Next, why don't we put them to work on kudzu?

DEA Says 98% of Eradicated Pot is Ditchweed - TalkLeft: The Politics of Crime:

According to the data, available online here, of the estimated 223 million marijuana plants destroyed by law enforcement in 2005, approximately 219 million were classified as "ditchweed," a term the agency uses to define "wild, scattered marijuana plants [with] no evidence of planting, fertilizing, or tending." Unlike cultivated marijuana, feral hemp contains virtually no detectable levels of THC, the psychoactive component in cannabis, and does not contribute to the black market marijuana trade.