The various expedients for obtaining the necessary degree of heat, are, first, the most simple method of a stove, with its flue passing through or round the floor of the house, and this for warming the air within; but in this case, as the roots of the plants do not sufficiently, it is supposed, receive the proper degree of heat, various fermenting substances, as recent stable-yard dung, tanners’ bark, oak and other leaves of trees, &c. are formed into beds, on which the compost of earth is placed, as in hot-bed frames, or in which the pots containing the plants are placed, or plunged, as in a hot-house. To obtain the same effect, borders within houses are formed for the roots, having an excavated heat-chamber beneath, supplied by simple stove flues, or from the fermenting substances above named, or from steam admitted for the purpose. This mode of supplying an equal degree of heat to the roots, as well as to the leaves and branches of a plant, is plausible, and cannot be far wrong, because it has been attended with success: but there is, perhaps, more attributed to it than it deserves, because the region or stratum of the soil, which is naturally occupied by roots, differs, in respect of temperature, much less over the whole surface of our globe, than is commonly imagined. The heat of the air in different latitudes ranges from several degrees below zero to 110 degrees of Fahrenheit’s scale; but the temperature of the earth eighteen inches below the surface, it is probable, does not vary more than ten or fifteen. In England spring water varies only two degrees, viz. from 42 degrees in summer to 40 degrees in winter; and the effects of our hardest frosts very rarely penetrate deeper than nine inches; but it is necessary to observe, that, in such cases, as well as in hotbeds, we force as well as defend; and probably, by such mode of applying heat and moisture, nutritious gases may be communicated, which may be no small advantage. Besides, the atmosphere of the house can (as is done) be impregnated with the same qualities and degrees of heat and humidity [p274] (a most necessary accompaniment[51],) which may be generated below.
Light is a most potent agent in the maturation of vegetables: united with a moderate degree of cold, it is much more effectual in progressive vegetation, than the necessary degree of heat with darkness. Exposure to light is indispensable to plants: and, therefore, our glass cases are formed to admit as much as possible. Within these few years, the endeavour to gain an accession of light by reducing the dimensions of the wooden scantling of hot houses suggested the idea of metallic frames; and for the concentration of the sun’s rays, horizontal as well as vertical curvilinear roofs have been constructed. Lightness to the eye, durability, imperceptible expansion, and glazed with panes, cut like segments of circles, to facilitate the passing off of condensed water, with complete command of ventilation, are an assemblage of properties, always as desirable as necessary; and as they may be cast in the most elegant forms, and protected by paint, they add greatly to the ornament of the garden. Beautiful as these buildings are, some little disappointment has taken place respecting them: it has been experienced, that the intensity of the sun’s light, or heat, has been found detrimental to the tender inmates, and that shading is as necessary in bright, as light is in cloudy weather. Certain it is, that in the winter season, when light and heat are most desirable, no fear need be entertained from this circumstance; and it ought to be considered, that in our summer, we have at least, daily, four hours more sun than intertropical plants have at home: of course, they have less time for their evening’s repose, (which all plants more or less require); besides, it should be thought of, that all plants are not equally formed to sustain such a blaze of light; “some affect the sun and some the shade;” such as the pine-apple[52], and orange, which require “a warm [p275] shade;” and perhaps all plants which present a large reflecting surface of foliage to the sun, are content with a smaller share of his direct rays. These observations attended to, sun-shades may be applied for occasional use, and with the plants at a proper distance from the glass, will certainly secure them from all the inconvenience of such buildings, while none of the advantages are lost.
The kitchen-garden range of buildings includes pine-stoves, vineries, houses for peaches, and nectarines, figs, and cherries, hot-walls, pits for succession pines, melons, cucumbers; besides store pits for roots, tender vegetables, salading, &c., as well as frames for many purposes of cultivation. Mushrooms are usually raised in sheds behind the houses. The hot-houses are also used for growing early culinary vegetables, and small fruits in pots.
[To be continued.]
[48] The cocoa palm is rather a gigantic herb than a tree: the stem rises to a great height, of a strongly tough fibrous substance, but never so indurated as timber, though it is used in the construction of houses. It has no branches; but is crowned with from five to seven ample compound leaves, forming an umbrella-like head. The spatha issues from the centre, and soon falls pendent between and below the footstalks of the leaves, where it flowers and ripens the fruit. The nut is enveloped in a thick brown fibrous husk, which opens to shed it when fully ripe. The nut, when opened, yields two liquids, which are nutritious, and accounted delicacies: the first is the milk which runs out; the next is the cream which is procured by being scooped off the kernel with a spoon: this is of thick consistence, and much resembles the cream of milk. After these remains the perfectly-formed layer of kernel attached to the shell, and which is used along with the liquids as an article of food. But another most pleasant beverage, called toddy, is obtained from this palm, and which constitutes the chief value of the plant. The fruit is sacrificed to procure this; soon as the frond becomes pendent, the extremity is cut off, and a narrow-necked vessel is slung thereto to receive the streaming sap. This, both before and after being fermented, is an agreeable and refreshing drink. It also yields an ardent spirit by distillation, but of which the natives deny themselves the use.
[49] In Martin’s painting of the Paphian Bower, though a fine composition, the roots of the tree, on the left of the foreground, are too much out of the ground. The accidental exposure of roots on the bank of a stream, or high-road, and their buttress-like departure from the trunk, are legitimate objects for the pencil; but their ramifications pourtrayed on the surface of the ground, is as ridiculous as unnatural.
[50] It is said that many of the Caroon cherries brought to Covent-garden market, are bought up for the purpose of colouring wine on the Continent.
[51] The admission of humidity into forcing-houses is attended by the most salutary consequences: it counteracts the bad effects of fire-heat, and is inimical to many insects. For this purpose, a steam-supplying apparatus is added to the best-constructed hot-houses, productive of the greatest advantages.
[52] It has long been observed by gardeners, that the pine-apple always does best in forcing-pits, merely from the circumstance of there being more shade.