Mulching helps to keep the soil moist, keeps its temperature steady, gives the roses a cool root-run. In addition, as the substances used for mulching provide humus they help to condition the soil and supply slowly-released plant foods. A mulch also keeps down weeds. It is also claimed that, because it prevents rain from splashing up from the ground on to the lower leaves of a rose bush, it reduces the spread of blackspot.
Summer Because weeds steal the moisture and plant foods intended for the roses, their suppression is important. The principal methods of doing this are : physical methods i.e. regular hoeing; mulching and chemical methods. The two main types of chemical weedkillers are:
Pre-emergent: this sort interferes with the growth of the seedling leaves and they do not emerge from the soil. It is applied in the early spring.
Often during the spring, three shoots emerge from one bud center. As soon as they are large enough to handle, the outside growths should be pinched off, and the center one, which is usually the largest, should be allowed to develop.
Suckers are shoots that originate low down on the rose tree or beneath the ground. They grow from the root-stock and not the scion or budded variety. If they are allowed to remain, they sap nutriment from the main stems. The most satisfactory way of discerning a sucker is to note from which position it originated. If the shoot appears from below the union or from the root, it is a sucker and should be torn out, not cut away, at its point of origin, scraping away the soil, if it appears from below the ground. By tearing it out, the whole budding system is destroyed and there is little chance of it reappearing.
Some hybrid tea roses, instead of growing one terminal bud, develop three on a stem, while others grow their flowers in clusters. Disbudding consists in removing all the side-flowering shoots, when they are just large enough to handle, leavingoneterminal flowering bud. Whether this is carried out is largely a matter of personal taste. Nothing should be done if a good, massed display of color is desired, but iflarge perfect individual blooms, say for showing, are required, it should be carried out .
If there is to be good repeat flowering, removing the spent blooms as soon as they fade is essential. The stems should be cut off at the first outward growing leaf with five leaflets to avoid removing too many leaves, which are important because they are part of the apparatus by which the plant produces its food from light (photosynthesis).
When watering, the blooms and the leaves should not be wetted, because the former will become blemished and moisture on the latter will encourage fungus diseases. The use of a perforated hose, turned upside down and interwoven among the plants avoids these possibilities.
Fall and Winter To prevent bush roses from being whipped by winds, cut back tall stems in November to halfway.