Leafy (deciduous) shrubs can be pruned now in springtime, preferably before they leaf out fully. A little touch-up trimming can be done through the growing season. Evergreens are best pruned in May and June.
But the way shrubs are pruned is very important to their beauty. Shearing shrubs as though one was shearing a sheep results in a very unnatural appearance.
Instead, use a hand-held pruning shears to selectively cut back branches and twigs in slightly varying lengths. This accomplishes the need to trim the shrub, or reduce its height, while maintaining a natural growth habit. Selectively pruning branches in an intentionally random fashion works well, and avoids the sheared ice-cream-cone or basketball look that detracts from most landscapes. Shearing is not the same as pruning.
There is a definite time and place for shearing. Formal hedges in the right location look beautiful when well-manicured and sheared to perfection. And Disneyland wouldn’t be the same without shrubs sheared to look like Mickey Mouse and Donald Duck. Happy Gardening!