Drainage.—Let us suppose we contemplate making a new rose-bed on some portion of pasture land. The first thing to consider is drainage; is it by nature well drained? If not, we must resort to artificial drainage. To settle this point, note the herbage; fine herbage denotes a well-drained soil; but if, on the other hand, the grass is coarse and in tussocks, it is a sure sign that the land requires draining. There is little land in England naturally so dry as not to be susceptible of improvement by artificial draining. Land is not in perfect condition unless the rain can penetrate to a depth below that of the root of a rose plant. We want the roots to go down; stagnant water checks this descent, because a water-logged soil destroys all capillarity, which means to the plant suffocation and starvation. It is well known that plants growing in a deep soil lying on a porous subsoil seldom or never suffer from drought, whilst the soil which soonest becomes saturated in wet weather is that which is the quickest to get dry and cracked in times of drought. We therefore drain the land to save rose plants from being drowned in wet, or parched in dry weather.
But draining does more than this, it raises the temperature of the soil; and the higher the temperature of the soil the earlier and later the roses will bloom. Soils that are naturally dry are usually described as warm and early, and conversely, wet soils are invariably spoken of as cold and late. This classification is quite correct, and the explanation not far to seek. An excess of water in the soil keeps down its temperature in several ways. The water in passing into vapour draws off the heat which the soil has obtained from the sun. Water also has a high radiating power, but stagnant water conveys no heat downwards, for although the surface of the water is warmed it remains on the top, it never descends to carry the heat below. Now where the rain water can penetrate to a depth of several feet, and can pass through to the drainage, it carries with it the heat it has acquired from the atmosphere together with the sun-heated surface of the soil. Therefore in well-drained land the messenger boy brings heat downwards as well as plant food.
We may not be able to choose our climate, it may be late or it may be early—there it is, we cannot improve it; but this we can do, if the soil be wet, and consequently cold, we can raise its temperature by artificial drainage, and thus insure a crop of autumn-flowering roses.
As will be presently noted roses require a deep soil in which to work, and the deeper it is the more room there is for storage of water; water passing up and down, but not stagnant. I advocate that the soil in a new bed should be broken up down to a depth of 3 feet, and therefore the drain should come just below. Of course if the soil is naturally light and porous to a considerable depth no artificial draining is necessary; if the subsoil is gravel or sand so much the better, provided we have 3 feet of good soil on top. But where a heavy, impervious subsoil of clay takes the place of gravel, then a land drain 4 feet deep or more is essential. I have dealt at some length on this point because in many cases where the rose crop is a failure it is due to neglect of draining.