Plants that flower in early to mid spring will not set flower buds for next year until later in summer. That makes now an excellent time to prune spring flowering plants to ensure maximum bloom next year.
On flowering trees such as dogwood, redbud and crabapple, crossing and rubbing branches should be removed. If the crown is very dense, it should be thinned to allow light and air to penetrate inside the canopy. On flowering shrubs, reduce the height and spread of the plant as needed to accommodate the space that is available. Thinning to improve light and air penetration may also be needed. On species such as lilac and forsythia, older stems should be periodically removed to rejuvenate the shrub.
As with all plants, light pruning can be done anytime. Removal of dead branches should also be performed routinely as needed.