The majority of trees and shrubs can safely be pruned during their dormant period between late fall and early spring. Pruning after new growth emerges cuts off the new growth hormones, which can limit the growth and bloom potential for the entire year. Also, pruning in mid to late summer can seriously damage many plants due to the added stress that the summer heat exerts on a plant.
Popular shrubs to prune after flowering (typically late May/June)
- Forsythia, Pieris, Bigleaf Hydrangea, Quince, Oakleaf Hydrangea
- Spring flowering Spirea, Lilacs, spring flowering Viburnum, Mock orange, Weigela
Most evergreens prefer being pruned in early spring before new growth. If pruned in the fall, they must be pruned in time for the new growth to harden off before winter. Pruning while it's still hot can also severely stress the plant.
- Arborvitae – Light shearing in early spring is acceptable. Touch up again in early summer.
- Broadleaf Evergreen (hollies, inkberries, etc.) – Selectively prune to keep shape. Best if not sheared.
- Boxwood – Keep small for the first few years to increase branch density. Selective pruning is best. If you must shear, it is best to shear in spring and early summer.
- Juniper – Selective pruning is best. Light shearing is acceptable. It is unlikely that new growth will emerge on interior wood.
- Pine – Prune by removing 2/3 of new spring candle growth. New growth will not emerge on interior wood.
- Spruce – Do not shear. Selective pruning only in early spring before new growth.
- Yew – Light to moderate shearing in early spring is acceptable. Touch up again in early summer. New growth can emerge on old wood, but complete rejuvenation of mature shrub is not recommended.
- Remove all spent vegetation in late fall.
- Shear back to a few inches when dormant. Can either be sheared in late fall or early spring. For added landscape interest, keep the dormant foliage through the winter. Must shear before spring growth emerges to prevent squared off tips through the year.