Now's here's the funny thing about picking those Firethorns. You have a chance of getting the Fire Leaf or the Fire Seed. Apparently when you pick a Firethorn, you have a much much higher chance of getting the item that you could actually use. So if you are a toon going off of mana, nearly 80-90% of what you pick will be Fire Seed. This was the case for me when I first went to the Geyser Field area, as it was for my herb/alch partner in crime Vel.
I'm trying to pick enough Fire Leaf for both Vel and I to make flasks. I fly around in flight form, swoop down, then shift into kitty form before picking. A little more work, yes, but now I would say 70-75% of my picks are Fire Leaf. So if you are a druid herbalist trying to farm Fire Leaf, switch into kitty or bear form before picking.