This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
The scarcity of evergreen shrubbery in our pleasure grounds is a standard theme with writers on rural taste, and comparisons with other countries in this respect invariably result unfavorably to us. That there are good reasons for such a conclusion will not be questioned by those best acquainted with our rural improvements; but they console themselves with the reflection that at no distant period we will be in a position to invite comparison instead of shrinking from it, and avoiding, as at present, all allusion to our examples of artificial landscape scenery.
We become more sensitive on the institution of these comparisons when we reflect that no country in the temperate zone is more bountifully supplied with the 'material necessary for the composition of landscape. Those who have any doubts on this point have never attempted to penetrate a Jersey swamp, or followed the course of a river in Pennsylvania. The Holly, Kalmia, and Magnolia, of the former, and the Hemlock Spruce, Rhododendron, and Yew, of the latter, are familiar examples of our native evergreens, and their beauty as ornamental plants are not surpassed by any foreign productions available for these purposes; while our deciduous trees, for variety and beauty, are beyond comparison superior to any other.
The attempts to successfully remove these native plants into cultivated grounds have so often proved abortive as to lead to the belief that the operation is generally impracticable ; but when we consider the most favorable conditions in their native localities, and compare them with the treatment the plants receive after removal, we will find sufficient reasons for the failures. Alluding more particularly to our native broad-leaved evergreen shrubs, we find them most abundant under the shade of the Hemlock Spruce, White Pine, and other evergreen trees. Thus sheltered from the aridity of summer, and shaded from the morning suns of winter, they attain their greatest beauty and luxuriance; and although frequently met with in exposed situations, they are never so healthy as when sheltered by taller evergreens, or located on the sides or at the base of slopes, where they are protected from sudden changes in winter and have the advantage of a more humid atmosphere in summer. If we therefore find these conditions most congenial to our native broad-leaved shrubs, with how much more force do they apply to those of foreign origin, accustomed to a more uniform climate - less heat and more humidity.
We see the necessity for a modification of climate, by sheltering from the excessive aridity of the atmosphere during summer and otherwise protecting from the sudden changes and extreme cold of winter.
Now let us look at the preparations made for shrubbery in our pleasure grounds. These are for the most part destitute of vegetation capable of affording either shade or shelter. It is a prevalent custom in selecting a location for a country residence, for gentlemen to "turn their backs upon the numberless fine sites with which our country abounds, and choose the barest and baldest situation in order that they may dig, level, and grade, and spend half their fortunes in doing what nature has, not a mile distant, offered to them ready made, and a thousand times more beautifully done." These "bald and bare" situations have to be planted. Catalogues are ransacked for choice and rare evergreens, or, perhaps the nearest forest is searched for a supply. In either case the results are the same - the plants linger out a miserable existence. Some few may ultimately recover the change, but their appearance is anything but ornamental, and the culture of evergreens is forthwith pronounced a failure.
In planting evergreens, therefore, more particularly those of foreign origin, we must place them in situations similar to their native localities, or otherwise modify extremes in the elements of growth so far as they are under our control. In adapting circumstances to the growth of plants, there are certain influences which can be modified, and favorable conditions which we can supply. The most favorable conditions are those which involve the least change, and that change the most gradual. It is well known that the early exposure to sun after a severe night's frost, will prove fatal to plants which would remain uninjured under a gradual thaw; consequently we find plants subjected to a northern exposure surviving through severe winters, while those seemingly more favored with a southern aspect will perish. The former never being so greatly excited, is therefore not subjected to so sudden changes, and hence its endurance.
The hardiness of plants, or the amount of cold they are capable of enduring, is, to a certain extent, dependent upon the nature of the soil in which they are growing, so far at least as concerns its contained moisture. Soil naturally wet produces late growths of succulent, unripened shoots. Early winter frosts acting upon these soft shoots expands the watery matter in their structure and disrupts their tissue. DE Candolle, in his laws of temperature with respect to its influence on vegetation, remarks that plants resist extremes of temperature in the inverse ratio of the quantity of water they contain. We know the Oak to be a hardy tree; but if we were to transfer a growing plant from a hot-house to the open air in mid-winter, it would be very likely to perish. The young, immature shoots of our hardiest plants are frequently destroyed by late spring frosts, and young plants are destroyed by cold which has no effect upon older ones of the same species. Hence the necessity of draining soil and allowing the escape of superfluous moisture. A few dollars expended in laying a permanent drain is often the only difference between failure and success in the cultivation of plants.
We have it, therefore, in our power to modify the severity of climate in winter by choosing a proper aspect and location, shading from sun, and draining of the soil But winter is not the only trying season for plants. The severity of our hot summers is more frequently injurious than we are in the habit of supposing. It is questionable whether the excessive aridity of our summers is not more hurtful to exotic evergreens than the winter's cold. Their expansive foliage presents a large surface for evaporation, and in conjunction with a diminished supply of nourishment through the roots, the plant is drained of its juices and ceases to grow. To render the extreme aridity less injurious, we must have recourse to shelter. Experiments have shown that the effect of wind is to increase the dryness of the air. "Evaporation increases in a prodigiously rapid ratio with the velocity of the wind, and anything which retards the motion of the latter is very efficacious in diminishing the amount of the former. The same surface which, in a calm state of the air, would exhale 100 parts of moisture, would yield 125 in a moderate breeze, and 150 in a high wind." We can form but a feint conception of the amount of moisture carried off by our scorching summer breezes, although its continued effect upon vegetation is well known, and its results but too apparent in stunted and arrested growth during summer.