Maybe burning it wasn't the brightest idea...

Taliban Fighters Hide Inside Giant Marijuana Fields

Canadian troops fighting Taliban militants in Afghanistan have stumbled across an unexpected and potent enemy -- almost impenetrable forests of 10-feet-high marijuana plants.
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"We tried burning them with white phosphorous -- it didn't work. We tried burning them with diesel -- it didn't work. The plants are so full of water right now ... that we simply couldn't burn them," he said.

Even successful incineration had its drawbacks.

"A couple of brown plants on the edges of some of those (forests) did catch on fire. But a section of soldiers that was downwind from that had some ill effects and decided that was probably not the right course of action," Hillier said dryly.