Attack Roses While They Sleep

8bd4This theme may be getting a bit redundant about now. There is just so much that needs to be done in the garden through winter for what will bloom in spring and summer. We plant new fruit trees, and prune mature ones. When we finish planting spring bulbs, we can start planting summer bulbs. Berries, rhubarb and grapes all get planted. With all this going on, it is also time to prune roses.

Like so many fruit trees through the past few centuries, modern roses were bred to maximize production. Instead of big and abundant fruit, they produce big and colorful flowers. Such enhanced production is more than overgrown rose plants can sustain. Pruning eliminates superfluous stems to concentrate resources into fewer but more vigorous stems, and flowers of superior quality.

Pruning also eliminates diseased, damaged, dead and dying stems; which are known as the ‘four Ds’. Foliage falls from the stems naturally through winter, but should be raked and disposed of because it can spread disease to new foliage in the spring. (Dormant fungal spores and bacteria overwinter in fallen foliage.) Foliage that clings to stems after pruning should be plucked away.

Pruning should ideally be done by the time buds begin to swell in late winter. Of course this is not as easy as it sounds in the mild local climate. Buds swell early, and may even start to grow before rose flowers from the previous season finish blooming! Modern ‘carpet’ roses and a few other shrubby types barely go dormant, but fortunately, they do not need such meticulous pruning anyway.

Hybrid tea roses need the most severe pruning, which leaves only three to seven canes approximately two feet high. These canes should ideally be unbranched below where they get pruned, and be spaced somewhat evenly around the center. Stout canes that grew last summer from the base of each plant are best. However, canes below graft unions are suckers that need to be removed.

Floribunda roses are pruned similarly, but can retain a few more canes. Some grandiflora roses are allowed to get significantly taller, with new canes on top of canes from the previous year, which may already be on top of canes from another previous year. It may take a while before they develop replacement canes from the base. Climbing roses likewise retain old canes for a few years.

Tree roses should be pruned as if the upper graft union is at ground level, so that canes should be about two feet high above the graft union. (Although, tree rose canes are usually pruned shorter.) Carpet roses and a few bramble types only need to be pruned low, but cane quality is not so important. They are not grafted, so can not develop suckers.

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Prune Now For Roses Later

70524thumb+The main problems with roses locally are not related to climate, soil, insects or disease. Warm and semi-arid climates of California happen to be some of the best places in the World for roses. Sure, many roses have problems with insects such as aphid, and diseases such as powdery mildew, but primarily because such pathogens proliferate among roses that are not pruned properly.

Yes, the main problems with roses are a direct result of improper pruning. Without adequate pruning, roses become overgrown thickets that shelter the pathogens that afflict them, but also lack the vigor to be resistant to damage. Like so many other domesticated plants, they were bred for maximum production of unnaturally big flowers, at the expense of natural resistance to pathogens.

Pruning eliminates superfluous growth and improves air circulation, which interferes with the proliferation of most types of pathogens. Most pathogens overwinter in fallen foliage that should get removed in the process. Pruning also concentrates growth of the next season into fewer new stems, which stimulates vigorous growth that hopefully grows faster than the pathogens that infest it.

Roses should be pruned while dormant in winter, after defoliation, and before buds start to swell at the end of winter. Hybrid tea, floribunda and grandiflora roses should be pruned back to only about three to six canes that grew from the base during the previous year. Older canes should be removed. Remaining canes should be only about two feet tall, and cut just above a healthy bud. Any growth below the graft union (where the basal canes originate) are genetically different suckers (from the understock or rootstock) that must be removed.

As growth resumes in spring, well pruned plants will produce fewer stems and blooms that are significantly more vigorous than those of inadequately pruned plants. Overgrown and inadequately pruned plants must spread their resources thin amongst more but significantly weaker stem growth that is much more likely to be damaged by pathogens. Aggressive pruning now pays off later.