Cape Town - The last week of July and the first week of August are traditionally regarded as the weeks to prune roses.
Why do we prune roses in late July?
“Remember, pruning is cosmetic. The main aim of pruning roses is to prevent the bushes from degenerating into a tangled mass of weak stems that bear poor quality blooms in summer,” said rose expert Ludwig Taschner.
Pruning concentrates the plant’s energy into producing strong new growth. So we prune roses to keep the plant looking great, influence the shape or size, to encourage new growth and flowers, or to rejuvenate tired plants.
Very old or neglected plants do best with a light pruning.
It is important to use good quality tools, and to clean and sharpen them prior to using. Blunt tools can bruise and tear branches, allowing infection to enter. Use secateurs for small cuts, and a pruning saw for small limbs or shrubs.
Long-handled loppers are useful for out-of-reach or awkward spots. Wear gloves and closed shoes as a sensible precaution against scratches, thorns and possible infection.
How do you prune a rose?
Remove all dead, diseased or damaged parts of the plant, along with any stems that cross. Some rose growers cut back all branches to a metre in height, while others prefer the more conventional method of trimming back, whilst removing old and diseased wood.
Branches that cross or rub against each other should be removed, as should any stems thinner than a pencil in thickness, as these are never going to produce strong growth or flowers. Climbing roses should have branches trained as horizontally as possible to encourage flowering.
Inward growing branches are also removed to allow light and air to reach all parts of the bush.
Cuts should be made smoothly and cleanly at a slant just above an outward facing bud. Cutting too near the bud will damage the growing point, and too far above could result in a place for insects and disease to enter. To avoid tearing bark when pruning large branches, first make a small cut on the underside of the branch, then make the final cut from the top.
There are different thoughts on sealing cuts. Some gardeners believe that painting with a commercial cane sealer reduces the risk of dieback and borer, while others feel that providing cuts have been made cleanly, a healthy plant need not be sealed. Never put diseased or thorny prunings on the compost heap.
A general rule of thumb is to prune miniature and shrub roses to half their present height, and bush roses by about a third, cutting just above an outward living bud – the reddish-purple swelling on the bark.
Most climbing roses bloom on wood that is two years or older, so only unproductive older wood or spindly growth need be removed. Spring-flowering ramblers are treated differently from modern climbers, and pruned directly after flowering.
Never prune rambling roses or heritage roses that only flower once in spring and early summer, and are forming buds now. Never cut back Iceberg roses too drastically.
Spring flowering shrubs:
Not all plants should be pruned at this time. Late winter and spring-flowering shrubs should be left and cut back after flowering.
Never cut back spring-flowering shrubs such as azalea, camellia, deutzia, philadelphus, rhododendron and spireas, or you will be cutting off developing flower buds.
Hydrangeas:
Prune hydrangea stems to half their length in July and you will lose an entire season of flowers.
As the flowers of the common garden hydrangea (Hydrangea macrophylla) are borne in summer on the old wood, a light trim should theoretically be carried out directly after flowering in late February. At this time, remove old canes and dead-head the previous year’s stems which only bore a single flower.
In practice, however, the trimming of hydrangeas can also be done in late winter when the leaves have dropped from the dormant plants. Prune older, heavier stems that are two or more seasons old and carrying several dead flower heads back hard to the base of the plant to stimulate new, vigorous growth the following season.
Kay Montgomery, Weekend Argus