Part 5

The soil in which the Melon delights to grow, is one of a more compact texture than is usually regarded as applicable for the Cucumber: a suitable compost consists of the "top spit" from a loamy pasture, of a texture _rather adhesive_, and retaining the herbage and roots of the grass; this should be collected a few months before it is used, so that these vegetable substances may be in a _decaying_ state, and it should be broken roughly to pieces, but by no means sifted; to it, should be added, about one-fourth part of vegetable mould: the whole should be well incorporated, and, before using, should be placed in a situation where it may not be liable to become saturated by heavy rain; which would serve to destroy the free and open texture, which it is so desirable to retain.

In the application of moisture to the soil, the structure which is described in a previous chapter, will be found to present facilities, which peculiarly adapt it for the growth of these plants. In Persia, and the neighbouring countries, where the Melon is so successfully grown, the ground is irrigated by means of numerous channels, which, from the limitation of their exposed surface, are not peculiarly adapted to supply atmospheric moisture; but are yet sufficiently numerous to secure the perfect irrigation of the soil, within the reach of the roots. The tubes or shafts, represented at (_n_) in the sketch referred to above, are intended to communicate directly with a layer of coarse open material, extending entirely over the top of the tank, and beneath the soil; by means of these a supply of water should be poured beneath the soil, which will thus keep that portion immediately about the young roots, in a constant and complete state of saturation, by means of the steam which will arise, in consequence of the heat from the tank. A uniformly warm, and a thoroughly moist soil, will be thus easily secured, which are two important points in the growth of Persian Melons. It must be recollected that these conditions for supplying moisture, are recommended only during the time of growing the plants, and swelling the fruit; but as these latter approach their maturity, the degree of moisture must of course be gradually diminished.

In connection with this moistened and genial soil, the Melon has naturally the advantage also, of powerful sun heat, and intense light; and these are two conditions which it is indispensable should be supplied in artificial cultivation, as fully as they can possibly be obtained. It is by means of the moisture of the soil, that the plants are enabled to grow on rapidly and vigorously, because that moisture renders the food contained in the soil, soluble, and therefore available to the roots; but the elaboration and assimilation of this food depends on the degree of _light_ and _heat_ with which they are supplied: without these conditions, to convert the crude sap, by their united agency, into organic compounds, such as lignin, gum, starch, and sugar, and to induce their deposition, the fruit will indeed be formed--it will grow, and perhaps may even tempt the eye; but unless these chemical and vital changes have taken place in its constituent parts, the eye, as it frequently happens, will have been deceived; and instead of the palate being gratified by a mature and luscious fruit, it will find nothing but a tasteless mass of pulp. The plants, therefore, cannot, in our latitude, receive too intense a degree of solar heat, or of light.

The same cause which renders the natural atmosphere of the Melon countries elevated in temperature, renders it also comparatively dry; the sun drinks up the moisture which is deposited near the surface, or which may rise to that position; and by an exceedingly powerful influence effectually prevents the accumulation of moisture about the exposed parts of the plants. The atmosphere is nevertheless not in an arid state; the evaporation from a well-moistened soil effectually prevents this from being the case, but the excessive heat also as effectually and continually prevents an undue accumulation of moisture in the atmosphere. The application of this fact, to artificial practice, is plain; a less amount of moisture artificially applied, in comparison with the temperature, must be permitted, than when the cultivation of those plants is attempted whose natural habitats are less strongly featured in this respect.

Such considerations as these naturally force on us the conclusion, that it is vain to attempt the cultivation of this noble fruit, except during that portion of the year when the sun exerts his greatest power in our latitude. It is not because they cannot be induced to grow at any other period of the year, for the mere extension of vegetable tissue will go on, though the influence of the natural agents is but limited and feeble; but it is because maturity, perfect development, and, above all, the full assimilation of the sap, cannot take place sufficiently to ensure a good flavour in the fruit, except light and heat are not only unimpeded and constant, but powerful and united in their action.

CHAP. X.

CONCLUDING REMARKS.

I will here briefly recall attention to a most important point which the cultivator should continually keep in view: it is most important that he should _study Nature_; for if we may believe our senses, or place any confidence in overwhelming evidence, we may be certain that all the conditions we observe in a natural state of things, have been planned by an All-wise hand; and further, that a finite mind can never attempt with success, either to surpass or to dispense with any portion of that which an infinite being has ordained. "Order is Heaven's first law," and in whatever we may attempt to do, we shall not be wise, if we endeavour to effect our purpose by any means which may distort the fair proportions which unaided nature presents to our view. In cultivating plants, therefore, we should administer the conditions which are favourable to their growth and development, in somewhat the same proportions each to the other, in which they are naturally blended--not supplying one essential, in an undue manner, and, at the same time, neglecting others; for successful cultivation must ever depend upon the connection and influence of numerous circumstances upon each other, and can never be attained, unless these conditions are complied with, either designedly, or, as it often happens, by mere accident.

Another point which it is important to keep in view, is that instructions should be studied, rather than copied, in their application to practice. No instructions can be given that should be blindly and implicitly followed. The circumstances under which plants are placed are varying every day, and even every hour, and, to be successful, horticultural practice must be varied also. It must, however, be varied according to principle. But even what are regarded as established laws and principles should not be heedlessly followed; to be truly successful, a man must not only be a practical enthusiast and a keen theorist; he must also be a skilful experimentalist: his experiments and their results, if carefully watched, deduced, recorded, and studied, will serve to guide him for the future.

APPENDIX.

_On Heating, Ventilating or Aerating, and Covering._

Since the publication of the first edition of this work in 1844, the views expressed in the second chapter, with reference to structures best adapted for Cucumber culture in the winter season, have met with much corroborative support. Respecting the questions of heating, ventilation, and covering, a few more words may be added.

I have before recommended hot water tanks for supplying bottom heat, with attached pipes for the circulation of hot water to warm the atmosphere. I can see no reason for recommending any other arrangement now; for the experience of successive years goes to show that hot water, applied on sound principles, is, above all other means of heating, effective in its operation; and as to the question of expense, raised as an objection to it by some, it is sufficient to say, that, although one hot water apparatus may be fitted up in an expensive manner, another may be rendered perfectly successful in its operation, at the same time that it is extremely simple in its arrangements, and correspondingly inexpensive in its cost.

A seeming error in the engraving, at p. 18, has been pointed out to me. In the description of the sketch it is stated that, "a series of pipes attached to the same boiler [which heats the tank] would supply the requisite heat to the atmosphere." The sketch itself shows these pipes to be considerably above the level of the water in the tank, and where they could not, consistently with the other arrangements, be thus employed. This may be explained thus:--the sketch was introduced rather for the purpose of illustrating certain proposed arrangements, as regards bottom heat and ventilation, than as furnishing an exact and detailed design for a model structure; and thus it happened that the pipes were merely shown to be placed at the front part of the house, to indicate that this was their proper relative position. There would be no practical difficulty in placing the pipes lower down, and nearly close to the front wall, so as to admit of the proposed connection; all that would be required to effect this, being to fix the slab, on which they rest--and which prevents the air from rushing upwards into the atmosphere of the house at this point--in a sloping position, instead of a horizontal one.

The principle involved in the plan proposed for aëration or ventilation, is no doubt a sound one; and though the plan which is more particularly described may be modified and varied, yet it is believed to be efficient for its intended purpose.

There can be no doubt that the admission of cold air to a structure in which tender plants are being forced, either during winter or early spring, is materially hurtful to the plants, in proportion to the tenderness of their constitution; and the Cucumber being, under those circumstances, a plant of a very tender and delicate nature, is especially susceptible of harm from this source. As a consequence resulting from this fact, there can be little hesitation in affirming that whatever fresh or external air it may be necessary to admit, during the period referred to, should be warmed before it reaches the plants, and in being warmed not burned, but supplied with the additional moisture its increased heat capacitates it to take up, and which, to be congenial to vegetation, it requires. This is provided for by the plan already recommended, where the cold air is made to pass through the tank containing the heated water which warms the soil. By a perfectly practicable modification of this arrangement, not only may this result be secured, but also the continual circulation of the internal atmosphere may at pleasure be assisted and accelerated, during the time when it might not be necessary to admit fresh air. This would be an additional advantage. The arrangement proposed to effect this, is to conduct the cold external air through a heated chamber containing the tanks--these latter being covered, but also admitting of being opened to any extent to supply moisture or steam in the proportion required. The cold air, after passing upwards through the chamber, escapes at the front of the house, and ascends to the upper part of the house, from whence it finds its way downwards near the back wall, and there again enters the chamber, through openings provided for the purpose. The circulation of the internal atmosphere would be thus facilitated and accelerated, even without the admission of any current of external air, for, of course, there is more or less of this kind of movement going on in the atmosphere, wherever and in whatever form a source of artificial heat is present. Another mode of combining internal atmospheric motion, with ventilation, and by which the cold air is warmed before it reaches the plants, has been practised with very marked success, in a vinery at Park-hill, Streatham, Surrey; and I have described it in the _Journal of the Horticultural Society_[1] as follows:--"This plan consists in passing a zinc pipe, thickly perforated with small holes, from end to end of the vinery, and exactly beneath the range of hot water pipes, which heat the structure. In the outer [end] wall, communicating with this perforated pipe by means of a kind of broad funnel, a register valve is fixed, by which the admission of air can be regulated with the utmost nicety, or the supply be shut off altogether: this valve is fixed a little below the level of the perforated pipe. The action of this contrivance was evident enough from the motion communicated to the foliage of the vines; and its effects were apparent in the unusually healthy and vigorous appearance they bore, until their period of ripening. In this case, sufficient moisture was kept up by syringing the walls and pipes, wetting the pathway, and by the use of evaporating troughs, placed on the metal pipes, and kept constantly filled with water."

In another communication published in the work already quoted,[2] after alluding to the now well-known garden truism, that a comparatively low night temperature is indispensable to the maintenance of vigorous growth in plants of all kinds, I have advocated a more extended adoption of the practice of night covering hot houses, as a means of permitting the low night temperature required, and at the same time securing the plants against the extreme cold to which they would thus be sometimes liable. From the changeable nature of our climate, there is some difficulty in apportioning the degree of applied heat, so as to suit exactly the requirements of the plants in these respects; and it is especially difficult to maintain with certainty the low degree of night temperature which would be desirable, and at the same time avoid risking the safety of the plants, through a sudden declension of the temperature of the exterior air. At present this difficulty has to be met by extraordinary care on the part of the gardener, and often by serious encroachments on his proper time for study and for rest: even then sometimes without success. This end would be much more effectually and certainly secured by a _complete system_ of covering hot-houses and forcing-houses; and this plan would secure the further advantage of avoiding the undue stimulation of the plants by a then unnecessary amount of heat, applied solely to prevent the very evil which covering also prevents, namely, the risk of excessive cold during the night.

The principle upon which a covering acts most efficiently, is that of enclosing a complete body or stratum of air exterior to the glass, this body of air being entirely shut away from the surrounding outer atmosphere. Air being a bad conductor of heat, the warmth of the interior is by this means prevented from passing to the exterior atmosphere; or, in other words, the exterior atmosphere, being prevented from coming in contact with the glass, cannot absorb from the interior any material proportion of its heat. To secure this advantage, however, the coverings _must_ be kept from contact with the glass, and they should extend on every side where the structure is formed of materials which readily conduct heat--such as glass or iron. The coverings should in fact form neither more nor less than _a close outer case_.

One point connected with the application of these coverings, which I consider would constitute an improvement, and which, as far as I am aware, has never been acted on, is that of having them to fit so accurately as to exclude the external air (a matter of no difficulty in the degree required), and then to have a series of ventilators provided, to stand open during the night, whereby an interchange of the atmospheric volume would take place throughout the night, without exposing the plants to contact with cold air. The stagnation of the internal atmosphere would thus be prevented, in consequence of the interior air and the air between the glass and the covering being of different degrees of density, owing to their being differently charged with heat. By this plan, therefore, I conceive that direct benefit would accrue to the plants; and it would also materially assist in preserving that cooler--but not cold--night temperature, which the fear of injury from frost prevents from being more fully realised in ordinary cases.

The annexed diagram represents one of the many ways in which this idea might be carried into practice. It will be understood that, as here shown, the side shutters and end shutters (the latter not indicated), fit into grooves, the upper groove being attached to iron pins, and thus fixed at a proper distance from the building, without obstructing the passage of air along the enclosed space; and that on the lower side being so fixed as to exclude the external air in that direction. The top or roof shutters also run into a groove along the ridge of the roof, and at the lower end fix close down to the top of the side shutters, fastening with a button. Each of the shutters should have a projecting fillet fixed on one side, so as to shut close over the adjoining one. The shutters themselves should of course be made of light frame-work, strengthened where necessary, with small iron rods. The material used for covering them may be the asphalte felt, now manufactured extensively for roofing purposes, or strong brown paper, coated with tar; the latter is used extensively in Germany for this purpose, and is found to be very durable and cheap; it is there even preferred to every other material.

Though the covering of hot-houses has been already practised in some cases, I am not aware of any one having adopted a close covering with the view to facilitate ventilation or aëration during the night. It appears to me that the circulation of air, secured by the means here proposed, would have much influence in excluding cold, whilst at the same time it would prevent the interior from becoming too warm and close.

_On Transplanting and the use of Turf Pots._

I have, at p. 26, given what appear to me to be some of the principal reasons against the practice of transplanting, or planting out, Cucumber and other plants. When this is done after any quantity of roots are produced, some injury or check must be sustained during the process; and checks of this kind are opposed to the realisation of the greatest results within the shortest period, which of course is the great object in view. Where it is inconvenient to plant the seeds in the places the plants are intended to occupy, or to put out the young plants during the earliest period of their development, or where propagation by cuttings or layers, is adopted, and the plants of course have to be potted separately, so as to be in a removable state, the following simple plan may be adopted, and will be found to combine all the advantages and conveniences attending the use of pots, with the avoidance of the evils of transplantation, &c. The plan referred to, consists in the employment of turf or peat, so contrived as to supply the place of pots, and which of course at the time of planting is simply placed, along with the plant it contains, at once into the soil, without in the least disturbing the roots, which, growing through the substance of the turf, extend beyond it in all directions into the free soil provided for them. These turf pots are made of spongy, fibrous turf--whether loamy or peaty is not material, provided it is full of fibre, so as to admit of being readily traversed by the roots. The grassy surface is evenly removed, and the under-turves are cut three or four inches in thickness, and are then divided into squares of about three inches across. The centre of each of these little squares is taken out by means of an iron scoop, such as that represented in the annexed sketch; and this is then filled up with soil, and the plant, or seed, or cutting, or layer, inserted as if it were into an ordinary flower pot. It will be obvious that by this plan, every plant is independent and perfectly removable--thus securing the convenience of sowing or planting and rearing the plants in pots during their earliest stages: on the other hand, at the time of planting out permanently, the plant, turf, and all being set carefully into the soil, no check is sustained, because the roots remain undisturbed, and may, as they advance, penetrate through the turf into the prepared soil which surrounds them; in this way the advantages of sowing or planting at the very first in the position the plants are intended to occupy permanently, are secured.

This plan of sowing seeds, or of planting young plants intended for transplantation, into pots made of turf, is not only applicable to cucumbers, but might be very extensively adopted in the case of annuals and half hardy plants raised in frames, during the spring, in large quantities for the flower garden. In these cases, however, as the quantity that could be reared within a given space would be an object, the turves should be as small as possible in their lateral dimensions--a bore of two inches and a half, with half an inch on each side, thus making the diameter three inches and a half, would be found convenient in this respect. For cucumbers, however, or when the plan was applied to any special object, a larger size might be employed, which would allow of the plants attaining a larger size before it would be necessary to place them in their permanent positions.

_On Watering the Soil._