At the Chicago Botanic Gardens (which are actually in Glencoe, IL) www.chicagobotanic.org/
According to the cover story in the February 2009 issue of Uncut, Johnny Cash never stopped being addicted to amphetamines, and other pills. The story had always been that when Cash married June Carter, he cleaned up his ways, became a religious man, yadda yadda.
The entire article doesn’t seem to be online, but here’s Nick Cave on Johnny Cash