The glossy booklet entitled A Guide to Invasive Plants in Massachusetts would probably seem unremarkable to most ecologists. Its cover shows a meadow invaded by waves of purple loosestrife, and the inside pages identify more than six dozen other plants as invaders of natural areas in Massachusetts. The booklet, produced by botanists at the state Natural Heritage and Endangered Species Program, is identical in concept to numerous other invasive plant lists compiled and published by government agencies, exotic plant pest councils, and managers of conservation lands across the United States.