Many people imagine that in some mysterious fashion plants eat soil much as we eat beef-steak; and that, all soil being just "soil," one has but to make a hole in the ground and thrust the roots of a plant into it, in order to make the desert bloom as the rose. This idea is incorrect, just as was the idea of a Devonshire farmer whom I once saw feeding his month-old baby with cheese and cider. "Feed 'un on milk?" said he. "I'd zooner gee 'un zope-zuds. Let 'un 'ave summat wi' zum strength in't."

Soil is to plants not a source of food alone, but is a suit of clothes, a blanket and coverlet, a cooking-range and a drawing-room fire. It is a pied-À-terre in its most literal sense, and it is a cellar and tankard combined. To all the great and beautiful world of flowers, the soil is indeed mother earth, giving them warmth and nourishment in their infancy, affording them a root-hold throughout their life, and offering them sanctuary for their bodies when their earthly life is done.

He who would grow beautiful flowers must therefore first study the soil from which he would raise them. He must get to know it, to learn its wants, and learn also how he may best satisfy them. In time, if he be indeed a lover of flowers, he will grow also to love the earth and to understand it. He will become one of those true and happy gardeners so beloved of the gods that every flower they lovingly plant is made to flourish and multiply.

First, then, let us think of what this soil is made, and of how it came into being. Look at the surface of any old stone-built church or house and you will see how every stone is partly covered by moss or lichen or other lowly plant. These plants are growing in soil—formed by the slow action of rain and air on the surface of the walls. Similarly, in the gradual pulverisation and decomposition of rocks, has all soil taken its origin. Similarly also, as a rule, have lowly plants been its first offspring, the bodies of which have been afterwards incorporated with their mother soil. By the further action of the weather, coupled with the action of the accompaniments of the decomposition of these early plants, the soil becomes deeper, and becomes also furnished with dead vegetable matter, or humus, without which none of the higher and more developed plants are able to live.

According to the nature of the original rock, and according also to the sort of natural "weathering" or "watering" to which it has been subjected, so will the resultant soil be mainly sand or mainly clay, or an equal mixture of the two. Mixed with these will usually be found a certain amount of little stones or gravel, and a certain amount of dark coloured humus. In a soil which is nearly all sand, or in one which is nearly all clay, few flowers will thrive, but in what is called a loamy soil—that is, one in which clay and sand are nearly equal—nearly all plants will grow and prosper if other conditions be favourable. The presence of humus in the soil is important in many ways, for not only does it contain much that is essential food for plant growth, but also it assists the earth in retaining that moisture without which life is impossible. By its chemical activity, also, it produces useful heat and liberates stores of food from the mineral soil itself. Therefore it is that we add dead leaves, farmyard manure, sea-weed and the like to our garden soil. But, though moisture is essential to the health of plants, the presence of stagnant water is little less fatal than drought. If we find that a hole dug in our gardens to the depth of two feet soon contains water not obtained from above, we may usually assume that drainage is required.

If our soil be too light (i.e. sandy) we may improve it by the addition of dried and powdered clay, meal and organic manure, from cowshed or stable; if it be too heavy (i.e. containing an excess of clay) we may make it more suitable for our garden use by mixing with it sand, ashes, lime, gritty road-scrapings, or old mortar.

We all know how very much hotter in summer and colder in winter is a starched linen shirt than is one made of flannel or of some cellular open-woven fabric. This is of course due to the fact that the former is the better conductor of heat. In like manner, a loose, cellular, "open-woven," porous soil is a much worse conductor of heat than the caked and baked soil which we often see in ill-kept gardens.

The roots of plants like coolness in summer, but in winter they desire all the warmth that they can obtain. Hence the desirability of always maintaining the surface of the ground to the depth of an inch or two in a loose open condition by means of the hoe. This is of value also in checking evaporation, for, by keeping the surface inch of soil loose and fine, the capillary connection between the air and the deeper layers of soil is broken. Surface mulchings of litter, moss, leaves or manure act in the same way as does the simpler mulch of hoed soil. Of course the process of top-dressing with leaves or farm-manure, in order to add to the soil the food elements which they contain, is quite a different matter, and cannot be replaced.

Very few gardeners can be said to make anything[89][90] approaching adequate use of the soil which they cultivate. The majority of amateur gardeners, and not a few professional ones, never get their spade more than a foot or, at the outside, more than eighteen inches below the surface. As a matter of fact, all garden soil should be dug to a minimum depth of two feet, or preferably to a depth of three feet when possible. In preparing a piece of ground for planting, it should, therefore, be trenched as deeply as possible, preferably to a depth of three feet.

This operation may be performed as follows:—

Let A B C D represent the piece of ground to be trenched. Measure off A E, E G, G M, D F, F H, and N H, each the distance of one foot. Stretch a line from E to F and notch the surface with a spade along this line. Proceed in the same way from G to H. Next dig the piece A E F D to a depth of one foot, wheeling this surface soil to form a heap at B. Also dig to the same depth the piece E G H F and add this soil to the heap at B. Next remove the subsoil from the piece A E F D to the depth of another foot, and wheel it to C. The deeper subsoil in the piece A E F D should then be dug to a depth of another foot and left in its old position. The subsoil from E G H F to the depth of a foot should now be placed with the spade on A E F D, and the deep subsoil below it dug and left in situ. A layer of farm-yard manure may next be placed on the A E F D, and on this should be placed the top foot of soil from G M N H. The subsoil from G M N H should next be placed on E G H F, on this being placed a layer of manure covered in turn by fresh top soil. In this the work should be proceeded with until the last two feet of the patch are reached. The subsoil from I B C J is to be placed on the deep subsoil of K I J L, on this a layer of manure covered by one half of the surface soil in the heap at B. The heap of subsoil at C and the remainder of the surface soil at B are to be placed in the space I B C L.

This proceeding may strike the novice much as a problem of Euclid strikes the mentally lazy, but the importance of deep cultivation is so great that everyone who would be a successful gardener should thoroughly understand its practice. By the method of trenching above described, the three layers of earth called here soil, subsoil and deep subsoil are maintained in their respective orders of depth, for nothing is more fatal than to bury the "living earth" of the surface below the reach of the roots of our plants, bringing to the surface in its place the barren subsoil devoid of humus and devoid of those living bacteria so essential to the fertility of the soil. By proper and continuous cultivation, the actual living soil attains an ever increasing thickness, so that in time the top two feet may be correctly described as surface soil and become freely interchangeable throughout its thickness.