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gardenei-s, as Trotter, of Alva, a veiy liigli and exposed situation on tho Ochil hills, never
cover then- hot-walls; but in ripening the wood in autumn, and in saving the blossom and
setting the fniit in spring, keep up such fires as will repel the frost, and eva])oratc the wet
that might fall on the wall. “ No danger,” Ti'ottcr obseiwcs, “ is to bo apprehended
from the severity of the spring months, even when exposed to all sorts of w eather; eveiy
kind of covering being superseded by the genial heat of the wall.” This he has long
experienced, even in England, but especially in Scotland, to be “ the best preseiwative
of the blossom of young fmits.” (Caled. Mem., vol. ii. p. 113.)
2627. Accelerating by fiued borders lias been occasionally attempted, but can never
succeed by fire h e a t; by tubes of hot water, perhaps, something might he done, but the
heat can always be more economically applied by means of pits or frames, placed on
raised beds of mould, with arches, or .some similai- contrivance, underneath. (See a
description of a flued border in Keil’s Treatise on the Peacli Tree, Svo. 1780.)
2628. Accelerating hy covering with glass cases, of different sizes and descriptions, probably
succeeded to housing. The Romans arc supposed to have hastened the ripening of
grapes and peaches, by placing them under talc cases (6 5 .); and a French author,
Berard, informs us, that the origin of forcing the vine arose from one Gordon observing
that a shoot, which had entered his room-window through a crcvice, ripened its fmit
some time before those branches of the same tree which remained in the open air. The
practice of forcing peaches in Holland is said to have originated from a gardener near
Haarlem putting hotbed lights against his walls to ripen peaches in a had season. By
a mere covering of glass, without any description of bottom heat, or any auxiliary mode
of acceleration, almost all fruits and flowers which grow in the open air in tliis country
may be forwarded from one fortnight to ono month, according to the season. Fraits
may, by the facile means thus afforded of covering and protection, be retained in a ripe
and plump state from ono to three months; so that, in general, it may be obsei-vcd, that
cold frames, as they arc called, and mere glass cases, will double the ordinary time of
enjoying hardy fm its ; and certainly they greatly increase the flavour of such as ripen
late, and especially of the peach and of the vine.
2629. Accelerating by glass cases and artificial heat combined is effected by hotbeds,
pits, and hothouses.
2630. Accelerating hy the common hotbed is an ancient, general, but still somewhat
precarious and unmanageable mode. The heat being produced by a fermenting mass of
vegetable matter, over which is placed the earth containing the plants, it becomes difficult
to regulate any excess of i t ; and the plants are sometimes, in the empirical phrase,
burnt. Wlien, however, the heat declines, it is readily renewed by linings, or a surrounding
layer of dung. To remedy the defects of the common hotbed, and prevent
the possibility of burning the plants, by intei-posing a stratum of air between the dung
and the mass of eai-th which contains them, is the object of the vaulted pit and M’Phail’s
frame (fig. 563.); to which there is no other objection, than tliat of the gi-eatcr
original cost. These structures actually save dung, and ai-o more agreeable to the eyes
of those who value order and neatness than dung-bcds.
2631. Accelerating hy means o f walled pits is very similar to that of forcing by hotbeds,
with the advantages of having more room between the suiface of the beds and the glass for
the tops of shi-ubs, and of the glass having a better slope; but with the disadvantages of a
chance of bui-ning in tho first instance, and .no power of increasing the bottom heat when
it once declines. Bark is generally used to lessen the first evil, as it does not fei-ment so
powerfully as d u n g ; and the second is remedied by a sun-ounding flue. Such pits are
much used in aU tbe branches of garden-culture. Henderson, of Brechin, proposes to
lay on the surface of beds of tan, or on hotbeds, pits, pineries, &c., fine drifted river or
sea sand, 3 in. deep. “ This covering,” he says, “ possesses many advantages.
I t will extirpate the slater or woodlouse ( Oniscus AseUus), as the nature of the sand prevents
the insect from concealing itself from the rays of the sun. In dung hotbeds, it
keeps down the steam. To fmit,. it affords a bed as warm aud as dry as tiles or slates.
This covering also retains the moistm-e in the earth longer than any other, and is itself
sooner dry. I t gives the houses a clean, neat appearance, and, though it cannot be
expected to remove the infection, where already introduced, will be found a powerful
preventive of that great evil, mildew.”
2632. Accelerating by means o f hothouses is the masterpiece of this branch of culture,
and is but of modem invention, being unknown till the end of the 17th century. Improvement
in the foi-m as well as management of these buildings has, as m every other
case, been progressive; and there is now a great choice of the forms adopted, the materials
used in the construction of these forms, and the mode of producing artificial heat.
2633. There are two leading modes o f accelerating plants in hothouses: the first is, by
placing them there permanently, as in the case of the peach, vine, &c., planted in the
g ro u n d ; and the second is, by having the plants in pots, and iiiti-oducing or withdrawing
them at pleasm*e. As far as respects trees, the largest crops, and with far less care, are
produced by the first method ; but, in respect to herbaceous plants and shrubs, whether
culiuary, as the strawberry aud the kidneybean, or oniamental, as the rose and the pink,
the latter is by far the most convenient method, and it is also the best adapted for
affording very early crops (2623.). Where large pots are used, the peach, chen-y, fig,
&c., will produce tolerable crops. Knight has obseiwed, that “ vines aud other fruit-trees,
when abundantly supplied with water and manure in a liquid state, require but a very
small quantity of m o u ld ;” and he adds, “ a pot contaimng 2 cubic feet of very rich
mould, with proper-subsequent attention, is fully adequate to nourish a vine, which, after
being praned in autumn, occupies 20 square feet of the roof of a hothouse ; and I
have constantly found that vines in such pots, being abundantly supplied with food and
water, have produced more vigorous wood, when foi-ccil very early, than others of the
same varieties, whose roots were permitted to extend beyond the limits of the house.”
(Hort. Trans., vol. ii. p. 373.)
2634. When trees are planted for a permanency within, or close to the outside of, a hothouse,
the soil requires to be prepared of depth and quality according to the nature of
the tree ; and a principal consideration is to form, if such does not naturally exist, a subsoil,
which shall be impenetrable to tbe roots. The depth of soil on such a substratum
need not in general be great, provided it be rich. Formerly a depth of 3 ft. or 4 ft. was
recommended ; but Hayward proposes to have his fruit-tree borders only 15 in. or 18 in.
deep ; which is conformable to an observation of Ilitt’s, that the finest crop of peaches
he had ever seen, grew on trees which were nourished from a border not more than 1 ft.
deep, with a compact rock below. Nicol allows from 24 in. to 30 in. of soil. Knight is of
opinion that “ a large extent and depth of soil seem to be no farther requisite to trees
than to afford them a regular supply of water, and a sufficient quantity of organisable
matter ; ” and he thinks “ the rapid gi-owtli of plants of every kind, when their roots
are confined in a pot to a small quantity of mould, till that becomes exliausted, proves
sufficiently the tm th of this position.” (Hort. Trans., vol. ii. p. 127.)
2635. 'The operations o f forcing chiefly respect the admission of air, the supply of heat,
of light, and of water. The grand effect is produced by heat, and the great art is
just to supply as much as will harmonise with the light afforded by the sun and the
nature of the species of plant to be forced. All the operations of natui-e are gi-adual ;
and a good gardener wiU always follow these as the safest examples. He will never
be anxious to apply artificial heat before buds have naturally sivoUen ; he will then
increase the temperature gradually for some weeks ; he will, in pai-ticiilar, guai-d against
any sudden decrease of warmth, it being most necessary, towards success, to continue
the course of vegetation uninterruptedly, through foliation, inflorescence, and fructification.
2636. Heat and light. A u eiTor in hothouse culture in general, of very considerable
importance, and which has prevailed till lately, consists in not adjusting the heat of art
to the light of the sun. In cloudy weather, and during night, the artificial atmosphere
is kept hot by fires, and by the exclusion ofthe external air; while in clear days, and during
sunshine, fires arc left off, or allowed to decline, the external air is admitted, and tho
atmosphere within is reduced to the temperature of that without. As heat in nature is
the result of the shining of the sua, it follows that when there is most light there is most
heat, but the practice in forcing is very generally the reverse. “A gardener, in forcing,”
Knight observes, “ generally treats his plants as he would wish to be treated himself;
and consequently, though'the aggregate temperature of his house be nearly what it ought
to be, its temperature, during the night, relatively to that of the day, is almost always too
high.” In one of Knight’s forcing-houses, in which grapes were grown, lie always wished
to see its temperature, in the middle of every bright day in summer, as high as 90° ; “ and
after the leaves of the plants have become dry, I do not object to 10° or 15° higher.
_ In the following night, the temperature sometimes falls as low as 50° ; and so far am I
from thinking such change of temperature injurious, I am well satisfied that it is generally
beneficial. Plants, it is true, thrive well, and many species of fmit acquire their
greatest state of perfection in some situations within the ti-opics, where the temperature
in the shade does not vary in the day and night more than 7° or 8° ; but in these
climates, the plant is exposed during the day to the full blaze of a tropical sun, and
early in the night it is regularly drenched with lieaiy wetting dews ; and consequently
it is very differently circumstanced in the day and in the night, though the temperature
of the air in the shade at both periods may be very nearly the same. I suspect,” he
continues, “ that a large portion of the blossoms of the cherry and other fruit trees in
the forcing-house often proves abortive, because they are forced, by too high and unifonn
a temperature, to expand before the sap of the tree is properly prepared to nourish them.
I have, therefore, been led, during the last three years, to try the effects of keeping up a
much higher temperature in the day than in the night. As cai-Iy in the spring as I
wished the blossoms of my peach trees to unfold, my house was made warm during the
middle of the day ; but towards night it was suffered to cool, and the trees were then
sprinkled, by means of a large syringe, with clcai- water, as nearly at the tempcratui-c at
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