The general principle of rose pruning is that cutting off old wood produces new wood and more blooms each year.
The severity of pruning differs. Prune more severely for larger (but fewer) flowers, for a smaller bush, or if a plant is weak. Heavier pruning leaves fewer buds to share the food stored in the dormant roots, so each bud will grow more vigorously. The degrees of pruning are defined according to the number and length of canes that are left:
Severe pruning leaves only 3 or 4 canes, each 6 to 12 inches long. Moderate pruning leaves 5 to 12 canes, each 18 to 24 inches long. Light pruning cuts back about a third of the plant.
Severe pruning is the prevalent practice in harsh climates, where the exposed bud union must also be protected from frost, usually with a protective mulch. Prune moderately throughout the flowering season to restrain the plant, disbud to get larger but fewer flowers if desired, and remove spent flowers.
TYPES OF ROSES
Roses are categorized according to whether they bloom on wood produced in the current or previous year. Most modern continuous-flowering roses bloom on the current season’s wood, but many older roses and species roses bloom on the previous year’s wood. Roses that bloom on the previous year’s wood should be pruned after flowering, before new shoots emerge. Most of these roses produce flowers in spring and are not repeat bloomers.
Most roses in modern gardens are continuous-blooming varieties that produce flowers on the current season’s growth. This group includes most of the modern hybrid tea, floribunda, and grandiflora roses. They should be pruned when the plant is dormant but when the buds have begun to swell. The time will be in January in the mildest climates and after the last frost in severe climates.
Here are some guidelines for pruning the most prevalent type of roses to produce good flowering:
1. Remove dead or frost-damaged wood down to the nearest healthy dormant bud. Cut until you reach healthy wood, which is cream colored
2. Cut out any weak, spindly, or deformed twiggy growth. Remove canes pointing in toward the center, to open up the plant. Where branches cross, remove the weaker one. Remove any suckers that originate from below the bud union by cutting or breaking them flush with the stem. Remove old canes that produce much twiggy growth (old wood has darker bark than new wood).
3. For most plants, thin to 3 to 5 canes that are 8 to 24 inches long. Cut the excess canes back to the bud union. Make cuts to outward facing buds to create a pleasing vase shape.
4. In general, the more vigorous the plant, the less you prune. Vigorous roses have new canes 3/4 inch in diameter. You can leave 6 canes on strong plants. Cut canes that you leave back by about a third if the rose is vigorous and back 2 or 3 buds if it is weak.
5. If the rose is new or weak, remove the flower buds as they form the first year to build strength of the bush. When you remove roses for cut flowers, leave at least 2 sets of leaves that have 5 leaflets each. This allows new flowers to be produced on long, vigorous stems.
CLIMBING ROSES Most climbing roses flower on year-old wood. Don’t prune them for 2 to 3 years, except to remove dead wood. They need this amount of time to establish mature canes for flowering. Long canes grow from the bud union. Don’t tip these canes. The long canes don’t flower, but flowers appear the next year on the laterals of these canes. Prune back to 3 to 5 young canes. Prune the laterals on these canes back 2 or 3 buds. Pruning climbers with pliant canes is easiest if you unite the rose from its trellis or other support and lay it on the ground. Use soft ties to refasten the climber to its frame. Some varieties of climbing roses are unusual in that they flower on both old and new wood.
SPECIALLY SHAPED ROSES Standards, or tree roses, are bush-type roses that have been grafted for effect onto trunks that are 3 or 4 feet tall. To keep the trunk unbranched, rub off sprouting buds that develop along it. Prune to keep the top symmetrical and to remove any dead, crossing, or diseased canes. Remove any suckers that emerge from the root stock or along the trunk. Hedge and border roses are vigorous, bushy plants.