Herbs.
Edited, Nov 25th 2008 8:46am by azwing