Pruning is a simple and necessary part of keeping a rose healthy, strong and blooming. If you prune the rose wrong, you may not get a lot of flowers the following year, or none at all, but there is no wrong way to prune that will kill an established rose.
If anything, if you can live with a couple of years of no flowers, the rose will get a lot of rest and renewed energy for new growth.
Why prune roses
There are four reasons to prune roses: remove old and diseased canes to make room for more growth, allow air movement, shape the bushes to your liking and encourage blooming.
What roses to prune
1. Do not prune shrub, species and old garden roses (the once a year blooming roses) in spring! Some examples would be Albas, Damasks, Moss Roses and Gallicas. These roses generally have a tall growth habit and bloom on old wood. If you prune them in spring, you will cut out all the new year’s flower growth. Prune after blooming to remove diseased canes, make sure there is enough air movement to keep the rose bushes healthy and promote new growth. Allow the tall Albas and Centifolias to reach their full height and prune only laterally. Wait for two years before starting pruning, because flowers appear on second year wood.
2. For modern roses such as Hybrid Teas, Floribundas, Grandifloras, and Hybrid Perpetuals prune with confidence up to 2/3 of the plant growth. They will grow back stronger for it. Remove canes that are larger than 1/2 inch in diameter and everything in the middle of the bush, to allow plant to develop and prevent overcrowding. Remove any canes that have winter damage. Leave three or four well spaced young canes per bush, making sure that growth is outward facing (see section about pruning cuts).
3. Cut back Bourbons by 1/3 of growth, after a couple of years. Remove lateral shoots.
4. Do not prune young roses and newly planted roses at all. They need all the growth they have.
5. For Miniature roses and Polyanthas, clean out dead and diseased canes and then cut them back to the height you want.
6. For landscaping roses, you can take the hedge shaper and cut across to the height you want.
7. Climbers and Ramblers, regardless of the fact that they are single or repeat bloomers should be pruned during the dormant season. Do not prune at all during the first two or three years, just remove the dead canes. After that prune back only old canes enough to remove clutter and promote new growth. Ramblers bloom on second year wood, so prune cautiously.
How to prune roses
The general rule of thumb for pruning cuts is a 45 degree cut that is made 1/4 inch above an outward facing bud, with the cut facing towards the inside of the bush. Remove all crossing, diseased or winter damaged canes. Remove old woody canes and canes larger than 1/2 inch in diameter.
When to prune
Prune old roses after they finished blooming to allow new growth before the cold season.
Prune perpetual blooming roses at the end of winter, beginning of spring, when new buds start developing. Pruning too early encourages roses to generate new shoots that get damaged by frosts, pruning too late makes the plant expend a lot of energy on growth that will be removed anyway. A good rule for the Midwest is to prune roses when the forsythia blooms.
Last, but not least, always use sharp clean pruning shears. I recommend disinfecting them with alcohol to prevent the spread of disease to the roses while pruning.