WHEN SHOULD YOU PRUNE?
It’s wrong to think that effective pruning can be done at any time. As a general rule of thumb, avoid pruning any flowering shrub in late summer or autumn because this can stimulate tender new growth, which is susceptible to damage by cold temperatures.
SPRING FLOWERING SHRUBS,
such as forsythia, purple sandcherry, flowering almond, lilac and mockorange, bloom on the previous season’s growth, sometimes referred to as “old wood.” In other words, the flowers we see this spring actually developed on the plant late last summer. For maximum flower production next year, prune spring flowering shrubs immediately after blooms fade.
SUMMER AND EARLY AUTUMN FLOWERING SHRUBS,
such as butterfly bush, Peegee hydrangea, roses and rose of Sharon, bloom on the current season’s growth or “new wood,” which means flowers have developed since growth started that spring. These plants should be pruned just as growth starts in early spring before buds form.
Pruning Hydrangea paniculata to an outward-facing bud (reference step 3 on next page).