When to Trim Evergreen Shrubs
Gardeners often prune evergreen shrubs to reduce their size, maintain their shape, remove damaged areas or cut off diseased portions. The time to prune depends on the type of evergreen shrub growing in your yard. Broad-leafed evergreens typically do best when pruned right after blossoming. Wait until spring, however, to prune shrubs with needles and narrow leaves.
Two types of evergreen shrubs exist: Broad-leaved evergreens and narrow or needle-leaved evergreens. Correctly identify the type of shrub growing in the yard to help determine when to prune. Broad-leaved evergreens include azaleas (Rhododendron spp.), which are generally hardy in U.S. Department of Agriculture plant hardiness zones 4 to 8 and sometimes hardy in warmer and cooler zones, depending on the cultivar. Types of narrow or needle-leaved evergreen consist of junipers (Juniperus spp.), which grow best in USDA zones 4 to 9.
Broad-Leaved Evergreen Shrubs
Prune broad leaved-evergreen shrubs as soon as they finish blossoming or before July. Flowers set for the next year in the summer. If you prune after the shrubs have set their flowers, you will see bare spots where flowers are not produced. Shrubs that need complete rejuvenation can be cut down to the ground in the early spring, because it will take a year for the plant to grow and recover from the pruning. You know your broad leaved-evergreen needs to be rejuvenated when it has grown too large for its location or produces leggy growth.
Narrow or Needle-Leaved Evergreens
For narrow or needle-leaved evergreens, prune in the early spring. Prune pine (Pinus spp.) shrubs, hardy in USDA zones 3 to 7, depending on the species, before new growth called candles appear after winter. It is essential to monitor the plant for new growth soon after the last frost for your region. Don't cut too deeply into the shrubbery of needle-leaved evergreens, because you will wind up with bare areas in the shrub.
Do not prune shrubs in the late fall regardless of whether they have broad or narrow leaves. Fall pruning encourages new growth that can become damaged in the winter. Freezing temperatures and snow may cause the new growth to die off, and in the spring you may have either browning of foliage or defoliated shrubs.
- Texas A&M University Extension: Follow Proper Pruning Techniques
- Terry L. Ettinger Horticulture Consulting Services: Question of the Week - How to Prune Evergreen Shrubs
- Missouri Botanical Garden: Rhododendron "Boudoir"
- Missouri Botanical Garden: Juniperus Chinensis
- Missouri Botanical Garden: Pinus Densiflora "Low Glow"