With Washington state about to embark on a first-of-its-kind legal market for recreational marijuana, the budding ranks of new cannabis growers face a quandary over what to do with the excess stems, roots and leaves from their plants. Well farmer Susannah Gross is part of a group experimenting with a solution that seems to make the most of marijuana's appetite-enhancing properties - turning weed waste into pig food. Four pigs whose feed was supplemented with potent plant leavings during the last four months of their lives ended up 20 to 30 pounds heavier than the half-dozen other pigs from the same litter when they were all sent to slaughter in March. Matt McAlman, the medical marijuana grower who provided the pot leavings for Gross' pigs, says he hopes the idea expands with the likely impending expansion of Washington state's marijuana industry. "We can have pot chickens, pot pigs, grass-fed beef," he said.