The technique of pruning depends on the type of rose and the landscape purpose for which it was planted. Pruning can range from mild removal of unwanted buds to severe excising of canes. When a plant is properly primed, growth at the buds closest to the cut will be stimulated and new flowering stems will be produced.
Steps for Pruning All Roses
Pruning can be a scratchy job, so wear gloves and a long-sleeved shirt or jacket to protect your skin against thorns. Some kinds of fabric, such as the nylon used in windbreakers, catch easily on thorns and can tear.
The first step in pruning any type of rose is to remove any dead, damaged, diseased, or weak and thin canes, cutting them off flush with the bud union or, in the case of own-root plants, flush with the crown.
Any canes that are broken or wounded, or that have cankers (dark, sunken lesions caused by a fungus), should be pruned below the injury, at the highest point where the pith (the central portion of the cane) is healthy and white. Make the cut 1/4 inch above a growth bud. If the injury extends below that point, cut to a lower growth bud.
Next, remove canes that are growing into the center of the plant, or those that cross each other. Canes that grow inward keep light and air from the center of the plant and will eventually cross, chafing one another. These abrasions can become entry points for insects and diseases. Using shears, cut these canes down to their origin, whether that be another cane, the bud union, or the crown. It is important to keep the center of the plant open to let in sunshine and allow air to circulate freely.
Always prune to an outward-facing bud so that canes do not grow into the center of the plant. Prune close enough to the bud that no stub remains to die off and harbor insects or diseases, but far enough away that the bud will not die. A good distance is about 1/4 inch above the growth bud. it is also important to cut at the proper angle, so that water runoff won’t drip on the bud or collect in the cut and retard healing. The ideal angle is 45 degrees, slanted parallel to the direction of bud growth.
Pruning Hybrid Tea, Floribunda, and Grandiflora Roses
On hybrid teas, floribundas, and grandifloras, once you have pruned the diseased, damaged, and weak canes, select three or four of the newest and healthiest remaining canes and cut off the rest flush with the bud union, using pruning shears or a saw if necessary. Next, prune the remaining canes of hybrid teas and floribundas to a height of 12 to 18 inches above the bud union, and those of grandifloras a few inches higher. Floribundas used as hedges can have five to six canes left on each plant, and can be pruned to 24 inches high so that they will grow denser and taller and produce more flowers.
Pruning Shrub and Old Garden Roses
Shrub roses and old garden roses, including species roses, do not require severe pruning unless they are overgrown. In early spring, cut out weak, damaged, or dead wood, and prune only to shape the plant or control its size. Leave the plants as large and as natural looking as space permits. Perform heavy pruning either in early spring or after flowering, depending on the type of plant.
Many old garden roses — albas, centifolias, and moss roses in particular — have long, supple canes that can be bent over and pinned to the ground. This practice makes these plants easier to control and gives them a bushier appearance. It also encourages the formation of new basal breaks (new canes that grow from the base of the plant), which keeps the plants constantly rejuvenated. The canes often root at the point where they were pegged to the ground, and new plants that form can be left in place or transplanted.
Pruning Polyantha Roses
Polyanthas are hardy plants that, like many old garden and shrub roses, seldom suffer winterkill. They are therefore pruned more like old garden and species roses than like hybrid teas, floribundas, and grandifloras. if they are not overgrown, trim only to remove old, damaged, or diseased canes. if they are overgrown, prune them in early spring, to about half their former height, and remove the oldest canes. Leave them on the bushy side, as they are grown primarily for landscape effect.
Pruning Climbing Roses
Because climbers bloom solely on old wood, they are pruned somewhat differently than bush roses. In early spring, while the plants are still dormant or have just started to grow, any dead or damaged canes can be removed, as can those that are too long or misshapen. However, leave all other pruning until after the plants first flower, so that you do not remove any flower buds. This is especially important with climbers that bloom only once a year. Those that repeat their bloom may actually be encouraged to have a heavier second bloom if they are properly pruned after the first bloom.
The oldest canes should be removed to the bud union to leave room for new growth. Thin out dense growth as well at this time. Removing flowers as soon as they fade encourages some climbers that would not otherwise flower again to repeat their bloom during the summer.
Because climbers flower only on lateral branches that grow from the main canes, they will bloom more heavily if they are trained along a fence or a trellis, and if the ends of the canes are directed to grow down toward the ground. This forces the plants to produce more laterals. As new canes of climbers grow, they must be trained into position and tied to their supports with cord, string, or twist-ties.
Pruning Miniature Roses
Prune miniatures to about half their ultimate summer height. Up to six strong new canes can be left on the plants after pruning; the more canes you leave, the fuller the plants will be.
Pruning Tree Roses
Tree roses are pruned like modern bush roses, but to be most attractive they must be as symmetrical and pleasingly balanced as possible. Prune canes to about 12 inches beyond the bud union at the top of the trunk and leave them as evenly spaced around the plant as possible. Leaving four to six canes on each tree rose will produce a full, attractive plant.
Pruning Roses in Containers
Roses grown in decorative containers should be pruned so that they will be in proportion to the size of the container when they are in full bloom; this may mean shorter or higher pruning than is normally recommended. Since these are usually showcase plants, take care to prune them so that they are as symmetrical and pleasingly balanced as possible.
New growth starts at the growing point immediately below a pruning cut. This is especially important to bear in mind when pruning back large, overgrown plants. If your ultimate goal is a plant 6 feet high or a climber trained to cover a section of fence 8 feet long, you must prune the plants shorter than the desired size in order to allow for new growth. For example, if your goal is a 6-foot-tall shrub rose, you should prune it to about 4 feet tall. Different plants have different growth rates, so gauge your pruning according to the past behavior of the plant.
In warm climates with long growing seasons, where rose plants grow quite large, pruning to the recommended height is not desirable since it will remove too much of the plant. Instead, prune away about one half to two thirds of the plant each winter or early spring by removing the older canes and shortening the remaining canes.
In cold climates where there is a great deal of winter damage, pruning heights may be determined for you by the amount of winterkill. Prune canes down to where there is no more winter damage, even if it is almost to the ground.
The higher a plant is pruned, the earlier it will flower — but don’t jeopardize the health and vigor of the plant by pruning too high in pursuit of a few days’ earlier bloom. On the other hand, there is little advantage to pruning your roses lower than the heights prescribed above; unlike disbudding, it will probably not make the plants produce larger flowers.
Pruning and Diseases
Although black spot and other fungal diseases manifest themselves on leaves, their spores overwinter on rose canes. If these diseases plagued your roses during the previous summer, you should prune them lower than recommended, as you will cut away and discard much of the source of the problem. Although you won’t be able to see the spores on the canes, you can be assured that cutting off a few extra inches during spring pruning will reduce the number of spores. Never leave rose prunings on the ground. They not only look unsightly but can harbor diseases and pests that may potentially reinfect the plant or spread to others.
Pruning cuts more than 1/4 inch in diameter can be sealed with pruning compound, orange shellac, or grafting wax (available at garden centers or hardware stores) if boring insects are a problem in your area. Pruning compound and orange shellac are the easiest to use because they can be painted on. Otherwise, sealing is not necessary. Some types of white glue, which is sometimes used as a sealant, are water soluble and will wash away with the first rain or watering; they should therefore not be used.
Pruning Young Plants
Do not be too harsh when pruning young plants. Until plants are well established and have been growing robustly for two or three years, remove only weak, damaged, or dead wood, and shape and shorten the plants as recommended above without cutting away any of the older canes. In following years, old canes can be removed as new ones develop.
Roots can be pruned as well. When you plant or transplant a rosebush, prune off any broken or damaged roots. You should remove about one third off the tops of the canes to compensate for this root loss. Before transplanting a large rosebush it is a good idea to prune the roots with a spade by digging in a circle around the plant. Do this one to six months before the transplant so that the rootball will be more compact and easier to move.
Several weeks after you have pruned, take a second trip through the garden with your pruning shears. If you pruned early in the year, a late frost may have caused minor dieback on some of the canes. This dieback should be removed. Cankers that were not apparent at pruning time may be visible and should also be pruned away.