ON THE STRUCTURES ADAPTED FOR THE GROWTH OF CUCUMBERS.

I will preface the following remarks on the structures adapted for the growth of Cucumbers, by stating, that a forcing house, a pit, and a common frame, present the means of bringing this fruit to its perfection, equally, one with the other, provided that a course of cultivation suitable to the structure, is followed out; the comparative merits of each, depend not so much on the nature of the results which may be obtained by adopting them, as on the facilities they afford for the attainment of those results.

The use of the common frame, and the ordinary hotbed of fermenting manure, nevertheless involves these difficulties:—the fermentation is liable to become excessive, and that in a very rapid manner, and also to decline as rapidly; the heat, when declining, cannot be speedily restored in unpropitious weather; it is materially checked in its action, by that particular state of the weather, which renders its efficient action most essential; it involves almost an infinitude of labour; and after all, it is uncertain in its action: when such difficulties as these, are overcome, Cucumbers can be grown to perfection, on dung beds, assisted by the common garden frame and sash.

The brick pit, when heated by fermenting manure, presents difficulties of the same nature with the preceeding, though in a less powerful degree: but when these structures are heated by means of hot water, in any of its various modes of application, there need be no irregularity, nor uncertainty in its action; because the supply of the elements of vegetable developement, and of the agents by whose aid they are applied, may, to a very great extent, go on uninterruptedly.

A forcing house, whilst it secures all the advantages which are presented by a pit, combines with these, some important points which are peculiarly its own: by adopting a pit, we provide a structure of which Cucumbers manifest their approval, by thriving equally as well as in their more ancient location on a dung bed; but further than this, a pit enables us to dispense with much of the labour, and all the filth, and the uncertainty which are consequent on the use of fermenting manure as a means of keeping up the temperature in which they are grown. In a small forcing house, besides these advantages being secured, all the operations of care and culture, can be performed just when they become necessary, without exposing the tender foliage of plants which have been submitted to an artificially elevated temperature, to the chilling influence of cold air, which is admitted whenever the sashes of an ordinary frame or of a pit, are opened, in order to bestow these necessary attentions. It may be urged that a dung bed has still the advantage, on the ground of economy; but when a fair calculation is made of labour and loss or anxiety on the one hand, and of duration on the other, such an assumption, will be quite untenable. Neatness, convenience, certainty, and economy, are the principal points of advantage which are gained by the adoption of pits heated by means of hot water, over those of a structure, depending for its supply of heat, on the aid of fermenting masses; whilst the attainment of a still greater degree both of convenience, and of certainty, which may be secured by cultivation in forcing houses, point out at once the advantages which render such houses, preferable to pits.

The application of the gutter system of heating, was not long since thought to be an improvement of great importance, and there can be no question but that it affords a means of regulating the moisture of the atmosphere of hothouses, in conjunction with the temperature, which prior to its introduction had not been attained; and as such, it is worthy of extensive adoption: it requires however some judgement in its adaptation to particular structures, and to render, it suitable, to effect any particular object for which it may be employed.

The tank system as a means of applying bottom heat, employed either in conjunction with the gutters, or with ordinary piping, to supply heat to the atmosphere, is the most important advance which has hitherto been made towards supplying the wants of those plants, which require such peculiar aid; and with reference to the Cucumber, it may be regarded as furnishing a new era in its cultivation.

The importance of bottom heat in the culture of tender plants, has always been well known by its practical effects. The mean temperature of the soil, at a slight distance below the surface, is universally above that of the superincumbent air; and consequently some degree of bottom heat is always supplied to plants, in a state of nature. Naturally, by means of subterraneous heat, and also by the absorption of the sun’s rays during the time they are forcibly directed towards the earth, it possesses the means whereby any material degree of cold at the roots of plants is prevented; and when the soil is acted on by the unveiled sun of an eastern sky, we cannot but feel certain, that even a considerable amount of heat must be experienced: hence arises the importance of taking advantage of every ray of sun which our climate affords, when the culture of the Cucumber, or of any native of warmer latitudes, is attempted out of doors in this country; and also of using every possibly available means of increasing rather than diminishing the temperature of the soil: and hence too, in forcing not only the Cucumber, but also every other plant which requires to be submitted to a confined atmosphere, and an elevated temperature, arises the necessity of providing such a degree of warmth at the root, as may tend to keep its vital powers in a vigorous state of action; it will effect this, by acting in conjunction with moisture, as a solvent of the food which is primarily contained in the soil in a solid form, but can only be taken up by the capillary action of the spongioles of the roots, when converted into a fluid state. The science of Chemistry has taught us that the ingredients composing the soil, act on, and dissolve, and combine with each other in various ways, sometimes being simply dissolved and held in solution, and at other times, entering into new combinations, and forming new compounds; but in all cases, the natural agents, heat and moisture, are necessary to produce these results, and to present to the tender roots of plants, food so duly prepared, as to be fit for their assimilation. Warmth in the soil, acts beneficially also, by preventing the sudden or undue interruption of the excitability of plants growing in it, which would be likely to result from the lowering of the temperature of the plants by evaporation, were it not for the action of the antagonist force, existing in and exercised by the heated soil, which heat, is communicated to, and absorbed by the plants.

It may be regarded as an established and universal rule, that all plants require the soil, and the atmosphere in which they are cultivated, to correspond with the natural circumstances under which they flourish; and as it has been repeatedly ascertained that the soil is naturally a degree or two above the temperature of the atmosphere, we have certain and unerring data for the application of bottom heat, and no more powerful evidence than this can be desired, to condemn at once the application of a very powerful degree of heat, at the roots of plants.

The importance of bottom heat in the culture of tender plants, being a practical fact established beyond question, another consideration arises as to the best means of producing it, and of regulating its application. Various substances and materials have been submitted to a process of fermentation, and so employed to effect it: stable manure, tanner’s bark, and the leaves of trees, are among the principal of these materials, and either of them will supply just what the plants require, as truly as these wants can be supplied by any other means; but from their very nature, they are violent, and fluctuating, and ephemeral in their action, and setting aside the labour which the employment of them necessarily involves, we have in these particulars, the special points in which the tank system of applying bottom heat far excels them: it is uniform, and constant, in its action; there need be no apprehension of the soil becoming overheated, for the source whence it derives its warmth ought never to boil; neither need there be any fear of its decline, or of a want of power, for when once thoroughly heated, a body of water will part with it in such a manner, that a very little attention to the fire, and a very little expenditure of fuel, will maintain its temperature for an almost incredible length of time; and as to power, it never should for a moment form a question, because a powerful degree of bottom heat ought never to be applied: a close attention for one or two hours during the twenty four which form a day, will maintain any apparatus in an effective state of action, if it is properly erected. How different is this, to what has been in days now past! when in rigorous weather, with the heat of his dung bed declining, the cultivator knew that at the peril of his crop, he scarcely dared to attempt to revive it, without involving a more serious because an accelerated evil; at any rate, if at an immense sacrifice of labour, his dung casings were replenished piece by piece, he knew too well, that often many days would elapse, before their action would be efficient and satisfactory, unless indeed an unlimited supply of materials, were in a constant state of preparation. By means of the tank, a fire could be lighted up, and the required effect produced in as many hours, as days would have been formerly required.

What has been already advanced, tends to the conclusion, that small forcing houses are preferable, and in the end more economical than pits and dung beds; and that the tank as a means of supplying bottom heat, is preferable to the use of fermenting materials; because the results in each case, are more perfectly under controul. Whilst on this part of the subject, I may be allowed to mention an error which is somewhat prevalent: We frequently hear of the humid nature of the heat given off by hot water pipes, in comparison with that derived from such appliances, as a flue; it is not unfrequently asserted, that the heat thus derived is so moist, so genial, so peculiarly adapted to plants: there can be no doubt but that the heat thus obtained is infinitely preferable to that obtained through the medium of flues, generally speaking; but its superiority consists rather in its purity, its freeness from noxious gasses, than in its possessing a greater degree of moisture. Heat—that is—caloric, is the same, whatever may be the medium by which it may be conducted; and in the case of hot water pipes, they give off that which has been conducted to them by the water, directly from the fire, the water acting as a mere conductor; it is difficult to conceive any thing more thoroughly devoid of moisture than the heat thus communicated: let any one who doubts this, place a damp cloth on a series of hot water pipes when in action, and the result will soon work conviction. With these general remarks, I will proceed to describe the kind of structure which I regard as being peculiarly adapted to the growth of Cucumbers; and notice some of the conditions which it is necessary to keep in view: the engraving on the next page, represents such a structure.

The aspect of the Cucumber house, should be nearly S.S.E; or in other words—it should be so regulated between the points south and east, that whilst the rays of the sun will be admitted as fully and as early as possible in the morning, there may be no obstruction offered to their more powerful action as that body approaches the meridian. In the growth of all tender plants, light and sun heat are required during the winter months as well as in summer, and there can be no greater error as regards the erection of structures devoted to such purposes, than to provide for their admitting the direct rays of the sun in the earlier part of the day, at the expense of refracting and thereby weakening, to a greater degree than is really unavoidable, the power of the noon-tide rays of that invigorating and life-sustaining agent: during the summer months, though plants then require both light and sun heat, yet the case is different; the sun’s rays have then much greater power, and it is found that their influence is sufficient, without at all times admitting them directly on the plants growing in these artificial atmospheres.

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The position of the Cucumber house, with reference to the ground line, must be determined by local circumstances; if the situation and sub-soil be dry, it may be carried below the surface in the manner represented in the annexed engraving, of which (a) is the ground line, (b) the pathway, and (c) the lowest point excavated: the same course may be adopted if the soil, though not naturally so dry as this, can be rendered so by thorough drainage; but when the ground does not admit of perfect drainage, the structure must be sufficiently elevated to avoid the risk of injury from the dampness of the locality.

The angle of elevation is not, as it is sometimes asserted to be, a point of indifference, though mathematical accuracy is certainly by no means required: in the annexed engraving, the angle of the roof is about 55°, this provides for the admission of the sun’s rays in the winter months, when his position is comparatively low in the horizon, to a much greater extent than could take place if a more ordinary slope were adopted. A still more elevated pitch would doubtless effect this object in a still more perfect manner; but would not be equally applicable to the requirements from a permanent structure, which would be wanted for summer as well as winter use.

A reference to the sketch, will at once shew the general nature of the internal arrangements. There should be a tank (d) supported by brick piers (p) in which a circulation of heated water would supply a genial warmth to the soil above, and to the roots of the plants growing in the soil; this tank should be heated by a small boiler, conveniently placed with reference to adjacent arrangements; a series of iron pipes (e) attached to the same boiler, would supply the requisite heat to the atmosphere. It may perhaps be thought that the application of the gutter system of heating would in this case be preferable; but as there would be a perfect command of moisture, as will be explained further on, it is desirable to have dry heat also, under controul, and this can be better effected by means of the pipes than by adopting the gutter plan of heating. I cannot in this place forbear protesting against the limited surface of piping generally employed in heating plant structures; what is thought to be just enough to maintain a given temperature, is usually after minute calculation, the quantity which is made use of, and the consequence is, that under adverse circumstances, the apparatus is necessarily worked at its highest pitch; and I believe that the application of heat in this form, whether it be by means of an hot water apparatus, or by a common flue, is most inimical to the plants submitted thereto. The admission of air, is a point which as far as I am aware, has never been effected in the manner represented in the sketch: it would be thus effected;—a series of apertures (f) should be provided at intervals along the front wall, which would externally be closed by small sliding shutters, and would communicate internally with a chamber (g) formed between the front wall and the side of the tank; this chamber would also communicate, by a series of openings, (h) with the interior space above the water in the tank, and from this space, through the covering of the tank, tubes (m), also placed at intervals, would be carried up through the soil, close to the side of the wall; these tubes should be furnished with caps or valves, so as so admit of the communication being stopped at any time. In applying this to the admission of air, we must not loose sight of a series of ventilators, (i), placed in the back wall of the house, which are of precisely the same nature and construction as the apertures (f), already spoken of. I shall have occasion hereafter, to notice the admission of air, but it will be well in this place, to explain the action of the plan proposed for that purpose: when it is judged that a change of the internal volume of air is requisite, the ventilators (i) are to be opened, which admits of a portion of the rarified air to pass off; the ventilators (f) are also to be opened, and by means of the action of these ventilators on each other, a portion of external air is taken in; this enters the chamber (g), which is warmed by its contiguity to the tank, and here becomes partially rarified, and rises to the top of the chamber; the apertures (h) admit it to the interior of the tank, where it becomes not only thoroughly warmed, but also imbibes a degree of moisture proportionate to the degree in which it becomes heated, and thence it enters the house by the tubes or shafts already spoken of. The advantages of warming and moistening the air thus admitted, are very important ones; for when either a cold or dry state, of the atmosphere prevails, its influence is very injurious to plants in these confined situations: cold raw air, when it comes in contact with the tender foliage of the plants, has the effect of chilling the sap in its progress through their tissue, and thus lessening their excitability, when it should be increased; whilst dry air acts as an incessant drain upon the vegetable juices, which it abstracts through the stomates and pores of the leaves and stems. When cold air is admitted to any position where it can unite with caloric, and not in an equal ratio with moisture, it necessarily becomes arid, and in that state it eagerly combines with moisture in any form with which it can come in contact therewith; and consequently if cold air is admitted to a plant structure, where it can have the means of combining with heat, faster than with moisture, it would be brought into this arid state, and would supply its voracious appetite, by abstracting the juices of the plant. It is a very important question how far this state of things is connected with many of the diseases as they are called, to which plants are subject; for my own part, I believe it to have a very considerable influence in the production of many of them. A shallow bed of soil (k), is all that would be required; for in the winter season, there is nothing gained by encouraging a very luxuriant and gross state of growth: the composition of this soil will be noticed hereafter: beneath it, and resting on the top of the tank, should be placed a layer of coarse open rubble, not less than six inches in thickness; and among this rubble by means of tubes (n), placed at intervals along the bed, I would occasionally pour considerable quantities of water, in order to maintain a due regulation of moisture in, and throughout the soil, among which the vapour arising from the water would ultimately rise. Beneath the tank a space (o), might be provided, which would serve admirably either for the cultivation of Mushrooms, or the forcing of Rhubarb, or Sea Kale. Transverse partitions should be introduced into the bed of soil, so as to divide the roots of each plant from those of its neighbours: this arrangement will admit of a complete succession of plants being maintained, by the removal of those which have become old and debilitated, and the substitution of young and vigorous ones; and this obstruction of the roots, will not be injurious, for the Cucumber does not by any means require to be permitted to extend its roots at random, but will readily submit itself to any rational regimen, with regard to the area from whence it is permitted to extract its food. A portion of soil sufficient to support one or two plants, could by this arrangement be renewed as occasion might require, and the roots of the contiguous plants would suffer no injury from the operation. The pathway of the house, should be paved so as to admit of its being occasionally washed and cleansed.

It will be found to be highly economical in reference to the consumption of fuel, to provide the structure with the means of being covered at night. Shutters of light frame-work, covered with any waterproof material, would be found to answer the purpose admirably; they should be elevated a few inches from the surface of the glass, and they should be arranged so as to confine a body of air, which acting as a very slow conductor of heat, would serve to prevent that incessant drain upon the temperature of the internal atmosphere, which takes place when the material employed is in contact with the glass, as well as when coverings are altogether absent. This would not be the only advantage, for as the covering would to a great extent prevent the radiation of heat from the internal atmosphere, so would it also prevent the necessity of the application of so powerful a degree of fire heat at night; and thus the plants would be permitted to enjoy that natural season of repose so essential to their well being, instead of being forced into growth by reason of a high temperature kept up, solely for the purpose of obviating the external cold.

Chap. III.