A new cultivar of bee balm, Monarda didyma `AChall`, that is characterized by its deep red-purple blossoms that are present abundantly in June through August. The new variety is mid sized in height with an upright oval plant habit, is hardy in U.S.D.A. Zones 3 to 8, and exhibits dark green semi-glossy foliage that has shown resistant to powdery mildew.