The Trial of the grasses or herbs was an incredibly painful trial which young witcher apprentices were subjected to. It required the consumption of special alchemical ingredients known as "the grasses" and affected the nervous system. Reportedly, only four in ten survived the trial, but those who did gained lightning quick reflexes in return. The trial was performed in the witchers' laboratory at Kaer Morhen.
- In the video game, it is during this trial that Geralt's hair is said to have turned completely white. In the books, however, Geralt's hair turned white as a side effect of some "additional experiments" which were performed on him. However both are true due the fact that the ones experimenting on Geralt modifed his trials.
- "Trial of the Herbs" is the title of a song by Marcin Przybyłowicz included on the Inspired by The Witcher CD.