Roses grow best in sites with full sun, well-drained soil and good air circulation. Plant roses with the graft union (if there is one) one to two inches below the soil line to protect the graft from our severe winter temperatures. All types of roses need at least one inch of water per week during active growth. Fertilize roses with an all-purpose fertilizer, such as 8-10-8, every four to six weeks during the growing season. Discontinue fertilizing on August 15 to prevent late succulent growth prior to the first frost.
The style of pruning is the main cultural difference between shrub or old garden roses and modern hybrids. Shrub and old garden roses should be pruned once a year in early spring. Remove dead, old, diseased, crossing and weak canes at ground level. Do not remove the faded blossoms because this will eliminate the rose hips which are attractive in fall and winter. The exception to removing old blooms, is on roses that flower twice a season. Deadhead these roses after the first flush of bloom only.
Modern hybrid roses are pruned to a V-shape with an open center. Prune when the buds start to swell in the spring, removing all dead, weak and crossing canes. Ideally, the canes would be left eight to ten inches tall, but because of the severe winters here, there may be only two to four inches left. The final cuts should be one-quarter inch above a healthy, outside-facing bud, at a downward sloping 45 degree angle away from the bud.
Pruning is an all-season activity with modern hybrid roses. As dead blossoms are removed, the resulting cuts should be made one-quarter inch above a five leaflet leaf, leaving at least two mature leaves on the stem. From September on, don't deadhead modern hybrid roses. This will force the plants to begin going dormant before the first hard frost.
For more information, see the following Colorado State Extension fact sheet(s).
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Updated Friday, April 19, 2013