Encroachment of woody species reduces the productivity of sphagnum moss (Sphagnum sp.) in acid bogs. Leatherleaf (Chamaedaphne calyculata (L.) Moench) and black chokeberry (Aronia melanocarpa (Michx.) Willd.) were major species of concern to moss harvesters. Black chokeberry was controlled by spray applications in spring of 4-amino-3,5,6-trichloropicolinic acid (picloram) at 1 lb/A. Leatherleaf was controlled by either fall or spring applications of picloram at 1 lb/A. No control was obtained with eight other herbicides tested. Sphagnum moss carried phytotoxic residues three growing seasons after picloram application.