If you intend to prune any shrubs that have already flowered this year, it needs to be done by the fourth of July. This will allow them time to develop flower buds for next year.
Remove spent flowers from perennials (like Iris) to tidy the landscape.
Some perennials will re-bloom if cut back. My Bachelors Button (Centurea), a blue flowering plant, is just finishing now and if I cut it in half, it will look great in another month or so.
Tall fall mum varieties benefit from a light cutting this time of the season. It makes the plant stouter so it will stand strong in the fall and not fall over with the blooms.
Evergreen trees and shrubs can be pruned right now. The trees should have only one leader branch at the top.
Any branches on Hydrangea, or any shrubs, that never leafed out should be clipped off for a cleaner look. They will not grow any more leaves on those stems this year.
