Demystifying the pruning of roses

From University of Illinois Extension Garden packet

URBANA, Ill.—It’s time for another rite of spring, the task of pruning roses, said a University of Illinois Extension horticulture educator.

“Pruning roses can sometimes be a very confusing task, especially when you have several different types of roses in the garden such as hybrid teas, old garden roses, shrub roses, and climbers,” said Greg Stack. “With this confusion comes doubt, and doubt sometimes leads to improper pruning or not pruning at all. The type of rose you have and the time of year it blooms will influence the type and amount of pruning needed. General pruning practices can apply to all types of roses, but there are differences between classes.”

The amount of pruning between species and hybrid teas is vast, with the species types needing less severe annual pruning and the hybrid teas needing the most severe pruning for optimum flowering.

“Proper pruning involves several principles that are common to all classes of roses: remove dead, damaged, and diseased canes; increase the air circulation within the plant; keep the shrub from becoming a tangled mess; shape the plant; and encourage the growth of flowering stems,” he said.

“Most pruning should be done in the spring,” he added. “Wait until the weather has stabilized a bit, and temperatures are not going to fluctuate too dramatically. A good guide might be when the forsythias start to bloom.”

The pruning fundamentals that apply to all classes of roses include: use clean, sharp tools; cut at a 45-degree angle above an outward-facing bud; remove all dead winter-injured canes that can be identified as shriveled, dark brown or black; after making cuts, seal the ends of the canes with something such as white glue or pruning paint as this helps to prevent entry of cane borers; remove thin, weak canes that are smaller than pencil size in diameter.

“After basic pruning tasks have been accomplished, you can focus on some specific pruning practices that apply to specific classes of roses,” said Stack.

Roses such as hybrid teas, grandifloras, floribundas, and miniatures producing the best flowers on new or current season canes will require the most severe annual pruning. This usually means removing about one-half to two-thirds of the plant’s height and reducing the number of canes.

Remove all dead canes resulting from winter injury. Then, remove the thin, weak canes, leaving about three to five stout canes. These canes are then cut back to about 4 to 6 inches, leaving about three to five outward-facing buds.

“Modern shrub roses are very popular, and many gardeners are including them in their plantings,” he said. “This class of rose bears flowers on mature canes that are not old and woody. If severe pruning were done to these roses, it would result in reduced flower production.

“Generally, these roses don’t need much pruning the first two to three seasons in the garden other than perhaps reducing the height a bit. In this case, cut the canes back by about one-half,” he added.

Old garden roses are often great additions to the garden because they combine a very classic rose flower shape with fragrance that is very hard to match in any other class of rose. These roses are often pruned much the way you would prune modern shrub roses.

“However, if you have once-blooming old garden roses such as Gallica, Centifolia, Alba, Moss Rose or Damask, remember that these roses bloom on old canes produced the season before,” he said. “The majority of pruning is done right after flowering and not in the spring. Heavy spring pruning would remove the flowering canes and result in little or no flowers that season.”

Climbers and ramblers may need several seasons in the garden before a lot of pruning is needed. In most cases, pruning is limited to removing winter-damaged canes. Pruning is similar for both of these types of roses.

“The difference is in the timing,” Stack explained. “For once-blooming ramblers, pruning is done right after flowering.

“Climbers tend to be repeat bloomers, so they are pruned in early spring,” he added. “Reducing the side shoots or lateral canes to about 3 to 6 inches helps to stimulate flowering. Also, training the canes to a more horizontal position encourages the growth of side shoots that are bloom-producing shoots.”

The one frustrating consequence of including climbers in the landscape is that many are not very good at going through the winter without a lot of cane damage, he added. This damage needs to be cut back, and you often lose a lot of the plant that you worked so hard to grow and cover a trellis or arbor. To minimize or almost eliminate this problem, you might consider growing some very hardy climbing roses that will result in very little cane damage.

“Pruning roses doesn’t have to be a big, mysterious garden chore,” he said. “With a little understanding of some basic principles and an understanding of the slight differences between some classes, your rose garden should be the best ever. So go forth and prune.”

From the April 28-May 4, 2010 issue

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