Maybe the trees are "pining" for their freedom.
Of course, the problem with writing comic strips with crazy fictional characters is that real-life people will always manage to out-crazy you. There is probaby someone out there right now actually doing this exact thing.
As my awesome reader Sam pointed out, in Strip 256 Drew is taking up a cause already championed by Lisa Simpson. I'm reminded of the South Park episode where every mischevous plot the characters concoct has to be abandoned because "The Simpsons already did it."
And equally awesome reader Stephan shared this video on the vegetable rights movement