What follows is a chapter from Nathaniel Bagshaw Ward’s 1852 treatise on terrarium gardening.

ON THE NATURAL CONDITIONS OF PLANTS.

To enter into any lengthened detail on the all-important subject of the Natural Conditions of Plants would occupy far too much space; yet to pass it by without special notice, in any work treating of their cultivation, would be impossible. Without a knowledge of the laws which regulate their growth, all out attempts must be empirical and more or less abortive. When we survey the vegetation on the surface of the earth, we are struck with the endless diversities of form which present themselves to our astonished gaze, from the magnificent palms of the Tropics and the bread-fruit of the Polynesian Islands to the reindeer moss of Lapland, or the red snow of the Arctic regions. Yet the growth of all is governed by immutable laws, and they owe their forms to varying climatal conditions.

In Rome upon Palm Sunday
They bear true palms,
The Cardinals bow reverently
And sing old Psalms :
Elsewhere their Psalms are sung
‘Mid olive branches.
The holly bough supplies their place
Among the avalanches :
More northern climes must be content
With the sad willow.—GOETHE.

HEAT.

The heat to which plants are subjected varies from 30° or 40°below zero to 170° or 180° Fahr. In Spitzbergen, the earth in the middle of the short summer is never thawed to more than the depth of a few inches, and the stem of the only tree, a little willow, if tree it can be called, runs under ground for several feet within an inch or two of the never-melting ice, whilst in Mexico the heat rises to 170° or 180°, and the ground is occupied by cactuses, whose structure is such as to enable them to resist the extremest degree of drought. Were it not for such plants, these hot regions would form impassable barriers between neighbouring countries. No water is to be found in these districts, nor anything to eat save the fruit of the Petaya, which Hardy tells us was the sole subsistence of himself and his party for four days. This, unlike other luscious fruit, rather allays than creates thirst, while, at the same time it satisfies, to a certain degree, the sensation of hunger. St. Pierre calls the cactuses, the “Springs of the Desert.” The wild ass of the Llanos, too, knows well how to avail himself of these plants. In the dry season, when all animal life flies from the glowing Pampas, when cayman and boa sink into death-like sleep in the dried-up mud; the wild ass alone, traversing the steppes, knows how to quench his thirst, cautiously stripping off the dangerous spines of the melocactus with his hoof, and then, in safety, sucking the cooling vegetable juice. The Providence of God is equally manifested in cold countries, as in Lapland─where the rein-deer moss furnishes the sole food, during winter, of the rein-deer, without which the inhabitants could not exist.

LIGHT.

” Even as the soil which April’s gentle showers
Have filled with sweetness, and enriched with flowers,
Rears up her suckling plants, still shooting forth
The tender blossoms of her timely birth ;
But if denied the beams of cheerly May,
They hang their withered heads and fade away.”

It is hardly possible to overrate the influence of light upon plants. Its intensity, however, varies exceedingly. Sir J. W. Herschel says that the light at the Cape of Good Hope, when compared with that of our brightest summer’s day in England, is as 44° to 27°. In other situations, plants are found growing where the light is not more than half of what would be given by and ordinary candle. Very much of our success in horticulture depends upon the proper amount of light; and, the fact that flowering plants generally require more light than ferns, is one principal reason why the former do not succeed so well in closed cases in rooms, as the latter. A plant of Linaria Cymballaria lived for some years in a closed case on the top of a portion of Tintern Abbey. The branches which grew towards the light, invariably produced leaves of the full size, with perfect flowers and fruit, whilst those branches which trailed down between the model and the window, and were nearly without light, never produced either flowers or fruit, and the leaves were not more than one-tenth of the ordinary size.

This specimen was exhibited to the Chancellor of the Exchequer, * to prove to him the depressing effects of want of light ─ and want of light alone ─ as all the other conditions of the plant were the same. Some fairy roses, which had flourished in a case standing in the open air for seven or eight years, were nearly killed by being placed in a dark part of the transept of the Great Exhibition for six or seven weeks; this temporary deprivation of light doing more injury than all the variations or our climate for so long a period had been able to effect. Light also, by sustaining the vital energies of a plant enables it to resit the depressing effect of cold. The secretions of plants, too, are always developed in greater perfection according to the intensity of the light (combined with heat), and this to such a degree that the same species of plant─e.g. Cannabis sativa─which is inert in a temperate region, produces, in the tropics, secretions of a powerful and dangerous character. Man makes use of these facts in rendering many plants available for food, that could not otherwise be eaten, as the endive, celery, &c “

In North America, the operation of light in colouring the leaves of plants, is sometimes exhibited on a great scale, and in a very striking manner. Over the vast forests of that country clouds sometimes spread, and continue for many days, so as almost entirely to intercept the rays of the sun.

*Upon the occasion, in 1850, of a deputation waiting on the Chancellor for the abolition of the window duties.

In one instance, just about the period of vernation, the sun had not shone for twenty days, during which time the leaves of the trees had reached nearly their full size, but were of a pale or whitish colour. One forenoon the sun broke through in full brightness, and the colour of the leaves changed so fast, that, by the middle of the afternoon, the whole forest, for many miles in length, exhibited its usual summer’s dress.”—Ellis.

MOISTURE.

Without moisture, there can be no vegetation. Whatever may be the degree of heat, or of cold, or deficiency of light, if there be but moisture, plants of some kind are to be found. They form the oases in the sandy deserts, vegetate in the snow of the Arctic regions, and in and on the borders of thermal springs. The degrees of moisture vary exceedingly. The late Mr. Allan Cunningham often expressed to me his surprise at the extreme dryness of the atmosphere and soil in New Holland, where many species of plants grew, species, too, which did not appear to be constructed like the cactuses, to resist extreme drought ; but there, banksias and acacias would live for months without either dew or rain, in soils where not a particle of moisture was to be found on digging several feet below their roots. Numberless other plants, independently of those which live in water, cannot exist unless the atmosphere and soil are saturated with moisture— such as Trichomanes speciosum, and numerous tribes of plants which adorn the rocks in waterfalls, &c. One of the most important objects in gardening—but one which is too frequently overlooked—is to furnish plants with the requisite amount of moisture. That acute observer, Dr. Hooker, remarks that in Dr. Camp bell’s garden, at Darjiling (Sikkim Himalaya), there is a perpendicular bank, fifteen feet high, exposed to the west, and partly sheltered from the south-west by a house. Rhododendron Dalhousiæ has annually appeared on this, the seeds being imported by the winds, or birds, from the neighbouring forest ; the seedlings, however, perished till within the last two years ; since which time there has sprung up abundance of Lycopodium clavatum, and a Selaginella with Marchantia, which retain so constant a supply of moisture, that the Rhododendron now nourishes and flowers in perfection. This fact serves to explain why many plants in a state of nature (where the ground is completely covered with vegetation), succeed so much better than in the well-kept garden of the amateur ; the continued exhalation from the plants ensuring a constantly moist atmosphere, which is of as much use to vegetation as the rain.

In some countries, as on the coast of Peru, rain scarcely ever falls, but, from May, for six months, a thin veil of clouds covers the coast, from 9 a.m. to 3 p.m. From the first appearance of the cloud, the sand hills, as if by enchantment, assume the features of a beautiful garden. It is a well known fact, that many hilly countries have been rendered quite sterile, in consequence of the indiscriminate destruction of their trees, the roots of which, taking up more water from the deep-seated springs than the plants requires for their own use, distil the surplus through the leaves upon the ground, forming so many centres of fertility. ” Spare the forests, especially those which contain the sources of your streams, for your own sakes, but more especially for that of your children and grand children.”

REST.

” The meanest herb we trample in the field, Or in the garden nurture, when its leaf In autumn dies, forebodes another spring, And from short slumber wakes to life again.”

All plants require rest, and obtain it in some countries by the rigor of winter ; in others, by the scorching and arid heat of summer. Cultivators often fail in their attempts to grow certain plants from want of attention to this essential point. Thus, most Alpine plants, which enjoy an unbroken rest under the snow for several months, are very difficult of culture in our mild and varying winters. Messrs. Balfour and Babington, whilst recently exploring the lofty mountains of Harris, found the climate to be so modified by the vicinity of the great Atlantic Ocean, that, notwithstanding their northern lati- tude (68°), many of the species inhabiting the Highland districts of Scotland were wholly wanting, and the few which they saw were confined to the coldest and most exposed spots. From the same cause many plants grow there which are not known to grow in so northern a latitude in Britain.

The winter of 1850—51 was ushered in by some heavy falls of snow, with which I filled my.Alpine case, giving the plants a perfect rest of three or four months, and with a most satisfactory result—the Primula marginata, Linncea borealis, and other species, flowering much finer than usual. Many of these beautiful plants would, I am convinced, succeed well, if kept for five or six months in an ice-house.

Plants in hot countries have their periods of rest in the dry season. In Egypt the blue water-lily obtains rest in a curious way. Mr. Traille, the gardener of Ibrahim Pacha, informed me that this plant abounds in several of the canals at Alexandria, which at certain seasons become dry; and the beds of these canals, which quickly become burnt as hard as bricks by the action of the sun, are then used as carriage roads. When the water is again admitted, the plant resumes its growth with redoubled vigour.

On the sandy flats at the Cape of Good Hope the heat is so great, that Sir J. F. W„ Herschel, upon one occasion, cooked a mutton-chop on the.surface of the burnt soil ;* and this extreme heat,coupled with intensity of light, will readily account for the uncertainty which attends the growth and flowering of Cape bulbs in this country.

There are some countries in which there are two fruit-bearing seasons; where the vine, unable to obtain rest, either from the cold of winter, or the dry heat of summer, is made to bear a second crop of fruit — the ingenuity of man, overcoming obstacles apparently insurmountable. I am indebted to one, who, whilst he is dedicating his life to the holy cause in which he is engaged, does not, at the same time, disdain (to use the quaint but expressive language of Sir Thomas Browne), ” to suck divinity from the flowers of nature” — I mean the Bishop of Ceylon, for a knowledge of the fact that at Jafna, the artificial hybernation of the vine, necessary in a tropical country, is produced by laying the roots bare to the depth of two feet, for four or five days, by which time all the leaves are shed. This is done with those that- have borne fruit during the first of the two fruiting seasons. They are then pruned, covered again with manure, and constantly watered. In this way the vine is brought to bear fruit, small in size, but of good flavor. In our own country we often witness the effects produced by continuous heat in long summers. The rest thus obtained causes many plants to flower on the recurrence of autumnal rains, which would not otherwise have flowered until the ensuing spring — as the laburnum and many others.

To suit all the varied conditions to which I have thus briefly alluded, and under which plants have been found to exist, they have been formed of different structures and constitutions, to fit them for the stations they severally hold in creation, so that almost every different region of.the globe is characterized by peculiar forms of vegetation, dependent upon climatal differences ; and thus a practised botanical eye can, with certainty, in almost all cases, predict the capabilities of any previously unknown country, by an inspection of the plants which it produces. It were much to be wished that those upon whom the welfare of thousands of their starving emigrant countrymen depends, possessed a little more of this most useful knowledge.

But in order to give a clearer idea of the close connexion existing between vegetation and climate, let us take one or two examples from Nature. We shall find some plants restricted to certain situations, whilst others have a wide range, or greater powers of adaptation. It is not, perhaps, going too far to assert, that no two plants are alike in this particular, or, in other words, that the constitution of every individual plant is different ; and nothing would be more delusive than to imagine, that because two plants are found associated in a state of nature, the same treatment would be applicable to both, or that both would be equally amenable to culture. Thus the Hymenophyllum and the common London pride (Saxifraga umbrosa) are found growing together in rocks on the shores of the Lake of Killarney ; the one is so difficult of culture that the Irish have a saying, ” that he who can grow the fairy fern is born to good fortune,” whilst the Saxifrage, on the contrary, will grow in any situation, and will last for years, without the slightest attention, under the most depressing in fluences.

We have another remarkable example in the auricula, which is only found indigenous in the Alps, growing in company with plants, mostly very difficult of culture.

The Cerasus virginiana affords an interesting illustration of the effects of climate upon vegetation: in the southern states of America it is a noble tree, attaining one hundred feet in height ; in the sandy plains of the Saskatchawan it does not exceed twenty feet ; and at its northern limit, the great Slave Lake, in lat. 62°, it is reduced to a shrub of five feet. Again, in ascending a lofty mountain in tropical regions, we have exhibited to our admiring gaze the different forms of vege tation which are to be seen in all countries, from the bananas, the palms, bamboos, &c, of the plains, to the oaks, beeches, &c, of temperate climes, and the berry-bearing plants of Arctic regions up to the red snow. But we need neither travel to America, nor ascend mountains for in stances of this sort ; we have them everywhere about us. I have gathered on the chalky borders of a wood in Kent, perfect specimens, in full flower, of Erythrcea centaurium, consisting of one or two pairs of most minute leaves, with one solitary flower; these were growing on the bare chalk, fully exposed to the sun. By tracing the plant towards, and in, the wood, I found it gradually increasing in size, until its full development was attained in the open parts of the wood, where it became a glorious plant, four or five feet in elevation, and covered with hundreds of flowers. Let us pause here a moment and reflect deeply on the wonders around us. We shall find a continued succession of beauties throughout the year, beginning with the primrose, the violet, and the anemone; these giving place to the or chises, and these again to the mulleins, campanulas, and various other plants, all in their turn delighting the eye, and gladdening the heart; nor is the winter season devoid of interest; the surface of the ground, and every decaying leaf and twig, are inhabited by a world of microscopic beauties. All these have maintained their ground without interfering with each other, year after year, and generation after generation. The same page in the great Book of Nature, which filled the mind of Ray with the wisdom of God in creation, lies open to our view.” All these things live for ever for all men, and they are all obedient. All things are double one against another, and He hath made nothing imperfect. One thing establisheth the good of another, and who shall be filled with beholding His glory?” Can man, with all his boasted wisdom, realize such a scene as I have just attempted to depict? He cannot; he would feel that,” when he hath done, then he beginneth, and when he leaveth off, then he shall be doubtful.”

I have dwelt at some length on the natural conditions of plants, convinced of the paramount importance of a knowledge of these conditions to all cultivators of plants, and cannot do better than sum up in the words of a great philosopher of the present day.”

“If the laws of Nature, on the one hand, are invincible opponents, on the other, they are irresistible auxiliaries ; and it will not be amiss if we regard them in each of these characters, and consider the great importance of them to mankind:—

” Firstly. In showing us how to avoid attempting impossibilities.
” Secondly. In securing us from important mistakes in attempting what is in itself possible, by means either inadequate, or actually opposed to the ends in view.
” Thirdly. In enabling us to accomplish our ends in the easiest, shortest, most economical, and most effectual manner.
” Fourthly. In inducing us to attempt, and enabling us to accomplish objects, which, but for such knowledge, we should never have thought of undertaking.”—HERSCHEL.

* In the Regio calida-sicca of Brazil, the forests that exist have seldom that fulness and lofty growth of those on the coast, and, during the dry months, the leaves are deciduous, on which account they are called, in the language of the Brazils, light-forests (Caa-tinga). What is extraordinary, if no rain falls, they can remain for many years without producing foliage; but when at last the showers descend, in the course of forty-eight hours they are clothed in the most delicate and tender green.