The Trees of Great Britain & Ireland/Volume 1/Ailanthus

by Henry John Elwes and Augustine Henry

 

AILANTHUS

 

Ailanthus, Desfontaines, Mém. Acad. Paris, 1786 (1789), 263, t. 8; Bentham et Hooker, Gen. Pl. i. 309 (1862); Prain, Indian Forester, xxviii. 131, Plates i. ii. iii. (1902).

 

Lofty trees with very large alternate imparipinnate leaves. Flowers small, polygamous, bracteolate, in panicles. Calyx 5-toothed, imbricate. Petals 5, valvate, disk 10-lobed. Stamens 10 in the staminate flowers, 2–3 in the hermaphrodite flowers, and absent in the pistillate flowers. Ovary present in pistillate and hermaphrodite flowers, rudimentary in staminate flowers, deeply 2–5 cleft with connate styles: ovules 1 in each cell. Fruit of 1–5 samaras, with large membranous wings, each samara containing 1 seed.

Ailanthus belongs to the Natural order Simarubeæ, and consists of about eleven species occurring in India, Indo-China, China, Java, Moluccas, and Queensland. Most of the species are tropical trees, Ailanthus glandulosa being until lately the only species which was known to occur in temperate regions; but Ailanthus Vilmoriana, Dode,^[1] must be here mentioned. This is a tree remarkable for its prickly branchlets, of which only one specimen is known, namely, a young, healthy, vigorous tree grown in M. de Vilmorin's garden at Les Barres.^[2] It was raised from seed sent by Pere Farges in 1897 from the mountains of Szechuan in Central China;^[3] and is certainly a very distinct species. I saw it in the summer of 1904, and in general aspect there is little to distinguish it from the common species. It is now about 20 feet in height. The leaflets in this species are less abruptly acuminate, not falcate, much duller above and paler beneath, with larger glands than in Ailanthus glandulosa. All the parts of the tree are much more pubescent than in that species.

Ailanthus grandis,^[4] Prain, a new species from Sikkim and Assam, which attains 120 feet high, may be here mentioned, as it is possible that it might be grown in Cornwall or in Kerry. It has not yet been introduced.

 

 

AILANTHUS GLANDULOSA, Ailanthus Tree

 

Ailanthus glandulosa, Desfontaines, Mém. Acad. Paris. 1786 (1789), 263, t. 8; Loudon, Arb. et Frut. Brit. i. 490 (1838); Britton and Brown, Illustrated Flora of the Northern United States and Canada, ii. 355, Fig. 2272 (1897).

 

A tree attaining 100 feet in height and 13 feet in girth; branches massive and forming an oval crown, which becomes flattened at the top in old trees. Bark smooth, grey, or dark brown, and marked by longitudinal, narrow, pale-coloured fissures, which are very characteristic.

Leaves deciduous, compound, 1–3 feet long, imparipinnate, with 7–9 (sometimes even 20) pairs of leaflets, which are either opposite or nearly so, shining above, pale and glabrous (occasionally slightly pubescent) beneath, and unequally divided by the midrib. Each leaflet is stalked, ovate, or ovate-lanceolate, acute or acuminate at the apex, cordate or truncate at the base, entire in margin, except that near the base there are 1–4 pairs of glandular teeth. Stipules absent. The leaves appear late in spring, and exhale when rubbed a disagreeable odour which renders them distasteful to animals. They fall off late in autumn, absciss layers being formed at the base of the leaflets as well as of the main stalk; the former usually drop first.

Flowers appearing in July and August in large panicles at the summit of the branchlets, either unisexual or hermaphrodite; but as a rule the trees are practically diœcious, and those bearing staminate flowers give off an objectionable odour.

Fruit, 1–5 keys, resembling those of the ash, linear or oblong, membranous veined, with a small indentation above the middle on one side, close to where the seed is located; and the wings on both sides of the seed are slightly twisted, so that the fruit in sailing through the air moves like a screw. The keys are bright red or purplish brown in colour, and are very conspicuous amidst the green foliage.

Seedling: the cotyledons appear above the soil on a caulicle about an inch long and are foliaceous, coriaceous in texture, oboval, obtuse, shortly stalked, entire in margin, and pinnate in venation. The stem above them is pubescent, and at a short distance (about ½ inch) up bears two leaves, which are trifoliolate and longstalked, the terminal leaflet being lanceolate, acuminate, and entire, the two lateral shorter and toothed.^[5] Higher up ordinary pinnate leaves are borne. Plate 15 a shows a seedling raised by Elwes from seed ripened on a tree overhanging Dr. Charles Hooker's garden at Cirencester in 1900;^[6] sown November 26, germinated under glass in May 1901, and photographed on August 28 of the same year, when it measured about a foot high; the roots, which were very succulent and brittle, were 13 inches long. The seedlings were planted out in May 1902, and grew very rapidly, attaining 5 feet in height, but did not ripen their wood, which was killed back in some cases nearly to the ground. They are now (January 1905) 4–6 feet high.

 

Identification

In summer the Ailanthus is readily distinguished from all other trees cultivated in England by its large pinnate leaves, which have at the base of the leaflets on each side one or two glandidar teeth. The black walnut, butternut, and Cedrela sinensis have somewhat similar foliage; but in these the glandular teeth are wanting. The bark of Ailanthus is quite peculiar, and when once seen cannot be confounded with that of any other tree.

In winter Ailanthus is easily recognised by its bark in trees of a certain size; but in all stages of growth it is well marked by the characters of the buds and branchlets.

The buds are alternate, uniform in size, small and hemispherical, and show externally 2 or 3 brown tomentose scales.^[7] The buds are set obliquely on the twigs just above the leaf-scars. The latter are large, heart-shaped, and slightly concave; and on their surface may be seen about 7 little elevated cicatrices which correspond to the vascular bundles of the fallen leaves. No true terminal bud is formed; and at the apex of the twig there is an elevated small circular scar, which marks the spot where the tip of the branchlet fell off in summer. The twigs are very coarse, glabrous, or finely pubescent, shining and brown in colour, with a few plainly visible lenticels. The pith is large, buff or yellowish in colour, showing clearly on section the medullary rays. In Cedrela there is a large terminal bud, and the leafscar has 5 cicatrices. The chambered pith of Juglans will readily distinguish the black walnut and butternut.

 

Varieties

Several varieties are mentioned in books; aucubæfolia, pendulifolia, rubra, and flavescens being recognised by Schelle;^[8] but it is doubtful if any of these are sufficiently marked to deserve recognition. The Ailanthus flavescens^[9] of gardens was determined by Carrière to be Cedrela sinensis. A form with variegated leaves is mentioned by Koch,^[10] but it is exceedingly rare. The Kew Hand-list only admits one variety, pendula, a form somewhat weeping in habit.

 

Distribution

Ailanthus glandulosa has been only found truly wild on the mountains of the province of Chihli in Northern China; but it is cultivated in most parts of China, and doubtless was once a constituent of the forests of the northern coast provinces, most of which have been destroyed by the Chinese. I never saw it wild in any of the mountain forests of Central or Southern China. When first introduced into Europe it was supposed to be the species of Rhus which yields Japanese varnish or lacquer; and even now it is often called in France Vernis du Japan. The tree, however, is unknown wild in Japan, and is seldom or never cultivated there. The Chinese in classical times were well acquainted with Ailanthus, which they called ch'u, a word explained as meaning "useless wood," as it was in ancient times (as well as at present) used only for firewood.^[11] Popularly Ailanthus and Cedrela are now called ch'un trees, the former being distinguished as the "stinking ch'un," and the latter as the "fragrant ch'un,"

In China the Ailanthus grows to be a large tree; but the timber is little valued. The root-bark is used, as a strong infusion, in cases of dysentery.^[12] In the Pharmaceutical Museum, London, there are several specimens of barks bearing the Chinese name for Ailanthus; but these are doubtfully referable to that species; and the whole subject of the use of Ailanthus bark for dysentery requires further investigation.^[13]

In the Kew Museum there are specimens of silkworms (Attacus Cynthia, Drury), which feed on the leaves of Ailanthus in North China; and there are also samples of the "wild silk" produced, which is made into one kind of pongee. This species of silkworm was introduced into France in 1858; and large numbers of Ailanthus trees were planted with a view to the feeding of the silkworms. The winter of 1879 killed off all the silkworms; and apparently the cultivation of the tree in France for the production of silk is a thing of the past.

In the Kew Museum there is a note attached to a specimen of the wood of Ailanthus glandulosa from Tuscany, which says that the bark yields a resinous juice; but there is no account of such a resin from Chinese sources; and exudation from the bark has not been observed in trees growing in England or in France. In India, however, the resin, called muttee-pal, is derived from the bark of Ailanthus malabarica, and is used both as an incense and as a remedy for dysentery.

 

Introduction

Ailanthus glandulosa was first introduced from China in 1751. In Hortus Collinsonianus,^[14] p. 2, a memorandum is copied which was left by Collinson, stating: "A stately tree raised from seed from Nankin in 1751, sent over by Father d'Incarville, my correspondent in China, to whom I sent many seeds in return; he sent it to me and the Royal Society." Père d'Incarville^[15] was a French Jesuit missionary, who died at Peking in 1757. In Trans. Phil. Soc., 1757, a paper is printed, which was read on 25th November 1756, being a letter from John Ellis to P. C. Webb; and it mentions two trees which were growing, one in Webb's garden at Busbridge, near Godalming, and another in the Chelsea Physic Garden, both raised from the seed sent by Père d'Incarville. The tree is here first described as Rhus sinense foliis alatis, foliolis oblongis acuminatis ad basin subrotundis et dentatis.^[16]

 

Tree of Heaven

This name is often given to the tree in England, corresponding to the German Götterbaum. It is not the translation of any Chinese name, as has often been erroneously stated. Desfontaines' original description occurred in a rare book which has not been looked up by most writers on the tree. He was well aware that the tree came from China, but in selecting a name for the genus he took it from another species which he found figured in Rumphius' Hortus Amboinensis, v. cap. 57, tab. 132. This species, left undescribed by Desfontaines, is Ailanthus moluccana. Rumphius calls it arbor cœli, the equivalent of the native name in the Amboyna language, Aylanto, which signifies "a tree so tall as to touch the sky.""Tree of Heaven" is accordingly a translation of the name of Rumphius, and is more properly applied to the tall tropical species than to Ailanthus glandulosa, which does not attain any remarkable height.

 

Cultivation

The Ailanthus is easily propagated from seeds; but as trees bearing male flowers are objectionable on account of their odour, it is preferable to propagate the tree from root-cuttings obtained from female trees. In addition to the disagreeable odour of the male flowers, there may be some foundation for the belief prevalent in the United States that they cause stomachic disturbance and sore throat. The pollen from staminate flowers, doubtless, occasions a kind of hay fever.

The tree suckers freely from the root and to a great distance, as far as 100 feet from the parent stem. At Kew these suckers frequently appear between the tiles of the floor of one of the buildings near which an Ailanthus stands. At Oxford^[17] a root-sucker sent up a flowering shoot, and, what is more remarkable, produced simple leaves, giving some support to the idea that plants with compound foliage originated from those with simple leaves. The tree has extraordinary vitality. Dr. Masters^[17] gives an account of a tree which was cut down, the stump being left in the ground below the surface. Several years elapsed during which nothing was observed, but after about ten years suckers were seen coming up in a gravel path adjacent, and these, being traced, were found to issue from the old stump.

Ailanthus reproduces itself freely from stools, and the coppice shoots thus obtained are very vigorous.

It was long supposed that Ailanthus would succeed even on the worst soils, but this is an error. It only does well on permeable soils, which are fairly moist, and for this reason it is successfully used to cover railway and road embankments in France. It will not grow well on compact clay or on chalky or absolutely poor soils. In England it has only been planted as an ornamental tree, and it is very suitable for planting in towns, as it is not injured by smoke and is free from insect attacks and fungous diseases. Though it suckers freely, this is no objection in streets, where the pavements or wheel traffic prevents them from making an appearance. The young shoots are often killed by frost, but this only serves to keep the tree within bounds without the use of the pruning knife. The Ailanthus only makes one shoot annually, late in the spring, which continues to grow till October or November, and this is the reason why it is spring tender, as the tips of the shoots do not become properly lignified. The tree, however, bears the greatest cold in winter, and was not injured by the severe frost of 1879.

The tree produces flowers in England when it is about 40 feet high; and it fruits pretty frequently, but the seeds are often infertile.

When the Ailanthus is cut back annually, it grows rapidly and produces foliage of enormous size, suitable for the so-called tropical garden. Leaves of plants so treated have measured as much as 4 feet long and 15 inches wide.

The Ailanthus succeeds in a great variety of climates, and is planted in regions so diverse as Northern India, the United States, France, Germany, and Italy. In France it has not been successful as a forest tree, as it is not a social species, and is speedily dominated by native trees, if it survives the seedling stage, when it is sensitive to spring frosts. In warmer climates it easily regenerates by seed, and in consequence has become naturalised in many parts of Europe (as on the arid slopes of Mount Vesuvius, where it stands very well the drought), and in the United States,^[18] where it often runs wild in old fields. American writers praise the tree for the value of its wood and the rapidity of its growth, as it is said to make timber faster than any of the native trees that are used for firewood.

The wood is yellowish or yellowish green, and is not clearly distinguishable into well-marked heart and sap woods, though in old trees the centre of the stem becomes deeper in colour. The wood has a specific gravity of 0.6, and is easily worked, taking a good polish. It rives easily. It is used by wheelwrights as a substitute for elm and ash; but is inferior to these, as it does not possess their elasticity or their capability of resistance to fracture. It is said, however, to bear well alternations of dry and wet.

Mr. J.A. Weale of Liverpool, who has paid great attention to the study of timbers, and knows more about them than any one in the trade in this country, writes to us that this wood resembles that of the ash so closely in structure, that the only real difference between the two is in the large cellular compound pores which are formed in the Ailanthus, as shown in the microscopical section which he enclosed.

Elwes is assured by Prof. C.S. Sargent that it makes nice furniture, and he has a specimen from a large tree which was cut down in the Palace Gardens at Wells, Somerset, of which the timber was bought by Mr. Halliday, a cabinetmaker, for £8.

 

Remarkable Trees

The largest Ailanthus was that at Syon, which was 70 feet high in Loudon's time, and nearly 100 feet in 1880.^[19] It is now dead.

At Kew a vigorous tree is growing in the garden behind the Palace, which measures 73 feet high and 8 feet in girth. Not far off a number of Ailanthus trees of varying size, but none very large, occurs in a group, and they seem to be root-suckers; probably one of the original trees was planted in this spot in the eighteenth century.

At Milton Rectory, Steventon, Berks, there are two trees of equal height (78 feet), one girthing 9 feet 1 inch, and the other 8 feet 6 inches. Both these trees bloom freely every year, producing fruit of a bright red colour on the south side of the trees; and the seeds, as they fall in the garden near hand, produce seedlings which are very vigorous.^[20]

At the Mote, Maidstone, there are two large trees, one of which is 70 feet high and 8 feet in circumference.

At Linton Park, Maidstone, is a tree growing in a shrubbery which was nearly 80 feet high by 6 feet 6 inches in 1902.

At Broom House, Fulham, the residence of Miss Sulivan, is a tree 80 feet high, with a bole 9 feet long and 10 feet in girth, which divides into two main stems (Plate 13).

At Fakenham, Norfolk, Sir Hugh Beevor has measured a tree 75 feet by 8 feet 11 inches.

At Barton, Bury St. Edmunds, an Ailanthus which was planted in 1826^[21] measured in 1904 55 feet high, with a girth of stem of 5 feet 2 inches. Bunbury says that it is perfectly hardy at Barton, and did not suffer in the least from the severe winter of 1860. It was 3½ feet girth at 3 feet from the ground in 1862. It flowered abundantly in August of 1861, the greater part of the flowers being hermaphrodite, and a considerable number of fruits were formed, but all dropped off before coming to maturity. It fruited abundantly in 1868. Bunbury says, generally there is only one samara to each flower, but not unfrequently two or three; he never saw more than three.

At Belton Park, the seat of Earl Brownlow, is a fine specimen of the tree, for a photograph of which (Plate 14) we are indebted to Miss F. Woolward, who gives its height as 83 feet, and its girth as 6 feet. This seems to be the tallest tree recorded in England.

At Burwood House, Cobham, Surrey, the seat of Lady Ellesmere, Colonel H. Thynne has measured an Ailanthus 71 feet high by 10 feet 10 inches girth, which, though partly fallen down and supported by a prop, is still a fine tree.

The tree seems to require a climate which is at once both warmer and drier in summer than that of the northern and western counties of England, and we do not know of any trees of any great size now existing in Scotland, Ireland, or Wales, though Loudon states that there was one at Dunrobin Castle, Sutherlandshire, 43 feet high.(A.H.)

 

1. Revue Horticole, 1904, p. 445, fig. 184.
2. Figured in Fruticetum Vilmorinianum, 1904, p. 31; where it is called Ailanthus glandulosa, var. spinosa.
3. Mr. E.H. Wilson informs us that it is very common in the valleys of the Min, Tung, and Fou rivers, between 2000 and 4500 feet. He says that it is much more spiny in the young than in the adult state, and that it has much larger foliage than the common species. A plant is now growing at Kew, and is referred to by Mr. Bean in Gardeners' Chronicle, xxxviii. 276(1905).
4. Indian Forester, xxviii. 131, Plate i. (1902).
5. See Plate 14, fig. B.
6. As I know of no other tree in the neighbourhood this case seems to confirm Bunbury's observation that the tree in some cases is capable of self-fertilisation.—(H.J.E.)
7. A plate showing buds will appear in a later part.
8. Laubholz-Benennung, 279 (1903).
9. See article on the "Ailanto or Tree of Heaven" by Nicholson, in Garden, 1883, xxiv. 63, with figure of flowers, fruit, and foliage, and many interesting details concerning propagation, etc.
10. Koch, Dendrologie, i. 569 (1869).
11. In the Shu-Ching, it is said: "In the ninth month they make firewood of the ch'u tree."
12. On the therapeutical value of this drug, see articles by Drs. Dudgeon and Robert, in London Pharmaceutical Journal, ser. iii. iv. 890, and vii. 372.
13. The bark has been found to be an excellent vermifuge in cases of tapeworm. See Hetet, in U.S. Dispens, 15th edition, 1564.
14. Compiled by L. W. Dillwyn, and published at Swansea in 1843.
15. In Cibot, Mém. Conc. Chinois, ii. 1777, 583, d'Incarville's "Mémoire sur les vers à soie sauvage" is published, in which he speaks of the Ailanthus as the frêne puant (stinking ash) of North China.
16. In the herbarium of the British Museum there is a specimen labelled Hort. Busbridge, which is undoubtedly from the original tree. It was cut down in 1856 owing to the great amount of shade it produced near the house (Gard. Chron. 1857, p. 55). There is another specimen from Kew Gardens, 1779, showing that the tree was cultivated early there.
17. Gard. Chron. 1887, ii. 364.
18. Also in Southern Ontario. See Britton and Brown, loc. cit.
19. Garden, 1880, xviii. 629.
20. The Rev. H. Hamilton Jackson kindly sent us this information in a letter dated Dec. 10, 1903.
21. Bunbury, Arboretum Notes, 88.