ENH1138, a 6-page illustrated fact sheet by Gary W. Knox and Edward F. Gilman, addresses this controversial aspect of crapemyrtle maintenance, providing recommendations based on UF/IFAS research clarifying the effects of various crapemyrtle pruning practices. Includes references. Published by the UF Department of Environmental Horticulture, September 2009.
http://edis.ifas.ufl.edu/ep399