Prune hybrid perpetual and most other hardy roses in April when sap begins to flow and buds start to swell. At this time dead wood may be most easily distinguished and mulch should not be disturbed earlier. Memorial roses and rambler roses should be pruned just after the flowering season to produce wood for the next year's bloom.
Other things being equal, the pruning determines the quantity and size of flowers. Severe pruning will produce the largest and best flowers; less severe pruning is productive of a large crop of average flowers; medium pruning produces a large crop of smaller blooms (Plate V, Page 24).
For severe pruning, thin out to the base all but three to five shoots, with two to three buds on each shoot. Less severe pruning requires the same number of shoots to be cut back to from five to ten buds. For medium pruning, leave four to seven shoots and cut each back to one-half of its height. Always cut the stem one-fourth to one-half inch immediately above a strong bud that points out from the centre of the plant. When a plant has been pruned the shoots should be left as nearly as possible equi-distant from each other and arranged around the plant, so that it presents a well-balanced appearance on all sides with an uncrowded centre. With some hybrid perpetuals and climbers, if considerable length of stem is cut with the flowers, the plants can be induced to make some autumn bloom. Seeds should never be permitted to ripen on rose bushes, as the effect of this is extremely weakening to the plant.
When pruning hybrid perpetual roses remove branches that cross, and all weak wood also. Cut back strong canes to six buds, the top bud pointing outward. For a big outdoor display leave two-thirds of the length of four to seven canes. Sometimes it is feasible to cut away part of the tops in autumn so that the fibrous roots will not be loosened or broken by the force of winter winds swaying the plants.
Hybrid teas and teas must be cut to the surface of the soil, if necessary, in order to cut to live wood. However, as much or more wood should be left as on hybrid perpetuals, if possible. Weak growers should be cut back farther than strong growers.
Rugosas, bourbons, chinas, austrian briers, ramblers, and wich-uraianas need but little pruning. Thin out and cut back only a few inches of the stems. Remove wood to the base of the plant as it becomes old.
Climbing and pillar roses need only one-third to one-fifth of the wood removed. All old wood should be removed about once in three years. In autumn any unusually long canes should be cut back slightly and tied up.
When rose blooms are cut from the plant the finest and largest blooms follow if only one bud is left to the branch.