Pruning roses is one of the gardening jobs that come round every year, but there is some controversy as to when is the best time to carry out this task. The general principle is clear that removal of dead and diseased branches and pruning back the excess stems will ensure that the bush looks its best for the coming season. I found an article by Kym Pokorny on the OSU Extension Service website which explains when and how to complete this task.
On the west side of the Cascade Range, mid-February is generally time to start thinking about pruning, according to Amy Jo Detweiler, a horticulturist with Oregon State University?s Extension Service. In Central Oregon, April or May is the best time. In both cases, take your cue from the plants. When the buds begin to swell and get ready to break open, pull out your pruners.
Detweiler recommends using bypass pruners rather than anvil because they cut more like scissors and won?t crush the stems. Make sure they are sharp. Have some rubbing alcohol on hand to for dipping the blades in between cuts, especially as you move from rose to rose.
As you get started, stand back and survey the rose. First cut out any dead, diseased or damaged wood (also called canes). Remove anything smaller than a pencil. Then find three to five of the healthiest canes and clip those back uniformly to 14 to 16 inches above the ground. Make your cut just above a bud that faces outward and prune at a 45-degree slant.
?You want the shrub to grow outward so that the center remains relatively open,? Detweiler said. ?That increases air circulation and reduces the chances of disease.?
See more at OSU Extension Service