|PHOTO/UGA Horticulture Specialist Bob Westerfield|
Clemson University's "Ask a Master Gardener" publication "Pruning Knockout Roses: When and How," says "Rose pruning should be done just as buds break dormancy...probably around late February or early March. When the buds have swelled but no new growth has yet appeared, it is the ideal time to prune bush or shrub type roses."
North Carolina State University (NCSU) Extension's "Pruning Knock Out Roses" agrees with that timing, saying "Rose pruning should be done just as buds break dormancy, usually around mid-to-late February or early March in Zone 7. A good rule of thumb to help you remember is 'prune your roses when the forsythia is in bloom.'"
NCSU's instructions include the qualifiers, to wait until the second and possibly even the third year of growth before pruning, and that some shaping and thinning can be done in the summer, if needed. This summer thinning is especially useful to eliminate any points of contact where branches touch or rub against each other, to reduce spots where disease might enter the plant.
Clemson's publication explains the best method of figuring out where on the cane to make a pruning cut:
"Prune the bush to make it more open in the center. This will increase air circulation and help prevent diseases. Since rose bushes send out new growth from the bud just below a pruning cut, try to make pruning cuts above a leaf bud facing out from the center of the plant. Make a cut 1/4 inch above the bud and angled at the same angle as the bud."
UGA's Georgia FACES article "Prune Roses Now for More Blooms Later," by UGA Extension's Frank Watson, adds an emphasis on checking the pith, or center, of the stem after it's been cut. If the center is creamy white or greenish, then the stem is healthy, but if it is brown or black, Watson recommends "continu[ing] to cut down the cane until green or white pith is revealed. In some cases this may mean a drastic reduction of the cane. Occasionally, the pith will become darker with each successive cut, and the cane will have to be removed at the bud union using a small pruning saw."
For further information, read the complete articles at the links as they appear above.
For those who have not planted Knockout roses, but who are planning to, the UGA publication "Roses in Georgia, Selecting and Growing Techniques," by Horticulturists Bob Westerfield and Malgorzata Florkowski and Technical Assistant Adrianne Todd, provides a clear and easy-to-follow description of how to plant and care for your new roses, to promote abundant bloom.