Our roses begin the year with a fresh and new start when we prune them and clean up and dispose of all the clippings and old leaves in the garden. Pruning is the best way to revitalize roses since it puts them into dormancy for a well-earned rest, interrupts any ongoing pest and fungal problems and shapes the rosebush to maximize air circulation and resume growth in the early spring on strong, healthy canes.
When we prune properly, we provide a good framework for the rosebush to grow beautiful roses. We do our main pruning in January, but every time we make cuts throughout the year, we should keep the same principles and goals in mind.
Our first step is to examine the rosebush at its base, which is called the bud union on grafted roses. We first remove dead and damaged canes and then turn our attention to the old, gray canes, which are not as productive as new, green canes. If there is a sufficient number of new canes, we can remove the old canes. If we only have old canes, then we take out at least one old cane all the way down flush with the bud union. This will open up space at the bud union for a basal break, the term for the beginning of the growth of a new cane. If there is a good green cane coming out of an old brown cane, our decision to keep it or remove it depends on how many other productive canes we have on the rosebush.
Next, we clean out weak or spindly growth and any crowded and crossing canes, and when we are finished pruning, we strip the rosebush clean of all remaining leaves.
When you prune your roses, make your cuts above a bud eye. A bud eye is a swelling on the cane where a cane or leaf will grow out. There can be many bud eyes on a cane. New growth will grow in the direction of the bud eye you select to make your cut. Make your cuts at a 45-degree angle about 1/4 inch above a leaf with five (not three) leaflets where you notice a strong, outward-growing bud eye. This choice of the outward-growing bud eye will “direct traffic” as it will prompt the new cane to grow in the direction away from the center of the plant.
The importance of this is that we are trying to shape the rosebush with the center open for air circulation. Rose diseases and pests are opportunistic and like to situate in dense clusters of leaves. An open vase-shaped rosebush is your best start to avoid rose pestilence. Aim to leave no more than 1/4 inch above your cut, because anything more than that often leads to dieback in the cane, which can work its way further down the cane once it gets started.
Unlike fruit trees, roses don’t have thick sap that leaks out after a cut, but most rose growers still make their cuts on this 45-degree slant practiced when pruning fruit trees. Whether you cut on a slant or straight across, aim for a clean cut. When you cut a cane, the pith should be creamy white. If you find that it is brown, you should keep pruning further down the cane until you arrive at clean, white pith, otherwise remove the entire cane.
In San Diego, there is no reason to prune the canes down to 12 or 18 inches as practiced in colder climates. The general height guideline here is to remove the top third to one-half of the rosebush, but an important consideration to take into account is the age and growth habit of the rose. Some roses are naturally taller than others, and once you cut out the dead, damaged, crossing canes and twiggy growth, you can stop pruning even if the rose is still 4 or 5 feet tall.
All the canes on the rosebush do not need to be pruned to the same height. Hybrid teas are generally pruned more severely than other varieties. With shrub and floribunda roses, you can leave more canes and stems than you would on a hybrid tea, because you want to encourage a multitude of luxuriant blooms.
The tools needed to prune your roses are sharp bypass pruners, loppers to cut through thicker canes and a pruning saw to enable clean, flush cuts. You should wear a long-sleeve shirt and a good, sturdy pair of gloves. When you are finished, you will need a rake to clean around the base of the roses to remove all leaves and clippings from the garden.
In addition to those tools, an invaluable experience in learning to prune your roses — including climbing roses, which are pruned differently — is to bring your gloves and pruners and attend the annual hands-on pruning workshop presented by consulting rosarians of the San Diego Rose Society in the Balboa Park rose garden. This year, this event is at 9:15 a.m. on Jan. 9.
Perwich is a member of the San Diego Rose Society and a master gardener with UC Cooperative Extension.