Ah nature, the bitterest of enemies!
There, I'm back. It appears that marijuana plants absorb a tremendous amount of heat and makes it difficult to detect people and vehicles by thermal signature. This is being used to great effect in some areas by the Taliban. Also, because plants are very green and hold a lot of water, they are difficult to burn, and when the troops did burn some of them, a group of downwind soldiers experience "ill effects and decided that was probably not the right course of action."
I wonder if the Tim Horton's in Kandahar has had a run on double chocolate?