« PreviousContinue »
but this horizontal rod may be dispensed with where the rods are planted crossing each other; as, when that is the case, each is kept in its place by a single tie at any point of intersection near the top of the fence. The advantage of placing the rods either sloping or intersecting is, that they push equally throughout; whereas, when placed perpendicularly, they push chiefly at the summit. The durability of fences of this description depends entirely on their management; on suffering no one rod, or plant, to grow more vigorously than another; and cutting the hedge regularly every year, either in summer for the leaves as fodder, or in November for the twigs for basket-making; and in keeping the base of the hedge at least twice the width of the top.
Culture of Willows as ornamental Trees or Shrubs. It is almost needless to repeat what we have before stated on the subject of rendering trees and shrubs either gardenesque, or picturesque, according to the character of the scene in which they are to be placed. As gardenesque objects, all the shrubs, as well as the trees, will have most effect when trained to a single stem, if only to the height of 2 ft. or 3 ft. This alone gives them the character of art. All the trailing sorts, such as S. herbàcea, S. reticulata, &c., to be truly gardenesque, ought to be grafted standard high, for the same reason. For picturesque decoration in artificial scenery, all the upright shrubby and tree willows may be scattered or grouped along the margin of water; and all the creeping or trailing kinds placed on rockwork, and left to take their natural shapes. Such species of willow as S. pentándra, S. lùcida, and one or two others, from having little of the aspect common to the willow family, and, consequently, their forms not being associated with the idea of moist soil or water, may be placed near a house, or in a shrubbery or flower-garden, on account of their fragrance and early blossoms: but this cannot be recommended with respect to willows in general, which always convey the idea of the vicinity of water, or of marshy ground.
A Salictum is the only scene in which a complete collection of willows can be displayed to advantage; because, as we have already observed, willows are not trees that will associate well with any other kinds. We would by no means recommend a salictum to be formed along the margin of water where the plants can be seen only on one side; unless, indeed, the object were to form picturesque scenery. In this case, the plants may be grouped in various ways; some on the margin of water, others on the open lawn, and some on rocks, banks, and stony places. A salictum where the object is to preserve as much as possible the indigenous characters of the kinds, ought to contain various surfaces and kinds of soil; and be wholly aquatic in some places, and rocky, gravelly, sandy, or arid, in others. Such a salictum is admirably adapted for hilly countries; and, as almost all the willows are natives of cold climates, a salictum of this kind would be a scene particularly suitable for the north of Scotland. A gardenesque salictum is that which would produce most effect in a fertile and level country; and, if water is at command, it may either be conducted in drains under the surface, for the purpose of irrigation at pleasure; or it may appear in a canal, surrounding the salictum, and assuming a gardenesque or artistical form; or in a geometrical or gardenesque pond in the centre. In such a salictum, all the plants ought to be placed singly, with an ample space between them to allow each to attain its natural size and shape. The creeping and trailing sorts ought also to be planted singly, and allowed free space to extend themselves on every side; because, here, the object being more to display botanical character in a gardenesque manner than to exhibit the curious gardenesque, it would hardly be proper to graft the creeping and trailing sorts standard high, so as to make trees totally different from any ever seen in nature.
As all the species of Salix flower in early spring, or from the beginning of March to the middle of June, and as the flowers are, in the daytime when the sun shines, covered with bees, the salictum is one of the most cheerful and inviting of garden scenes after the gloom of winter has passed away. For this reason, it is desirable that the soil of the salictum should be dry at
that season, in order that the walks may be used without the risk of damping the feet. For the same reason, also, when it can be accomplished, the salictum should not be at any great distance from the shrubbery or the flower-garden. Let us suppose a collection of a hundred sorts of willows, planted in good soil, with sufficient room to assume their natural sizes and shapes; that the plants have been ten years planted; and that they are all in flower, or coming into flower; and we shall readily imagine that a scene of so much of a particular kind of beauty and splendour has never yet been presented to the botanist or the lover of gardening. For such a salictum, two or three acres would be requisite; but these, we should think, might easily be spared in the parks of wealthy proprietors in England, or in the grounds of gentlemen having residences in the mountainous districts of Wales and Scotland.
Accidents, Diseases, and Insects. The willow is subject to few accidents or diseases; but it is liable to be attacked by many insects. Salix frágilis Mathew states to be subject, in Scotland, to a disease similar to what the canker is in the apple tree. This disease, he says, is generally concentrated in certain parts of the bark and alburnum of the trunk; a portion of the branches above which withers, and the uppermost boughs, after a time, assume the appearance of a stag's head and horns; which, from the indestructibility of these dead branches, the tree retains for many years; and hence the name of stag's-head osier, which is applied to this species. This disease, and other causes, especially in old trees, give rise to rottenness in the trunk; which, in the willow, from its being comparatively a short-lived tree, takes place, more especially in wet soils, much sooner than in most other species. Mr. Sang mentions (Kal., p. 527.), that he found lime produce canker in the twigs of basket willows; so that, when he attempted to bend them, they broke short off at the cankered place. (See p. 1469.)
One of the earliest notices of insects injurious to willows is given by Mr.William Curtis, in vol. i. of the Linnæan Transactions, published in 1791. This article we consider so interesting and instructive, that we shall here give it almost entire. It was read before the Linnæan Society in November, 1788:-" Several species of willow, particularly three of the most useful and ornamental, the S. álba, the S. frágilis, and the S. babylónica, are well known to be subject to the depredations of numerous insects, and of the larvæ of the Cóssus Lignipérda (already described as attacking the elm, see p. 1386.) in particular, which feed on the substance of the wood, and prove uncommonly destructive to the latter species; for, as the larvæ in each tree are generally numerous, in the course of a few years they destroy so much of the trunk, that the first violent gale of wind blows down the tree. So infested are the weeping willows, in many nurseries, with these insects, that scarcely one in ten can be selected free from them." The willows are infested, also, in the same way by the larvæ of the Cerambyx moschàtus; and also by those of a species of the Curculionidæ, which was little suspected of committing similar depredations, but which, in proportion to its size, is no less destructive than those of the Cerambyx and Cóssus. The larvæ of a species of Nitídula [Silpha L.] are also found to be injurious in a similar manner to those above named.
In the beginning of June, 1780, Mr. Curtis observed a young tree of the Salix viminalis, which had been planted in his garden two years, and which was about 6 in. in diameter, throwing out from various parts of its trunk a substance somewhat resembling sawdust, which fell at its base in no inconsiderable quantity. This substance, on a closer examination, was found to proceed from holes about the size of a goose-quill, penetrating deeply into the substance of the wood, obliquely upwards and downwards. On its first coming out, it appeared of the colour of the wood, and was moist; and as it grew dry it became of a browner colour. The whole of the trunk where this internal operation was going forward emitted a smell somewhat like beer in a state of fermentation; and various insects, allured thereby, settled on the tree, and seemed eagerly to imbibe nourishment from it: among others, the Vanessa Atalanta, Cetonia auràta, Apis mellifica, Cántharis [Teléphorus] lívida, with
various species of Múscæ, were frequent attendants. On the 10th of June, Mr. Curtis took the Cerambyx moschatus on the trunk, but saw only one. "These extraordinary appearances," Mr. Curtis continues, "strangely excited my curiosity; I therefore often visited the tree, and, on minutely examining its bark, I discovered several small coleopterous insects in its crevices, which at first, from their great similitude, I mistook for the Cimex lectulàrius: a more close inspection, however, soon convinced me that it was Silpha grisea [Nitídula grísea Fab., &c.]. On examining the sawdust-like substance in its moist and fermenting state, I discovered many small larvæ feeding amongst it, which, when fully grown, were about a barleycorn in length; the body somewhat flattened, of a dirty white colour, having 6 fore feet and 2 hind ones; the head of a brightish brown colour, furnished with two jaws; each joint of the body projecting at the sides, so as to give it a kind of serrated appearance; the neck of a blackish brown colour, with two or more rows of small dots running therefrom down the back to the tail, which was terminated by four small setæ, turning a little upwards, the two lowermost by much the longest. The larvæ were generally found in considerable numbers together, and, on being disturbed, ran pretty briskly. From their size, and other concurring circumstances, I had no doubt but they were the larvæ of the Silpha grísea, feeding on the spoils of the tree's grand internal enemy, Cóssus Lignipérda." Mr. Curtis, being determined to get a sight of the N. grísea, with a hatchet chopped out a piece of the tree, sufficient for the discovery; when the large maggots represented in fig. 1288. at a, b, were found in perpendicularly cylindrical cavities, corroding the substance of the wood: they were
about twice or thrice as large as the maggot of the hazel nut, and very much resembling it in shape; of a yellowish white colour, gross body, apparently without any legs, having a shining head of a chestnut colour, armed with strong jaws.
On the 25th of July, cutting out a piece more of the tree, Mr. Curtis "discovered several Silphæ [Nitídulæ] as represented in fig. 1289.; and, at the same time, found on the bark of the tree the Curculio [Cryptorhynchus Illig.] lápathi (fig. 1288. d, e); and, on cutting further into the tree, found the same species just broken forth from its pupa (c)." Mr. Curtis "was then satisfied that all the mischief which had been done to the tree was effected by this species of Curculionidæ," viz. C. lápathi (d, e); and which he "had some years before found in great plenty on the leaves of the same species of Salix," viz. S. viminalis. Having succeeded in discovering the principal circumstances of the history of this insect, Mr. Curtis was not a little anxious to find the Nitídula in its pupa state; and, after searching for it in vain on, and under, the bark of the tree, "I found," he says, " plenty of them under the surface of the ground, among the moist earth and sawdust, and several, also, of the same insect in its perfect state. I had no opportunity of observing in what manner the female Curculio lápathi deposited her eggs: most probably they are laid under the bark at first, or in some crack or crevice of the tree, arising from an injury; at least, that is the mode in which the female Cóssus Lignipérda deposits its eggs, and to prevent which, we cannot be too much on our guard; for, if the larvæ have once entered the tree, we shall in vain seek a remedy. If the tree, therefore, sustain any injury from lopping, or from any other cause, a piece of canvass, spread over with some adhesive resinous substance, should be applied to the wound; or the nurseryman may find his account in matting over the bodies of his young trees during the months of June and July, when the moth comes out of its chrysalis; or,
perhaps, brushing them over at that period with some coal tar " may, by its smell, which is known to be offensive to all insects, deter any from settling on the trees for some days or weeks. In fig. 1289., f shows the larvæ of Nitídula
grísea; g, one of the same larvæ magnified; h, the pupa of the Nitídula grisea; i, the pupa magnified; k, the perfect insects; and 1, the perfect insect magnified. (Lin. Trans., vol. i. p. 89.)
Cryptorhynchus lápathi is exceedingly abundant in the osier beds near Barnes and Mortlake. In the perfect state, it is very sluggish, remaining nearly stationary upon the leaves and slender twigs, to which it attaches itself very firmly, by means of its broad cushioned tarsi, and probably, also, by the bent hook at the extremity of the tibiæ. Several interesting particulars are recorded relative to this species in Howitt's Book of the Seasons. In the late Mr. Haworth's Review of Entomology, published in the first part of the old Entomological Society's Transactions, is given an extract from the Ashmolean Appendix to Ray's Historia Insectorum, relative to the "Curculio lápathi of Linnæus, the ancient spelling of which appears to have been Gurgulio; which species was selected for two reasons; "the one, because it is a well-known insect; and the other, because, according to this ingenious author, it possesses, though feebly, the faculty of voice; which is a piece of information for which I am altogether indebted to this tract." "Lacessitus vocem quærulam dedit." The sound here alluded to is produced by the friction of the hollowed base of the thorax against the elevated front of the elytra.
This insect, which is the Curculio lápathi of Linnæus (Syst. Nat., ii. 608. 20.; Rhynchæ'nus lápathi of Fabricius, Syst. Eleuth., ii. 466., and Gyllenhall and the Cryptorhynchus lápathi of Illiger and Stephens), varies in length from in. to in. It is of an opaque dirty black colour, with the sides of the thorax, and the base and apical portion of the elytra clothed with white scales; the thorax and elytra being also ornamented with minute tufts of black scales. It feeds, also, upon the alders and sharp dock (Rumex acutus), according to Gyllenhall. Kirby and Spence, however, appear to doubt the correctness of this last habitat, considering the name lápathi to have been given to the insect by mistake; observing that, as "docks often grow under willows, the mistake in question might easily have happened." (Introd. to Ent., i. p. 196. note.)
In the salictum in the Botanic Garden at Oxford, we are informed by Mr.
Baxter, several of the species are in some seasons almost entirely destroyed by the Cryptorhynchus lápathi. Mr. Baxter, jun., informs us that the species of willow which are least injured by this insect are, the S. pentandra, S. decípiens, and S. nígricans. After the wood in the trunk of the tree is partially destroyed, it is generally found infested by the black ant (Formica fuliginosa Latr.), which is found, not only in the wood of the willow, but in that of other decayed trees, even in houses, living on the decayed rafters and wooden floors. In Kirby and Spence's Entomology, these insects are described as living in societies, and "making their habitations in the trunks of old oak or willow trees, gnawing the wood into numberless stories, more or less horizontal, the ceilings and floors of which are about five or six lines asunder, black, and as thin as card; sometimes supported by vertical partitions, forming an infinity of apartments, which communicate in some places by small apertures; and at others by light, cylindrical pillars, furnished with a base and capital, which are arrayed in colonnades, leaving a communication perfectly free throughout the whole extent of the story." (Kirby and Spence's Introd., &c., i. p. 483.)
By far the most valuable species of willow in English woods, as already stated, is S. càprea; and on this the Trochílium crabronifórme, or lunar hornet sphinx, feeds, in its larva state, upon the living wood, by boring into the trunk, and thus destroying the tree. An account of this insect has been communicated to the Magazine of Natural History by the Rev. W. T. Bree, of which we give the following abstract:-"In the Transactions of the Linnean Society, vol. iii. tab.i., a figure of the Tro
chílium crabronifórme (fig.1290.), under the name of Sphinx crabronifórmis, is given in its three stages. Lewin, the writer of the article, gives it as his opinion that 'the caterpillar does not enter the
wood till the second year of its own age;' and he states as a reason, that, among all the numerous larvæ he has found from June to November, he could perceive but a slight difference in size. Possibly, therefore, they may feed on the tender bark of the sallow root the first year after they are hatched." This, Mr. Bree thinks, is very probably the case; for he adds that he has not observed in the wood any perforations of a very small size, or such as have the appearance of having been made by caterpillars newly hatched. As the caterpillar eats its way upwards through the solid wood, a question may arise: How is the sphinx, when it bursts from the chrysalis, to make its escape out of the wood without injury? To obviate this difficulty, instinct directs the caterpillar, before it changes to a chrysalis, to turn its head downwards, so as to be opposite to the orifice, which affords a ready exit for the winged insect. A portion of the plate in the Linnæan Transac tions above referred to is copied in fig. 1290.; in which a is the male imago, or perfect insect; b, the female imago: and in fig.1291.; in which c is the larva, or caterpillar, in its proper situation, with its head upwards, in the act of feeding on the wood; d, the pupa, with its head downwards, preparatory to its exit; and e, the web closing the orifice by which the larva had entered, and by which the imago must come out. Mr. Bree sent us the butt ends of three young willow trees, which had been perforated by the insect, as shown by a view of their ends given in fig. 1292. One of these, on being split up, presented the appearance of fig. 1292. a; and, as it did not then include the case of the pupa, we conclude that the insect had escaped. The insect enters the stems, which it perforates near the root, and eats its way upwards for several inches, sometimes to the length