The different modes of cultivating the pine-apple / From its first introduction into Europe to the late improvements of T.A. Knight, esq.

by J. C. Loudon

The house was again stocked with plants, which Mr. Knight, in a paper read to the Horticultural Society, in November last (1821), stated to be in a most thriving condition; and a friend of ours who had made an extensive gardening tour in the North and West of England, and who saw the Pine plants at Downton Castle, also in November, declares they appeared the most magnificent he had seen on his journey; “the plants,” he says, “were stocky, and the leaves long, broad, and green; the largest were in pots fourteen inches in diameter, and their leaves reached to the glass.”

In the paper alluded to, Mr. Knight goes on to say, “I possess more than sufficient evidence to enable me to assert with confidence, that, in the culture of the Pine Apple, the bark bed, or other hot-bed, if the plants be plunged into it, is worse than useless, after the scions, or crowns, have emitted roots; and that the Pine Apple, when treated in the manner I have recommended, is a fruit of most extremely easy culture.

“It is contended, in favour of the bark-bed, that the soil in inter-tropical climates is warm, and that the bark-bed does no more than nature does in the native climate of the Pine Apple. And if the bark-bed could be made to give a steady temperature of about ten degrees below that of the day temperature of the air in the stove, I readily admit that Pine plants would thrive better in a compost of that temperature, than in a colder. But the temperature of the bark-bed is constantly subject to excess, and defect, and I contend, and can prove, that the above-mentioned temperature is very nearly given in my stove. For the temperature of the day being about 90° or 95°, and that of the night 70°, the mould in the pots will necessarily acquire nearly the intermediate temperature of 80°. It is true, that two disturbing causes are in action; the evaporation from the mould, and porous surface of the pots, and the radiant heat of the sun. But these causes operate in opposition to each other, and probably nearly negative the operation of each other, as far as respects the temperature of the mould in the pots.

“A very great number of gardeners have within the last twelve months visited my garden. Some of these were at once convinced of the advantages of the mode of culture which they saw; others have paid a second, or third visit; but every one has ultimately declared himself a zealous convert. I have never yet seen plants of the same age equally strong, nor any producing fruit better, nor indeed so well swelled; nor any equal in richness and flavour. But I have never taken off, nor shortened a root, nor taken any other measures to retard the period of fructification, with the prospect of obtaining larger fruit; and my plants have almost always showed fruit when fourteen or fifteen months old, though propagated from small and young suckers, or crowns. A great part of my Queen Pines (I have hitherto scarcely ever cultivated any other varieties) have, however, at that age, shown fruit with eight, and some with nine rows of pips; and I often see fruit of less weight growing upon plants of nearly double that age. Whether I shall be able to retard the period of fructification, or not, I have yet to learn; but I believe, I shall succeed by crowding my plants close together, so that each may receive less light.

“Pine plants will, however, grow perfectly well in composts of different kinds; but I have found that they have succeeded best when the materials have been fresh, and retaining their organic form, particularly if the pots be large, relatively to the size of the plants, which, I think, they always ought to be, for the mode of culture recommended. I have used, with advantage, the haulm of beans cut into lengths of about an inch.

“Very contrary to the conclusions which I should have been led to draw from writings upon the culture of the Pine Apple, I have constantly found that my plants succeed best in the part of my house where the flue first enters, and where the temperature is very high, varying from about 85° to 105°, and the air excessively dry. I have pointed out this circumstance to every gardener, whom I have seen in my house, and all have expressed their astonishment at the circumstance. I expected that this excess of heat would have occasioned the plants to show fruit prematurely, but this has not occurred in a single instance. What would be the quality of the fruit, if it were to be ripened in so high a temperature, I have not yet had an opportunity of knowing.

“In raising young plants, I have deviated from the ordinary mode of practice by breaking off the suckers when very young; that is, when they are not more than four or five inches long. The fruit is much benefited by their absence; and the cuttings, if placed very close together in a hot-bed, are made to emit roots with little trouble, and afford better plants than they do when they are suffered to remain long upon the parent stem. When the whole are removed at an early period, one or more very strong suckers usually spring out below the level of the soil; and from these, suffering only one to remain attached to the parent stem, and preserving the roots as entire as possible, I have propagated with much advantage, and have obtained plants which showed fruit strongly at seven months, dating from the period at which the sucker appeared, like a strong head of asparagus, at the surface of the soil.

“The success of my experiments, in the first house which I erected, (and to which the foregoing account exclusively refers,) led me to erect another house ([figs. 18.] [19.] and [20.]) in the summer of 1829. In this I attempted to obtain the greatest possible influence of light, and command of solar heat; inferring, from having observed Pine Apples to ripen tolerably well with very little light, that I should be able to ripen them in perfection late in the autumn, and early in the spring, particularly at the latter period, in which, alone, I set a very high value upon the species of fruit. The height of the back wall ([fig. 20.]) of this house is eight feet six inches, and that of the front wall is one foot six inches, and its breadth ten feet, inside measure, with an iron curvilinear roof, ([fig. 18.]) of the kind of bar invented by Mr. Loudon, of Bayswater. This house is fifty feet long, ([fig. 19.]) and capable of containing two hundred fruiting Pine plants. The curvature of the roof rises just one foot in twelve. The glass is laid in a composition of two parts white lead, with oil, and three of flint sand, and the overlaps of the glass are closely filled with the same material. It is, consequently, very nearly air-tight; and no means are given for the air to enter, or escape, except by apertures immediately under the copings of the front and back wall, (a and b, [fig. 20.]) which can be efficiently closed at any time. It is, consequently, an instrument of very great power, and requiring, of course, much attention to ventilation: of which I had rather a lamentable proof in the last spring, when my plants were all burned, and spoiled in a few hours; the person who had the care of them having left them in a bright day closely shut up. The fault was not, however, in any degree in the house, for the plants were, previously, much the strongest, and the best I ever saw; and I believe, they would have afforded most beautiful fruit. I furnished the house again with plants as expeditiously as I could, chiefly in July; and I have since kept the temperature of it nearly between 70° and 95°, with a wish to make the plants show fruit and blossom in the present month (October.) In this, I have in part succeeded, though many of my plants have flowered a fortnight or three weeks sooner than I wished. The fruit is swelling well, and, I believe, will receive sufficient light through the winter to enable it to ripen in much perfection. The excellence of a few Pine Apples, which ripened in this house in the last winter, leads me almost to doubt, whether the fruit in it will not ripen better, early in the spring, than in the middle of the summer, for I have observed that this species of plant, though extremely patient of high temperature, is not, by any means, so patient of the action of very continued bright light, as many other plants: and much less so than the Fig and Orange tree: possibly, having been formed by nature for inter-tropical climates, its powers of life may become fatigued, and exhausted by the length of a bright English summer’s day in high temperature. Being a plant of low stature, nature has also probably given it the power to ripen its fruit and seed, in the shade of other plants, in its native climate; and I discovered in the last summer, that it possesses the power to ripen its fruit perfectly in a lower temperature than I previously thought it capable of growing in.

“In the month of June, I gave a couple of Pine plants, which had shown fruit at six months old, and were of small size, and no value, to a child of one of my friends, to be placed in a conservatory, in which no fires were kept during the summer. In July, a storm of hail destroyed nearly, or fully, half the glass of the conservatory; and its temperature, through the summer and autumn, had been so low, that the Chasselas grapes in it were not ripe in the second week in September. In the second week of the present month (October) one of the Pine Apples became ripe, having previously swollen to a most extraordinary size, comparatively with the size of the plant; and upon measuring accurately the comparative width of the fruit, and of the stem, I found the width of the fruit to exceed that of the stem in the proportion of seven and three-quarters to one. The fruit had, of course, been propped during all the latter part of the summer, the stem being wholly incapable of supporting it. The taste and flavour of this fruit were excellent, and the appearance of the other, which is not yet ripe, and is of a larger size, is still more promising. I purpose to profit by this result in the next summer; and I hope to be able to communicate some further information to the Society in the autumn. I feel perfectly confident, that if the roots of these plants had grown in a hot-bed of any kind, their sap would have been impelled into other channels; and that their fruit would not have attained, in any degree, the state of perfection which I have described.”

This is the latest printed account of Mr. Knight’s experiments on the Pine Apple. It would be premature to draw any general conclusions in so early a stage of their progress, and might excite prejudice to anticipate the final result. That the Pine plant will grow and thrive without what is technically called bottom heat, is an obvious truth, since no plant in a state of nature is found growing in soil warmer than that of the superincumbent atmosphere. But to imitate nature, is not always the best mode of culture; for the more correct the imitation, the less valuable would be the greater part of her products, at least as far as horticulture is concerned. What would our celery, cabbage, and apples be, if their culture were copied from nature? Though the Pine Apple will grow well without bottom heat, it may grow with bottom heat still better; and though the heat of the earth, in its native country, may never exceed that of the surrounding atmosphere, it does not follow that earth heated to a greater degree may not be of service to it, in a state of artificial culture. But admitting, for the sake of argument, that the Pine plant could be grown equally well with, as without bottom heat; still it appears to us that the mass of material which furnishes this heat, will always be a most desirable thing to have in a Pine stove, as being a perpetual fund of heat for supplying the atmosphere of the house, in case of accident to the flues or steam apparatus. Besides it appears from nature, as well as from observing what takes place in culture, that the want of a steady temperature and degree of moisture at the roots of plants is more immediately and powerfully injurious to them than atmospheric changes. Earth, especially if rendered porous and spungelike by culture, receives and gives out air and heat slowly; and while the temperature of the air of a country, or a hot-house, may vary twenty or thirty degrees in the course of twenty-four hours, the soil at the depth of two inches would hardly be found to have varied one degree. With respect to moisture, every cultivator knows, that in a properly constituted and regularly pulverized soil, whatever quantity of rain may fall on the surface, the soil is never saturated with water, nor, in times of great drought, burnt up with heat. The porous texture of the soil and sub-soil being at once favourable for the escape of superfluous water, and adverse to its evaporation, by never becoming so much heated on the surface, or conducting the heat so far downwards as a close compact soil.