Pruning promotes growth. Every cut results in healthy growth that will eventually bear flowers.
Pruning determines plant shape. Every cut causes growth to head in a specific direction. If you want your rose to grow a certain way, you can position cuts to coax growth toward that shape.
Annual pruning helps deter disease. When you prune to remove older or crossing stems in the center of the bush, you make it easier for sunlight and air to reach between branches. Increased air flow and sunlight dries wet leaves more quickly, which helps prevent disease outbreaks.
Pruning keeps a rose healthy. Whether canes are diseased, damaged or dying, a simple snip eliminates the problem and encourages remaining stems to grow stronger.
What You Need to Prune Roses
For basic pruning on recently planted roses, you only need leather gloves to protect hands from thorns and a pair of sharp hand pruners (bypass pruners are best). If you have more mature roses, you will likely also need a pruning saw and loppers. If you're dealing with very thorny canes, look into rose gloves that extend beyond the wrist to protect against scrapes.
If you garden in an area where you know that Rose Cane Borers are present and active, you will also need white glue to seal cut stem ends.
When You Should Prune Roses
In coldest regions: Prune at the end of winter. Wait until after the last frost, just before buds begin to swell.
In more moderate zones: Roses frost several times but may never lose all leaves. In these areas, prune during the coldest part of the year, when growth slows – and before buds begin to swell. This should correspond to 3-4 weeks before the average date of the last killing frost. Prune on a day when canes are frost-free.
In warmest zones: Roses may never enter a complete dormancy or fully lose leaves, but plants will enter a slow-growth phase during the coldest part of the year. That is an ideal time to prune roses.
Timing Tip: In coldest and moderate areas, where freezes can kill, pruning timing is critical. Prune too soon and the rose will be more dormant than awake. Stems will not have greened up, and new growth will appear low on canes. A subsequent hard freeze will kill new growth and possibly even the plant. If you prune later, as recommended, the rose will be more awake, and new growth will start toward branch tips. A late freeze will only damage upper portions of the plant, and the base will remain alive.
How You Should Prune Roses
Make cuts on stems about 1/4 inch above a bud and at roughly a 45-degree angle sloping away from the bud. Growth will begin from the bud just below where you cut. Place your cut so that new stems will grow in a direction you want.
Canes that are dead or dying
Canes that rub against another cane (remove one of them)
Canes damaged by insects, diseases or storms
Canes thinner than a pencil
How Much You Should Prune
Once you remove problem growth, you can substantially shorten your roses or just take a little off the top. The more you shorten your bush (the harder you prune), the fewer, larger flowers you will have. Prune less, and you will have many smaller flowers.
In terms of inches, cut plants back to 12-15 inches for few, large flowers; to encourage many smaller-sized blooms, cut plants back to 18-24 inches.