Goutweed

Goutweed is a rare herb that is not used in Herblore per se, but rather traded to Sanfew in Taverly for random herbs at a 1:1 ratio.

Goutweed is obtained in only two ways:
 * By sneaking past Ogre guards during (and after) the Edgar's Ruse quest.
 * By digging up Gout tubers during the Tai Bwo Wannai Cleanup minigame and planting them as herb seeds.