They flower on old wood. Prune straight after flowering.

Hi, Prunus triloba and P glandulosa, are usually grown as wall trained shrubs, or in a shrub border, and as Steragram says, should be pruned after flowering, most Prunus are in pruning group 1, but P triloba are in pruning group 5, or group 13, if wall trained, if silver leaf is a problem in your area, prune in mid summer, Derek.