[Alnus.[A] Nat. Ord.—AmentiferÆ; Linn.—Monoec. Tetra.]

The Common Alder (A. glutinosa), is the most aquatic of European trees. It grows to the height of fifty or sixty feet, in favourable situations by the sides of streams, and is a somewhat picturesque tree in its ramification as well as its foliage. It is nearly related, in nature rather than in form, to the willow tribe; it is more picturesque than the latter, and perhaps the most so of any of the aquatic species, except the weeping willow. Gilpin says, that if we would see the Alder in perfection, we must follow the banks of the Mole, in Surrey, through the sweet vales of Dorking and Mickleham, into the groves of Esher. The Mole, indeed, is far from being a beautiful river; it is a silent and sluggish stream: but what beauty it has it owes greatly to the Alder, which everywhere fringes its meadows, and in many places forms very pleasing scenes; especially in the vale between Box Hill and the high grounds of Norbury Park. Spenser probably once reposed under the shade of these trees, as he mentions them in his "Colin Clout's come home again."

One day, quoth he, I sate, as was my trade,
Under the foot of Mole, that mountain hore,
Keeping my sheep among the cooly shade
Of the green Alders on the Mulla shore.

Some of the largest Alders in England grow in the Bishop of Durham's park, at Bishop Auckland. In speaking of these, Gilpin remarks, that "the generality of trees acquire picturesque beauty by age; but it is not often that they are suffered to attain this picturesque period. Some use is commonly found for them long before that time. The oak falls for the greater purposes of man, and the Alder is ready to supply a variety of his smaller wants. An old tree, therefore, of any kind is a curiosity; and even an Alder, such as those at Bishop Auckland, when dignified by age, makes a respectable figure."

The Alder grows naturally in Europe from Lapland to Gibraltar, in Asia from the White Sea to Mount Caucasus, and in the north of Africa, as well as being indigenous in England. The flowers bloom in March and April; they have no gay tints or beauty to recommend them, and consequently afford pleasure only to the botanist or the curious observer of nature. The leaves begin to open about the 7th of April, and when fully expanded are of a deep dull green. The bark being smooth and of a purplish hue, the tree has an agreeable effect among others in all kinds of plantations of the watery tribe.

The Alder must have grown to a great size in days of yore; for Virgil speaks of vessels made of this material:

When hollow Alders first the waters tried.

And again:

And down the rapid Po light Alders glide.

Ovid also tells us that

Trees rudely hollowed did the waves sustain,
Ere ships in triumph ploughed the watery main.

Abroad this tree is raised from seed, which is decidedly the best mode, and secures the finest specimens; though in this country they are generally propagated by layers or truncheons. The best time for planting the latter, is in February or March; the truncheons being sharpened at the end, the ground should be loosened by thrusting an iron crow into it, to prevent the bark from being torn off; and they should be planted at the least two feet deep. When cultivated by layers, the planting should take place in October, and they will then be ready to transplant in twelve months' time.

The Alder is usually planted as coppice-wood, to be cut down every five or six years, for conversion into charcoal, which is preferred in making gunpowder. The bark on the young wood is powerfully astringent, and is employed by tanners; and the young shoots are used for dyeing red, brown, and yellow; and in combination with copperas, to dye black. It is greatly cultivated in Flanders and Holland for piles, for which purpose it is invaluable, as when constantly under water, or in moist and boggy situations, it becomes hardened, black as ebony, and will last for ages. On this account it is also very serviceable in strengthening the embankments of rivers or canals; and while the roots and trunks are preventing the encroachment of the stream, they throw out branches which may be cut for poles every fifth or sixth year, especially if pruned of superfluous shoots in the spring.

As Alders in the spring, their boles extend,
And heave so fiercely that the bark they rend.
Virgil, ecl. x.

Vitruvius informs us, that the morasses about Ravenna were piled with this timber to build upon; and Evelyn says that it was used in the foundations of Ponte Rialto, over the Grand Canal at Venice. The wood is also valuable for various domestic purposes.

Besides the common Alder there are introduced at least six other species:—

1. A. Glutinosa, already described.

2. Emarginata, leaves nearly round, wedge-shaped, and edged with green.

3. Laciniata, leaves oblong and pinnatifid, with the lobes acute.

4. Quercifolia, leaves sinuated, with the lobes obtuse.

5. Oxyacanthoefolia, leaves sinuated and lobed; smaller than those of the preceding variety, and somewhat resembling the common hawthorn.

6. Macrocarpa, leaves and fruit larger than those of the species.

7. Foliis variegatis, leaves variegated.