Pruning Shrubs and Evergreens

adapted from "Management of the Landscape around Residential Property", Basic Horticultural Concepts and Practices, Ronald C. Smith, Ph.D., Ohio State University

The guidelines outlined here are for plant materials which need rejuvenation as well as an occasional trim.

Pruning should be done when:

• A bush presents a visual or physical hazard to passersby

• There is evidence of disease or an insect population weakening a particular plant

• There are any damaged or broken limbs or branches

• To improve chances of survival during transplanting

• To alter the habit of growth of a particular plant

• Improvement in flowering and fruiting are desired

There are times when pruning is more ideal for plants than at other times, but pruning when necessary should not wait for a particular season.

Flowering Shrubs

Pruning of flowering shrubs should be correlated with the blossoming habits of the species. Generally, the best time to prune flowering shrubs is right after they have finished flowering, so that next season's flower buds will not be removed. (Those that bloom early in the spring should not be pruned until after the flowers have dropped; species that bloom later in the season may be pruned during the fall or winter.)

If just simple shaping is needed, cut back to a side branch or bud, preferably one on the outside. If major renovation is needed, cut the old thick canes down as close to the base of the shrub as possible. Plants like the common lilac (which may be grafted), forsythia and mock orange will send up new sucker growth from the base which can then be shaped by hand pruners or by pinching. Never wait until the end of the summer to prune plants like lilac or azaleas as doing so will only remove the flower buds that have formed for next spring.

Hedges

Most hedge material can be pruned at the convenience of the homeowner, as most are not grown for flowering. Therefore, limb removal will not destroy any outstanding aesthetic features. Hedges should be pruned so that their base is wider than the top. Hedges like privet and buckthorn can be cut to size in the later winter months, and the resulting new growth shaped to the desire of the homeowner. If the privet hedge on the property is bare and open at the base, cut the entire hedge back to the ground in late winter and shape the new growth to be wider at the base. With Winged Euonymus or Viburnum as a hedge, the cutting back should take place over a period of two years. Remove about half the branches to the ground the first year, then the balance of the old branches the second year.

Roses: Hybrid Tea, Floribunda, and Grandiflora

Better flowering results can be obtained with tea, floribunda and grandiflora roses when they are cut back in the spring rather than the fall. May times the rose canes are killed back to the mulch line in the winter, so cutting should be in wood that is alive and healthy.

When removing blooms, cut, if possible, back to a five-leaflet leaf about a quarter of an inch above the node. Only the sharpest pruner should be used on rose canes as they are subject to easy bruising.

If bare root roses are purchased in the spring, the shoots and roots should be cut back about a quarter to a third of their overall length.

Evergreens

Needle-leaf evergreens: The pines are genera which produce candle-like growth in the spring. This new growth may be cut back at about half their length before it completely hardens. Shear young Mugho and Swiss Stone pines for a few years, then selectively pinch back new growth to keep the plants compact but not symmetrical.

Taxus species: Taxus may be pruned at any time, but best results are obtained when they are pruned in the early spring before new growth emerges. The ensuing new growth will hide the pruning cuts. Taxus are commonly topiaried, indicating that severe pruning can be done if necessary.

Scale-leaf evergreens: The arborvitaes and chamaecyparis comprise the major genera which are in this classification. Both can be pruned any time during the summer, but care should be taken to be sure that where cuts are made, some foliage remains. Never cut back to bare wood, since the result will be unsightly.

Broad-leafed evergreens: Rhododendrons, azaleas and hollies pose no problems in pruning. Just remember that the rhododendrons and azaleas are noted for their outstanding flowers which form during the summer months for the following season's show. If pruning is carried out too late in the summer, it will remove some flower buds. Therefore, pruning these specimens as the flowers fade is the best policy.

If any of these plants need rejuvenation pruning, do so by cutting the oldest branches back in the late winter to nodes. New growth will emerge at the base from latent buds. Hand pinching of this soft growth will encourage further bud break and develop a more compact bush.