Instructions in gardening for ladies

by Mrs. Loudon

CHAPTER II.

MANURING THE SOIL AND MAKING HOTBEDS.

Most persons imagine that manure is all that is wanted to make a garden fruitful; and thus, if the fruit-trees do not bear, and the flowers and vegetables do not thrive, manure is considered the universal panacea. Now, the fact is, that so far from this being the case, most small gardens have been manured a great deal too much; and in many, the surface soil, instead of consisting of rich friable mould, only presents a soft black shining substance, which is the humic acid from the manure saturated with stagnant water. No appearance is more common in the gardens of street-houses than this, from these gardens being originally ill drained, and yet continually watered; and from their possessors loading them with manure, in the hope of rendering them fertile.

As it is known to chemists that it is only the humic acid, and carbonic acid gas, contained in manure, which make that substance nourishing to plants; and as these acids must be dissolved in water before the roots can take them up, it may seem strange that any solution of them in water, however strong it may be, should be injurious to vegetation. The fact is, however, that it is the great quantity of food contained in the water that renders it unwholesome. When the roots of a plant and their little sponge-like terminations, are examined in a powerful microscope, it will be clearly seen that no thick substance can pass through them. Thus water loaded with gross coarse matter, as it is when saturated with humic acid, must be more than the poor spongioles can swallow; and yet, as they are truly sponge-like, their nature prompts them, whenever they find moisture, to attempt to take it up, without having the power of discriminating between what is good for them, and what will be injurious. The spongioles thus imbibe the saturated liquid; and, loaded with this improper food, the fibrous roots, like an overgorged snake, become distended, the fine epidermis that covers them is torn asunder, their power of capillary attraction is gone, and they can neither force the food they have taken up, into the main roots, nor reject the excrementitious matter sent down to them from the leaves, after the elaboration of the sap. In this state of things, from the usual circulation of the fluids being impeded, it is not surprising that the plant should droop, that its leaves should turn yellow, that its flowers should not expand, that its fruit should shrivel and drop off prematurely, and that in the end it should die; as, in fact, it may be said to expire of apoplexy, brought on by indigestion.

All soil, to be in a fit state for growing plants, should be sufficiently loose and dry to allow of water passing through it intermixed with air; as water, when in this state is never more than slightly impregnated with the nutritious juices of the manure through which it has passed. The spongioles are thus not supplied with more food at a time than they can properly take up and digest, and a healthy circulation of the fluids is kept up through the whole plant. But, what, it may be asked, is to be done with a garden, the soil of which has become black and slimy like half-rotten peat? The quickest remedy is covering it with lime, as that combines readily with the humic acid, and reduces it to a state of comparative dryness: or, if the sub-soil be good, the ground may be trenched, and the surface-soil buried two spits deep; in either case it will be necessary thoroughly to drain the garden to prevent a recurrence of the evil.

All the different kinds of soil found on level ground, consist of two parts, which are called the surface-soil and the sub-soil; and as the sub-soil always consists of one of the three primitive earths, so do these earths always enter, more or less, into the composition of every kind of surface-soil. The primitive earths are—silex, (which includes sand and gravel,) clay, and lime, which includes also chalk; and most sub-soils consist of a solid bed or rock of one or other of these materials, probably in nearly the same state as it was left by the deluge. The surface-soils, on the contrary, are of comparatively recent date; and they have been slowly formed by the gradual crumbling of the sub-soil, and its inter-mixture with decayed animal and vegetable matter, and with other soils which may have been accidentally washed down upon, or purposely brought to it. In fields, and uncultivated places, the surface-soil is almost as hard, and as coarse in its texture, as the sub-soil on which it rests; but in gardens which have been long in cultivation, the surface-soil becomes so thoroughly pulverized by frequent diggings, and so mixed with the manure and decayed vegetables which have been added to it from time to time, that it is changed into the soft, light, fine, powdery substance, called garden-mould. If the sub-soil be naturally porous or well drained, this mould, however rich it may be made by the addition of decayed vegetable matter or animal manure, will always continue friable; and as long as it does so, it will be fit for the growth of plants: but if no vent be allowed for the escape of the water, and it be continually enriched with manure, it will be changed in time into the black slimy substance that has been already described.

Surface-soil is called peat-earth when it is composed of decayed vegetable matter, without any mixture of animal manure; and, as this excess of vegetable matter could neither be produced nor decayed, without abundance of stagnant moisture, this kind of earth is almost always found on a clayey sub-soil, which prevents the water which falls upon it from escaping. Peat-earth has a spongy, elastic feeling when trodden upon, arising from the quantity of water that it holds, and it can only be rendered fit for cultivation by draining. In its elastic state it is what is called in Scotland a moss, and in England a peat-bog. Should the water, instead of being afforded a vent by drainage, be suffered to accumulate for many years, till it completely saturates the peat, the soil becomes what is called a morass, or quagmire; and it can no longer be trodden on, as it will engulf any substance resting upon it. A still further accumulation of water will, in the course of years, cause the bog to burst its bounds, and overflow the surrounding country; as the Solway-moss did many years ago, and as bogs in Ireland have done frequently. An excess of vegetable matter on a silicious sub-soil, differs from the common black-peat in retaining less water; and in being mixed with a portion of the primitive earth, which, from its loose texture, becomes easily detached from the sub-soil. Peat in this state is called heath mould.

The most productive soils are those in which several ingredients are combined in proper proportions; and if any one of the primitive earths preponderates, the soil becomes comparatively unfertile. Thus the best soil for gardening purposes is generally allowed to be a calcareous loam on a chalky sub-soil; and this sort of soil is composed of nearly equal parts of lime, sand, and clay, enriched depositions of decayed animal and vegetable matter. The next best soil is a sandy loam, composed of clay and sand, enriched by decayed animal and vegetable substances, and resting on a sandy or gravelly sub-soil. The worst soils are peat and sand. A poor sandy soil is necessarily a nearly barren one; because it will not retain either water, or the nutritious juices from manure, long enough to afford nourishment to the plants grown upon it; and it is obvious that a soil of this kind can only be rendered fertile by mixing it with clay; which would change it into a sandy loam.

A stiff clay is unfertile from its attracting moisture and retaining it round the roots of the plants till they become swollen and unhealthy. It also retards the decomposition of manure, and obstructs the progress of the roots, which waste their strength in the efforts they make to penetrate, or twine round, its adhesive clods. Soils of this description are improved by a mixture of sand, gravel, road grit, or any substance which tends to separate the particles of the clay, and to render it light and friable.

Chalky soils succeed better unmixed, than any of the other kinds; but chalk being a carbonate of lime, can hardly be called a primitive soil. The chalk, however, from its whiteness is colder than any other soil; as it does not absorb, but reflects back the rays of the sun. Rain also penetrates into it very slowly, and not to any great depth. Chalk mixed with sand forms a kind of calcareous loam admirably adapted for growing vegetables; and chalky soils are peculiarly susceptible of improvement from manure.

Manures.—The kinds of manure generally used in gardens are horse or cow dung, and decayed vegetable matters; the manure in both cases being suffered to lie in a heap to rot before it is spread on the ground, in order that its component parts may be decomposed by fermentation, and thus brought into a fit state to afford food to the plants. Old hot-beds or mushroom beds are thus well adapted for manuring a garden; and when fresh stable-dung is employed for that purpose, it is generally thrown into a heap, and turned over several times till the fermentation has abated, before it is dug into the ground. As, however, a great quantity of carbonic acid gas is evolved and escapes during the process of fermentation, and as it seems a great pity that so much of the nutritious properties of the manure should be lost, it is now customary to cover the dunghill with earth, into which the gases will rise during the process of fermentation, and in which they will deposit the greater part of their nutritious properties. A quantity of earth should also be laid round the dunghill to imbibe the liquid that runs from it, and this earth, part of which must be removed and fresh added every time the dunghill is turned over, will be found very nearly as valuable for manuring the beds of a garden, as the manure itself.

The modes of applying manure differ according to the difference of the soils. For sandy loams, thoroughly rotten dung, either from an old hotbed, or from a dunghill sufficiently decayed to be cut easily with the spade, or the earth that has covered a dunghill during the process of fermentation, should be laid on the surface of the soil, and dug in. In very poor sandy soils rotten manure, or earth from a dunghill, should be laid on the surface of the soil, and not dug in: being covered, if hot dry weather be expected, with leaves, straw, or the branches of trees cut off in pruning; or occasionally sprinkled with water. Soils of this description, and loose sands, are frequently improved in the South of France and Italy, by sowing them with seeds of the common white lupine, and then, when the plants have come up and grown about a foot high, ploughing or digging them into the soil. The green succulent stems of the lupines, when thus buried in the soil, supply it with moisture during the process of their decay; and thus nourishment is afforded to the corn, which is immediately afterwards sown upon the soil for a crop. Clayey soils should have unfermented manure mixed with undecayed straw laid in the bottom of the furrows made in digging; that the process of fermentation, and the remains of the straw may operate in keeping the particles of the soil open, or, in other words, in preventing their too close adhesion. Lime (though when burnt it becomes violently caustic, and will destroy and waste all the manure applied with it), as carbonate of lime, or chalk (in which state only it can properly be called a soil), retains the manure applied to it longer than any other soil. Rotten manure may thus be dug into chalk, with the certainty that it will be preserved from farther decay for a very long time, and that every shower will work a small portion of its fertilizing juices out of it, and carry them into the soil, where they will be thus presented to the plants in the best possible state for affording wholesome food.

Peat soils may be improved by the addition of quick-lime as a manure, which will absorb the superabundant moisture which they contain; or they may be mixed with sand, gravel, or clay to give them firmness and tenacity, and then with a small quantity of animal manure. Sandy peat or heath mould is very useful in gardens for growing heaths, rhododendrons, kalmias, or any plants with fine hair-like roots; and from the quantity of vegetable matter that it contains naturally, it does not require any manure, more than what is furnished by the decaying leaves of the plants grown in it.

Nearly the same rules apply to decaying leaves and other substances used as manure, as to stable-dung. They may be buried in an undecayed state in clayey soil, when it is the object to separate the adhesive particles of the clay by the process of fermentation; but their component parts should be separated by fermentation before they are applied as a manure to growing plants. Vegetable mould (that is, leaves thoroughly decayed and mixed with a little rich loam) is admirably adapted for manuring the finer kinds of flowers, and plants in pots. There are many other kinds of manure used in gardens occasionally; such as the dung of pigs, rabbits and poultry, grass mown from lawns, parings of leather, horn shavings, bones, the sweeping of streets, the emptying of privies, cess-pools, and sewers, the clipping of hedges and pruning of trees, weeds, the refuse of vegetables, pea halm, &c. All these should be fermented, and applied, in the same manner as the common kinds of manure.

The following is a summary of the general rules to be observed in manuring and improving soils:—Never to use animal manure and quick-lime together, as the one will destroy the other. To use lime as a manure only in very sandy or peaty soils, or in soils abounding with sulphate of iron. To remember that rotten manure is considered to give solidity; and that unfermented manure, buried in trenching, has a tendency to lighten the soil. To dilute liquid manure from a dunghill with water, before applying it to growing plants; as otherwise, from the quantity of ammonia that it contains it will be apt to burn them. To cover and surround dunghills with earth during the process of fermentation, to absorb the nutritious gases, that would otherwise escape. To remember that the manure of cows and all animals that chew the cud, is cold and suited to a light soil; and that the manure of horses, pigs, and poultry is hot and suited to a firm soil: also that all manure, when well rotten, becomes cold in its nature, and should be treated accordingly. To remember that all mixed soils are more fertile than soils consisting only of one of the three primitive earths, viz. lime, sand, or clay; and never to forget that too much manure is quite as injurious to plants as too little.

Formation of hotbeds.—Though nearly all the kinds of manure which have been enumerated may be used occasionally for hotbeds, the only materials in common use in gardens, are stable manure, dead leaves, and tan. The first of these, which is by far the most general, consists partly of horse-dung, and partly of what gardeners call long litter, that is, straw moistened and discoloured, but not decayed. The manure is generally in this state, when it is purchased, or taken from the stable, for the purpose of making a hot-bed.

The necessary quantity of manure is procured at the rate of one cart load, or from twelve to fifteen large wheel-barrowfuls to every light, as the gardeners call the sashes of the frames, each light being about three feet wide; and this manure is laid in a heap to ferment. The heap should then be covered with earth to receive the gases evolved during fermentation, and earth laid round it to absorb the liquid manure that may drain from it. In about a week the earth may be removed, and the manure turned over with a dung-fork, and well shaken together; this operation being repeated two or three or more times, at intervals of two or three days, till the whole mass is become of one colour, and the straws are sufficiently decomposed to be torn to pieces with the fork.

The size of the hotbed must depend principally on the size of the frame which is to cover it; observing that the bed must be from six inches to a foot wider than the frame every way. The manure must then be spread in layers, each layer being beaten down with the back of the fork, till the bed is about three feet and a half high. The surface of the ground on which the hotbed is built, is generally raised about six inches above the general surface of the garden; and it is advisable to lay some earth round the bottom of the bed, nearly a foot wide, that it may receive the juices of the manure that will drain from the bed. As soon as the bed is made, the frame is put on and the sashes kept quite close, till a steam appears upon the glass, when the bed is considered in a fit state to be covered three or four inches deep with mould; observing, if the bed has settled unequally, to level the surface of the manure before covering it with earth. The seeds to be raised may either be sown in this earth, or in pots to be plunged in it.

The proper average heat for a hotbed intended to raise flower seeds, or to grow cucumbers, is 60°: but melons require a heat of 65° to grow in, and 75° to ripen their fruit. This heat should be taken in a morning, and does not include that of the sun in the middle of the day. When the heat of the bed becomes so great as to be in danger of injuring the plants, the obvious remedy is to give air by raising the glasses; and if this be not sufficient, the general heat of the bed must be lowered by making excavations in the dung from the sides, so as to reach nearly to the middle of the bed, and filling up these excavations with cold dung which has already undergone fermentation, or with leaves, turf, or any other similar material which will receive heat, but not increase it. When the heat of the bed falls down to 48° or lower, it should be raised, by applying on the outside fresh coatings of dung, grass, or leaves, which are called linings.

When hotbeds are made of spent tanner’s bark or decayed leaves, a kind of box or pit must be formed of bricks or boards, or even of layers of turf, or clay, and the tan or leaves filled in so as to make a bed. Where neatness is an object, this kind of bed is preferable to any other; but a common hotbed of stable manure may be made to look neat by thatching the outside with straw, or covering it with bast mats, pegged down to keep them close to the bed.