The common laburnum seldom exceeds 30 feet in height. The largest I have seen stands in the laundry yard of Alnwick Castle, over 40 feet high, wide-spreading, with a double stem measuring over 11 feet in girth near the ground. When Loudon measured it in 1835 the girth was only 6 feet 11 inches. It is a magnificent sight when in bloom. The timber of laburnum, though now greatly neglected in favour of foreign woods, is of admirable quality for cabinet work, being of a dark olive tint, and taking a fine polish. Seeing that the laburnum is perfectly hardy in our climate and grows rapidly in any well-drained soil, it seems a pity that the fine material it produces is not more commonly used.
FLOWER OF LABURNUM
The alpine laburnum (L. alpinum) goes by the name of Scottish laburnum in the nursery trade. Like the common laburnum, it is a native of Central Europe, being, probably, merely the mountain form of the other, to which it bears a strong general resemblance. The readiest means of distinguishing between the two species consists in the foliage and young shoots. In the common laburnum the leaf stalks, young shoots, and under sides of the leaves are thickly clothed with a smooth, silky pubescence, whereas in the alpine species these parts are quite bare, which causes the tree when in leaf to appear of a deeper green than the other. But the important difference for planters is that the alpine laburnum blossoms a fortnight or so later than the common laburnum, thereby prolonging the display of these charming trees. Elwes describes the flowers of the alpine laburnum as being paler in colour than those of the other species; but according to my own observation they are of the richer gold. There are some fine specimens in the Edinburgh Botanic Garden, verging upon 100 years old, about 40 feet high, and now past their prime. The timber is of the same fine quality as that of the common laburnum.
Some beautiful hybrids have been reared between these two species, and planters cannot be too strongly recommended to use them. The variety known as L. watereri bears flower-tassels 15 to 18 inches long. As it is propagated by grafting on the common species, care should be taken not to allow the stock to overcome the scion, root suckers and stem spray being rigidly suppressed.
Another curious hybrid is L. adami, which originated nearly a hundred years ago in a French nursery through engrafting Cytisus purpureus on a laburnum stem, with the result that this graft-hybrid produces yellow flowers on some branches and violet ones on others.
Mr. Gerald Loder has secured a charming effect at Wakehurst Place, Sussex, by planting wistaria to grow with laburnum, the flower racemes being similar in size and shape, but respectively of the complementary colours, yellow and violet.
In writing of a beautiful tree as the false Acacia, no reflection upon its integrity is implied in the epithet. The Robinia is so called because Englishmen have chosen to call it an acacia, which it is not, any more than it is a locust tree, as the Americans speak of it. Its scientific title is Robinia pseudacacia, commemorating Jean Robin, who first reared it in France in 1601 from seeds sent to him from North America, where it is very widely spread and much valued for the durability of its timber.
William Cobbett (1762-1835) conceived an extravagant idea of its merits, and predicted that it would supersede all British trees, including the oak; but this expectation has fallen far short of fulfilment. Among many other landowners who were induced to act on the faith of it, Lord Folkestone, a fellow-Radical of Cobbett's, planted 13,000 or 14,000 locusts at Coleshill Park, Berkshire, in 1824; but of these only very few remain now, none of them over 60 feet high. The fact is, the Robinia loves more sun than it gets in most parts of our islands and a hotter soil. This renders it unsuitable for planting in Scotland, especially in the humid west. There are, indeed, a few large specimens north of the Tweed, such as one at Cordale House, Dumbartonshire, 64 feet high by 7 feet in girth; another at Mauldslie Castle, Lanarkshire, 60 feet high by 8 feet 7 inches in girth; and, most northerly of all, one at Gordon Castle, which in 1904 measured 56 feet high by 9 feet in girth. But, as a rule, it is only to be found in good form in the sunnier shires; besides, notwithstanding the strength of its timber when felled, the growing boughs are exceedingly brittle, which makes the tree unsuitable for exposure to high winds.
