The roots through whichderive their nourishment are, in the main, the fibrous ones which grow near the surface of the . It takes only a few weeks of very dry weather in spring, especially in light soils, to make you appreciate why soil moisture must be conserved. Mulching – spreading a layer of material over the bed between the plants – will conserve not only moisture but also food and, in addition, it will protect the precious roots from extreme coldness of the soil caused by harsh, drying winds during the early weeks of spring.
The mulch should preferably be loose in texture so it will not prevent air getting to the roots. If you use well-made or farmyard manure as a mulch it should be well broken down before applying to a thickness of 50 mm (2 in) all over; this will also provide additional food. It is best to apply the mulch before too much development has taken place in the young growth of the roses: mid-April can be taken as a general guide. Too early an application will keep the soil too cold.
Many materials can be used for mulching, but if they are short of plant nutrients it is a good idea to give first a dressing of one of the compound fertilizers specially prepared for roses.
Peat has become very popular as a mulch, but it must be well soaked before applying; if it is applied dry, rain has difficulty in penetrating it, and it is also apt to blow away in strong winds.
Lawn mowings are frequently used, for mulching is a convenient means of disposal, saving many journeys to the compost heap; but do not use them if you have treated your lawn with a selective weed-killer. Unfortunately, many lawns include annual meadow grass (Poa annua) in their composition, and this will readily take root. In general, then, there is much to be said for consigning mowings to the compost heap and allowing them to become thoroughly composted before applying them to the rosebed. But if you do use them straight from the lawn, sprinkle them thinly over the bed so as not to form an impenetrable mat over the surface. Spent hops are also useful for mulching or improving the soil. Pulverized bark has received much publicity in recent times because of its value in horticulture, and it has been widely used as a mulch. In its favour is its appearance; it is better looking than lawn mowings, and it is less attractive to birds than farmyard manure. Opinions differ about its effect on the soil, but it is worth a trial if you can afford it.
Owing to the shortage of farmyard manure, particularly in towns, compost has become almost a cult with some gardeners, and many strange mixtures and concoctions are favoured. However, if all house and garden waste of animal or vegetable origin is saved and decomposed, much useful material will be made available both for improving the soil and for mulching. Much has been written about compost by fanatics as well as by many level-headed horticulturists. As a good supply of organic material is of great importance in the growing of roses, a few remarks about the principles involved in its production deserve a place here.
It is a considerable advantage to have at least two compost bins. Their bases should be open on the soil, and their sides should have openings to allow air to penetrate and encourage useful bacteria in their work of decomposing the waste materials. The material is best introduced in layers about 120 mm (5 in) deep; if possible close-packing materials such as lawn mowings should alternate with looser materials such as straw, bracken, garden waste, and so on. Sprinkle on some lime every few layers. It will also help to add a little manure or some soil containing a nitrogenous fertilizer. Very dry materials such as straw or old hay should be dampened, but do not soak the mass as this will impede the circulation of air; the top of the compost bin should have a cover to keep out heavy rain.
The compost should be built up layer by layer to a height of about 1 m (3 ft). When the compost in the first container shows signs of becoming decomposed, it should be transferred to another. When doing this make sure that the less-well composted material from the top and sides is put in the middle and is covered by the most highly decomposed. Fresh material, as it becomes available, should be placed in the first container. When the compost is used for roses, either as a soil improver or for mulching, it is advisable to add a few handfuls of sulphate of potash in order to balance up the nutrient value. The finished product should be a dark brown powder, easy to apply and spread — not the glutinous, smelly mess that sometimes passes for compost.