In her attempt to prevent the Oz foursome from reaching the Emerald City, it is the Wicked Witch who is behind the fields of poppies that lie before them. The idea of the opium-filled flowers was part of Baum's original storyline and had nothing to do with the Wicked Witch. The snowstorm summoned by Glinda the Good Witch to destroy the poppies and save the characters in the end, originated with the 1902 stage musical, a scene that signified the end of the first act. TM & (c) Turner Entertainment
The simplest way to clean up an oil or acrylic painting on canvas is to use a white cotton cloth soaked in a gentle soapy water; olive oil–based soap works wonders. You’ll be surprised to see how much grime comes off. Be gentle with paintings with thick impasto, as you do not want to break hardened paint. You might want to use Q-tips and work gently in crevasses.