EVERGREENS. Those plants which imperceptibly shed their leaves and acquire new foliage, without noticeable change in their aspect, and those which, like certain biennials and alpines, maintain their leaves throughout the winter season so that they may make a quick start in the spring, are called evergreens. In the northern countries cultivated evergreens are roughly divided into two groups popularly called conifers and “broad-leaved” evergreens, the latter including laurels, rhododendrons, hollies, box, etc. The tropical flora is chiefly evergreen, and some trees, like the Magnolia glauca, that shed their foliage in the north, retain it in the south.
This evergreen character, especially where the plants are subjected to extremes of drought and wetness, or of heat and cold, has given many devices for regulating transpiration or the deleterious effects of too much moisture, such as the rolling of leaves, waxy deposits on the leaves, and various curious arrangements of pits, hairs and cells. Wherever the foliage is persistent for several years, as is the case of the holly and of many tropical trees and epiphytes, it is often thick and leathery, being provided with a thickened cuticle, especially where the leaf undergoes drought periodically. Other evergreens like cacti and rock-plants become fleshy or succulent, when living in arid conditions, storing water in their tissues and sometimes retaining it there with mucilaginous juices and salts. Furthermore they are apt to assume a more or less cylindrical shape in both leaf and stem, the foliage often being reduced to mere needles and scales, or being absent entirely. This rodlike, nearly leafless, condition is particularly noticeable in the so-called whip-plants of arid regions, which are reduced to switch branches with scales for leaves, thus greatly reducing the evaporating surface during the heated term. They often occur on the Mediterranean shores where another type of device for controlling exhalation is conspicuous; for there the evergreens are really gray, like the lavender, hoary with their envelopes of hair, just as some alpine plants, notably the edelweiss, are smothered in felted hairs. In the shadowless forests of Australia many trees reduce their evaporating surfaces by presenting only the edges of their leaves to the midday sun.
Coniferous evergreens furnish some of our most valuable forest products in the way of timber, naval stores and tanning materials, and also various food products as nuts and bark, chiefly of value to the aborigine. One or two, as the West Indian yacca and the yew, furnish cabinet woods, but the latter seems to have been used wherever it grows, chiefly for bows. Most of them also are useful for windbreaks, hedges or for ornamental planting, where shelter, concealment or winter-color is desired; various species being adapted for differing soils and climates. Some of them, as the arbor-vitae and yew, stand shearing well, and can be pruned into sundry geometrical forms; holly and box share this distinction, and the custom was formerly carried into grotesque excess in topiary gardening.
Laurel, rhododendrons and other “broad-leaved” evergreens are often valuable in shrubberies not only on account of their winter verdure but because they also have handsome blossoms or fruit; they moreover afford shelter for birds.
Their long life and perpetual verdure have caused many of the evergreen tribe, particularly the fir and mistletoe, to be included among sacred plants; and they have become adopted as symbols of immortality, of resurrection and of perennial remembrance, at funeral services and in graveyards. Several kinds, as the yew, served as “palms” on Palm Sunday. On the other hand, yews and cypresses, especially the latter, serve as emblems of eternal death and are frequently referred to in this connection in classical literature “with every, baleful green denoting death.”
Evergreens are favorite plants for decorating during the Christmas holidays; in England a certain order was observed in their disposal, as we find in Herrick's ‘Ceremonies for Candlemas Eve’:
Down with ths rosemary and bays,
Presumably these holiday garlands and decorations of evergreens — rosemary, ivy, laurel, box, holly and mistletoe — were survivals, with the Christmas tree, of pagan ceremonies and tree-worship, more or less incorporated in the rites of the early Christian churches; the mistletoe, however, was so intimately connected with Druidical rites that it was excluded from the Church decorations. There is a large trade in these Christmas greens, both of the foreign and native kinds, the latter including southern smilax, long-eared pine, ground-pine and hemlock.