Wild Spineleaf

Wild Spineleaf was a reagent for the Druid spell, Gift of the Wild Rank 4.

Source
Can be bought from various Reagent vendors in the world. It can also be bought from Argent Squire/Argent Gruntling once the Argent Pony Bridle has been acquired. It can also be bought from / when a player has the Traveler's Tundra Mammoth.