The Green March

The Green March is not an official quest, but since it requires the same amount of legwork as any other quest in the game, it will be treated in the same manner as an official but optional quest. It takes place in Chapter V of the game when Geralt finds the druids holed up in a cave in the swamp cemetery.

Walkthrough
In the Druids' cave in the swamp you will find a group of druids, preparing for a so-called "Green March"; a march of protest against logging and the murder of endangered species. For their march, they need gems for an effigy of King Foltest, whom they hold responsible as leader of the kingdom, a banner, of course, and some symbols for the march participants to wave as they go by. They will exchange potions for these items.

Goods for trade
Here is a summary of what will be exchanged for what: