Part 11
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.
These properties of the soil relatively to plants can never be completely attained by growing plants in pots, and least of all by growing them in pots surrounded by air. In this state, whatever may be the care of the gardener, a continual succession of changes of temperature will take place in the outside of the pot, and the compact material of which it is composed being a much more rapid conductor of heat than porous earth, it will soon be communicated to the web of roots within.
With respect to water, a plant in a pot surrounded by air is equally liable to injury. If the soil be properly constituted, and the pot properly drained, the water passes through the mass as soon as poured on it, and the soil at that moment may be said to be left in a state favourable for vegetation. But as the evaporation from the surface and sides of the pot, and the transpiration of the plant goes on, it becomes gradually less and less so, and if not soon re-supplied, would become dry and shrivelled, and either die from that cause, or be materially injured by the sudden and copious application of water.
Thus, the roots of a plant in a pot surrounded by air, are liable to be alternately chilled and scorched by cold or heat, and deluged or dried up by superabundance or deficiency of water, and nothing but the perpetual care and attention of the gardener to lessen the tendencies to these extremes could at all preserve the plant from destruction.
To lessen the attention of the gardener, therefore, to render the plant less dependent on his services, and, above all, to put a plant in a pot as far as possible on a footing with a plant in the unconfined soil, plunging the pot in a mass of earth, sand, dung, tan, or any such material, appears to us a most judicious part of culture, and one that never can be relinquished in fruit-bearing plants with impunity. Even if no heat were to be afforded by the mass in which the pots were plunged, still the preservation of a steady temperature which would always equal the average temperature of the air of the house, and the retention, by the same means, of a steady degree of moisture, would, in our opinion, be a sufficient argument for plunging pots of vigorous growing, many-leaved, or fruit-bearing plants.
Such are the observations that we think may be made relatively to Mr. Knight’s plan, without prejudice to whatever new lights he may throw out on the subject. Had it been brought forward by a less eminent horticulturist, it would not have claimed so much attention, as the plan of growing Pines without bottom-heat is generally considered to have been tried first by M. Le Cour, and subsequently by various others, and abandoned. In Mr. Knight’s hands, however, whether it fail or succeed, it is certain of doing good, by the observations it will elicit from the fertile and ingenious mind of so candid and philosophical a horticulturist.
Sir William Edward Rous Boughton has erected a house or pit at Downton Hall, similar to that of Mr. Knight, but rather wider.[2] Pines are grown in it on Mr. Knight’s plan, but the plants were not in a thriving state in November last. Charles Holford, Esq. of Hampstead, is also a disciple of Mr. Knight as to the culture of this fruit, but he has not yet been very successful.
[2] The roofs, both of this house and that of Mr. Knight, were furnished by Messrs. W. & D. Bailey, of Holborn, London.
SECT. II.
_Of other Improvements in the Culture of the Pine Apple, by different persons._
We shall first notice the improvements which respect bottom-heat, and begin with noticing an attempt made by Mr. Thomas Jenkins, of the Portman Nursery, London, to warm both the pots in which the plants are grown, and the air of the house, by the heat generated by fermenting stable-dung placed in a vault beneath.
It is only within the last three years that Mr. Jenkins has begun to grow the Pine Apple to any extent; he brings forward the plants in hot-beds and deep frames, inclosing beds of tan, and heated by linings of dung. As an economical part of the construction, we may mention that he substitutes wattled hurdles for the lower part of the frame, in contact with the tan, by which means a saving in the first cost is effected, and the heat of the dung penetrates much more readily to the tan.
Most of the plants are fruited in these pits, but some are fruited in a house, (_fig. 21._) which “though furnished with flues, yet these have been very little used. The heat imparted to the plants is produced by the fermentation of stable-dung in a pit below the plants, the top of which is covered by tiles supported by iron rafters, with the joints closely cemented, to prevent the passage of steam into the house. The pots are neither bedded in tan, nor in mould, but stand on the tiles, and the interstices between them warm the air of the house.”
The dung is managed as in West’s pit (_fig. 22._), but with the addition of being watered after it is thrown in, which is found to promote fermentation, and the intensity of the heat.
One of the earliest instances of steam being used as a bottom-heat with which we are acquainted, was that by Mr. Butler, gardener to the Earl of Derby, at Knowlesly, near Liverpool, in or about 1792. It had been used twenty years before, but chiefly for other purposes. Speechly, in 1796, knew only two instances in which steam was applied as bottom-heat; and, with M’Phail, does not think it will finally answer as a substitute for tan. Instances in which it is adopted, are now much more numerous; but time sufficient has not elapsed, and the opinions of gardeners are yet too unsettled on its merits to enable us to recommend it for adoption in general practice. For heating the atmosphere of hot-houses, there seems little (or at least much less) doubt of its being preferable to fire-heat.
Count Zubow, at St. Petersburg, employed steam to heat a pit or cistern of water, over which, at about three inches distance, a frame, covered with faggots, was placed, and on this was laid the earth, in which his Pines and other exotics were planted without being in pots. The plan is said to have succeeded, and a wholesome temperature to have been obtained and communicated to the mould above the faggots.
Mr. Gunter, as before observed, (Chap. IV. sect. 13.) had already tried the use of steam as a bottom heat without success.
Mr. John Hay, horticultural architect, tried the use of steam so early as 1794, when gardener at Preston Hall, near Edinburgh, and he gives the following account of his apparatus and success in the Memoirs of the Caledonian Horticultural Society. “The application of steam to forcing-houses early caught my attention. The first that I designed and executed in Scotland on this plan, were at Preston Hall in Mid-Lothian, in the year 1794. The fruiting Pine-stove, which is in the general suite of houses, with two peach-houses on the west, were originally adapted to steam. I entertained the hope, that steam thrown into a chamber, in the bottom of the plant pit, would act as a proper substitute for bottom heat in place of tan, as none of that substance was to be found nearer than four miles distant, and when wanted was often difficult to be procured. Other more general considerations also made me desirous of procuring some substitute, particularly the necessity of repeatedly shifting the plants to renew the heat, when the bark in the plant-pit gets cold: these shiftings, besides the trouble, often retard the growth of the plants. Again, if the heat of the fermentation of the tan rise much above ninety-six degrees, (which it often does), and if the pots be fully plunged in the tan at such a time, many instances have been known of the roots of the plants being burned, and some of them being destroyed altogether. This, indeed, may be considered as one of the principal reasons why so many are unsuccessful in the culture of this fine fruit. With the view of obviating the above difficulties, the bottom of the fruiting Pine-pit was constructed with a chamber below, into which steam was introduced by means of copper and lead pipes from a boiler placed in the shades behind: the top of the chamber was constructed of rafters, on which were placed broad grey slates, laid on loose, without filling up the vacancies between them. The not making them close, I afterwards found to be an error; for the moisture, from the condensation of the steam, penetrating through the openings at the joining of the slates, communicated too much wetness to the bottom of the pots; but I found, that there was a sufficient quantity of heat to be obtained from the steam for heating the plant-pit, provided the bottom were close. I therefore discontinued this plan; and I had not an opportunity of making any farther experiment on the subject in this place. From the same boiler, I conducted into the two peach-houses adjoining, a range of pipes furnished with steam-cocks. They passed the whole length of the houses, (101 f. 6 in.). By means of these, the peach-houses were regularly steamed near one hour a-day in the evening, in the time of flowering and of fruit-setting. Steaming, it may be remarked, is very important at these times. In after periods, when I had not an apparatus for the purpose, I always steamed the peach-house with a large piece of cast-iron, made red hot in one of the furnaces, and put into a white-iron pail nearly full of water; the whole water thus evaporating into steam. I was always successful, while in practice as a gardener, in raising a full crop of peaches; and think that much was owing to attention to steaming.
“I afterwards erected Pine-stoves for John Hervey, Esq. of Castlesemple, to be heated by steam; and one of the plant-pits had a chamber below, with a close bottom, into which chamber, steam was thrown by means of cast-iron pipes. About the same time, I was applied to by Sir Hew Hamilton Dalrymple, Bart. (through Mr. James Dodds, his gardener), to examine his Pine-stoves at Bargany, and to report whether I thought they could be improved, as he hitherto had not been so successful in Pine-Apples as he expected. One principal cause was, the difficulty of obtaining tan. Upon my report, it was to be determined, whether to give up the Pine-Apple culture altogether, or endeavour to improve the stoves.
“Upon examining, I advised the heating of the atmosphere of the houses with steam; and in place of using tan, the heating of the bottom of the plant-pit with steam also.” This advice was adopted, and eighteen months after the plan was executed, the gardener, Mr. James Dodds, gives the follow-account of his success.
“It is now eighteen months since I first began to heat the Pine-stoves here with steam. I have thus been enabled to give it a fair trial, and I am fully satisfied that it is superior to the old method of heating by fire-flues. I have found the plants to grow more luxuriantly, and perfectly clean of any kind of _insects_. The moist heat arising from steam is well known to be hostile to all kinds of vermin. It is, besides, more economical: our Pine-stoves here are seventy feet long, it formerly took two fires to keep up the heat of the atmospheric air of the house, whereas in the new method of heating by steam, one fire to heat the boiler is sufficient, except in very cold nights, when I have found it necessary to light a very small fire to the flue, to meet the decline of the steam in the morning, and this only to the fruiting-house in the spring months, when the Pines begin to show their fruit. In short, I have found no difficulty in keeping up the heat of the house to sixty degrees, by making up the fire to the boiler at ten o’clock at night, and at six o’clock in the morning.
“With regard to the bottom heat for the Pine-plants, by steam from the same boiler, I find, by allowing the steam to remain in the chamber below the plants about two hours a day, the pit is kept constantly at the temperature of from ninety to ninety-five degrees, which I have found to be as high as the roots of the plants are able to bear. I would, therefore, say ninety degrees to be the standard height, which I have myself adopted, allowing it to fluctuate down. If our succession Pine-pit had been altered to have been heated by steam, as the fruiting one is, which the boiler is perfectly able to do, the saving in tan alone would more than pay the interest of all the money laid out on erecting the whole steam apparatus.
“The above is my candid opinion on the subject, as far as my practice has enabled me to speak. I am, &c.
“JAMES DODDS.”
* * * * *
The best stoves for combining the culture of the Pine and Vine in Scotland, have been constructed by Mr. Hay, of which fine examples occur at Lord Duncan’s, Lundie-house, near Dundee, and the Earl of Roseberry’s, at Dulmeny-park (_fig. 23._), near Edinburgh.
As substitutes for tan, leaves are the common resource, but any vegetable matter of slow putrefaction may be employed, as chopped spray of hedges or copse, wood-shavings, saw-dust, &c. and in Scotland, it has been found that flax-dressers’ refuse keeps up a moderate heat for a longer period than any other material.
The mode of employing the vigour remaining in the old stock or plant after the fruit is cut, to nourish, for a certain time, the sucker or suckers which may be growing on it, was practised by Speechly; but scarcely to the extent which it has been carried lately. This, we think, a considerable improvement, if kept within certain limits; but, if carried too far, what might be gained by the sucker coming earlier into fruit, would be lost by the retardation of the plant’s own suckers.
On Nov. 3. 1818. “A Queen Pine, grown by Peter Marsland, Esq. of Woodbank, near Stockport, was exhibited to the Horticultural Society. It weighed three pounds fourteen ounces, measured seventeen inches in circumference, and was peculiarly well-flavoured. The singularity of this Pine was its being the produce of a sucker which had been removed from the parent-root only six months previous to the time the fruit was cut. The plant on which the sucker grew had produced a fruit, which was cut in October, 1817; the old stem, with the sucker attached, was allowed to remain in the Pine-pit till May, 1818; at that time the sucker was broken off, potted, and plunged into a fresh pit; it soon after showed fruit, which, in the course of four months, attained to the weight and size above stated. Mr. Marsland is in the practice of producing Pines in this way with equal success and expedition. His houses are all heated by steam.” _Hort. Trans._ iv. 52.
On the 17th of Oct. 1819, specimens of the New Providence, globe, black Antigua, and Enville, were exhibited, all which were produced in a similar manner to the above. P. Marsland considers, that “though not of the largest description, yet as far as beauty of form and richness of flavour are concerned, they would not yield to fruit of more protracted growth.” The success which has attended this gentleman’s mode of “treating the Pine, so as to insure the production of fruit within twelve months from the cutting of their previous produce, has been perfectly satisfactory;” and the following is his account of it. “In November, 1819, as soon as the fruit had been cut from the Pine plants, which were then two years old, all the leaves were stripped off the old stocks, nothing being left but a single sucker on each, and that the strongest on the plant; they were then placed in a house where the heat was about sixty degrees, and they remained till March, 1820. At this period the suckers were broken off from the old stocks, and planted in pots from eight to twelve inches in diameter, varying according to the size of the sucker. It may be proper, however, to observe, that the length of time which the young sucker is allowed to remain attached to the mother plant, depends in some degree upon the kind of Pine; the tardy fruiters, such as the black Antigua, and others, require to be left longer than the Queen, and those which fruit readily.
“After the suckers had been planted, they were removed from the house, where they had remained while on the old stock, to one in which the temperature was raised to seventy-five degrees. Immediately upon their striking root, the largest of the suckers showed fruit, which swelled well, and ripened between August and November, being, on the average, ten months from the time the fruit was cut from the old plant, and seven months from the time the sucker was planted. The fruit so produced, though, as may be expected, not of the largest description, I have invariably found to be richer and higher flavoured than that grown on older plants. The suckers of inferior strength will not show fruit in the same season, but in the following they will yield good fruit, and strong suckers for a succeeding year’s supply. Those suckers are to be preferred which are produced on plants that have ripened their fruit in November, for those taken from plants whose fruit is cut in August, or earlier, are apt to show fruit in January or February, while yet remaining on the mother-plant. But whenever this happens, the sucker should be broken off immediately upon being perceived, and planted in a pot so as to form a root of its own, to maintain its fruit.” _Hort. Trans._ iv. 392.
This experiment shows what can be done; though it must be obvious that a considerable part of the saving in time is lost by the small size of the fruit. Mr. Baldwin, in our opinion, has hit on the proper use of this mode, the principle of which, as already observed, consists in the employment of the otherwise lost vigour of the old stock. He contrives to produce tolerably sized fruit, and to have such a degree of vigour in his suckers, as that they are able, in their turn, to throw out other vigorous suckers to succeed them. In aid of this, he often earths up the old stock, so as to cover the lower end of the sucker; and partially wrenching it off, he, by these means, obtains for it a good stock of roots before he renders it an independent plant.
Where heat is to be supplied from fermenting horse-dung, we should recommend for trial a pit invented by J. West, of Castle Ashby, in Northamptonshire. (_fig. 22._) Nine years’ experience enable its inventor to recommend it for neatness of appearance, the power of regulating the heat to the greatest nicety, and for forcing asparagus, strawberries, and the most delicate kinds of cucumbers. By raising the walls of the pit higher above the earth, it is evident it would answer equally well for growing Pines, or forcing shrubs or tall growing plants.
The dung is placed in a chamber (E) three feet and a half deep, being about eighteen inches below the surface-line; the walls (G) which surround it are nine-inch brick-work; both on the front and at the back of the chamber are two openings (A), about two feet six inches square each, with moveable doors, through which the dung is introduced; the doors fit at bottom into grooves (B), and are fastened by a wooden pin and staple at top. In front of the doors, is a small area (C) sunk in the ground, surrounded by a curb of wood, by which the introduction or removal of the dung is facilitated. Along the centre of the chamber is a bar (D), which serves as a guide for packing the dung; and across the top, at intervals of twelve inches, are placed, on their edges, cast-iron bars (H), two inches wide, and three quarters of an inch thick, to support a layer of small wood, bushes and leaves (I), over which is laid the soil for the plants (K). Just below the level of the bars all round the dung-chamber, are holes (F), passing in a sloping direction through part of the wall into a cavity (G) in the upper part of the wall at the back front and both ends of the pit. In the exterior part of the back wall, are holes with plugs (L), to let out the steam and heat at discretion.
At the commencement of forcing, half the chamber is filled longitudinally with dung, and if the doors are kept shut, this will afford sufficient heat from twelve to eighteen days. As the heat declines the other half of the chamber is filled, and the temperature is kept up by additions to the top of the dung, on either or both sides, as it settles. When the united heat of the two sides ceases to be sufficient, the side first filled must be cleared out, and mixed with fresh dung and replaced, and so on, adding and turning as circumstances require. _Hort. Trans._ iv. 220.
As an improvement on the construction of this pit, we would suggest the perforation of the whole of the side walls (_fig. 24. a_), in order to admit the steam more readily than it can find admittance by the single range of openings adopted by Mr. West. Where pits on Mr. West’s plan are already built, a substitute for this perforation in the side walls may be found in the application of a wattled hurdle against them (_fig. 24. b_), as has been adopted by Mr. J. B. Mackay, in the Comte de Vande’s garden at Bayswater.