There is but one precaution to be observed in planting laburnums--namely, that they should not be within reach of horses or cattle, for the seeds contain a powerful poison called cytisine. Some years ago, wishing to do wayfarers a service by enlivening a stretch of high road, I caused a row of laburnums to be planted on either side. The trees had attained some stature, when a Clydesdale mare belonging to the tenant of a field bordering the road suddenly died, her death being attributed to eating laburnum seeds, so the trees had to be uprooted. Neither leaves nor bark appear to contain the poison, judging from the avidity shown by rabbits in devouring them. No tree is so vulnerable _at all ages_ by those detestable creatures as are the laburnum and the holly. The largest stems are liable to be barked by them in hard weather. Some writers have copied Pliny in stating that bees will not visit the flowers of laburnum; but Pliny cannot have been writing from personal observation, for modern bees, at least, show no aversion to the yellow blossoms.
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.
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.