This quest can be acquired from Brother Nicodemus at the Sasau monastery. Ask him if he is willing to teach you anything and he will request that you weed his garden of Thistles, Nettles and Dandelions.
Go to the garden patch north of his workshop and weed it of all three. Be sure not to take any Eyebright or Mint. Once you are sure that everything has been weeded appropriately, go back and speak with Brother Nicodemus. He will want to inspect the work himself. Follow him to the garden patch and speak with him once he has inspected it. If you have done a decent job he will reward you with Groschen.