April 15 is usually a safe date to prune roses. The worst of the freezes are probably behind us, so any new growth generated by pruning should survive whatever cold snaps occur before summer.
This may vary by microclimate with some areas more likely to freeze harder than others. Microclimates can even fluctuate on one piece of property such as the north side being colder than the south side. Pruning before April 15 often results in rose canker disease developing in the rose canes below the pruning cut. Then, in removing the infected stems there may be nothing left to grow.
We often prune to make a bush look better, but pruning also encourages a healthy plant with more blooms. With pruning, we can eliminate damaged, dead or crossing stems. Roses three years or younger need little pruning.
Roses are disease prone, so sharp disinfected tools are necessary. Dull tools damage rose stems, creating wounds that invite disease organisms. Tools that haven’t been disinfected with something like alcohol also transmit disease.
It is wise to disinfect between cuts not only on a single rose but also across multiple roses. Bypass shears and loppers make clean cuts rather than smashing the stem as anvil shears sometimes do. A smashed stem is an invite to disease. A pruning saw is a good tool for heavy old stems.
Cuts should be made ¼-inch above an outward facing bud. The direction the bud is going will be the direction of growth. The Utah Rose Society recommends removing “about one-third of the overall height or one foot lower than desired ultimate height” (http://utahrosesociety.com/rose-pruning/). Remove and throw away all old canes, stems, leaves, etc. to eliminate sources of disease. Don’t compost rose materials.
There are many types of roses, which require different pruning techniques for optimum bloom. Check out the Utah Rose Society site for specifics.
Rose canes should be sealed after pruning with white school glue to prevent rose cane borers from destroying the stem. Just dab a tiny bit of glue on the cut end.
Before following rose-pruning advice, check what part of country the information is written for. Too often, it comes from areas where there are moist, humid winters and roses don't dry out. Their skies may be dreary for months, sheltering plants from the sun.
Here, we generally have sun and wind in the winter with little moisture. Rose canes and crowns often die back in the face of drought and desiccating winds.
JoAnne Skelly is an associate professor & extension educator emerita of the University of Nevada Cooperative Extension.