The Alpine laburnum (Laburnum alpinum) belongs to the Fabaceae family, also called Leguminosae, and is a woody plant with an arboreal or shrubby habit, which can reach 6 m in height. The trunk has a smooth greenish-brown bark with numerous lenticels, which over time turn white with lichens. The twigs are ascending and flexible, dark green or olive green when young, glabrous or with few silky hairs. The wood clearly smells of vegetables. The buds are scattered, close together, first small and pointed, then pointed and brown. The roots are strong, fine, sucking and form the classic symbiosis typical of legumes with nitrogen-fixing bacteria. The leaves are compound, trifoliate, borne on brachyblasts, with long petioles. The elements that constitute them are elliptical, pointed, with light green upperside and paler underside, but both glabrous except below on the midrib (unlike Laburnum anagyroides, the common Laburnum). The leaf margin is complete and often wavy. The hermaphroditic flowers that appear from May to July are very fragrant, abundant, gathered in dense, hanging clusters up to 30 cm long. Golden yellow in color, carried by individual hairy peduncles, have a corolla of 13-15 mm without reddish spots in the center of the flag (but a slight trace is sometimes visible). Pollination is entomophilous. The fruits are flat, glabrous legumes, 30-50 mm long and 8-10 mm wide, with a 1-2 mm wing on the dorsal margin. They contain 1 to 5 brown seeds each. The plant containing a toxic alkaloid (cytisine with paralyzing and in some cases fatal action), in all its parts but especially in the seeds, its cultivation is not recommended in public places frequented by children. Despite this, deer can safely eat its leaves, while rabbits and hares eat its bark with no problem.
Climate and relief
Alpine Laburnum is present in all regions except Puglia, Sicily and Sardinia. In Lazio, his presence is uncertain. It is a rare plant in the Apennines, growing on any substrate from 500 to 1800-2000 m above sea level. It resists lower temperatures than the common laburnum, prefers the cool and humid forests of the mountainous zone, and is generally accompanied by beeches. It is a heliophilous species, which however in very hot climates it is good to expose in partial shade. The average annual rainfall required by the plant should not be less than 800/900 mm.
Plant and cultivation techniques.
Alpine Laburnum is a frugal plant, growing successfully even along ravines punctured by avalanches. Its strong suction capacity contributes to this, so it is used to reinforce slopes and irregularities. Its presence enriches nitrogen-poor soils. It prefers moist and cool soils, if possible slightly calcareous, but it adapts very well in this direction. Propagation is done by seed in spring or autumn, cultivars or hybrids are rather propagated by cuttings or grafting (grafting is done at the end of winter). In turn, it is used as rootstock for other legume species. Planting is done with seedlings or grafts indiscriminately, since the root system is not a taproot. Cultivation is generally very easy. Pruning is not even necessary, except in the presence of damaged or crossed and therefore unsightly branches. Florists grow it in greenhouses to force it to bloom at the end of winter. In medium to small gardens, it stands out well against a dark, evergreen background of evergreens, growing close to a wall or used as a living support for a simultaneously flowering wisteria. It can be grown in arches to create pergolas or covered walkways, or in pots, especially the smaller ‘Pendula’ variety. grown close to a wall, or used as a living support for a wisteria which blooms at the same time. It can be grown in arches to create pergolas or covered walkways, or in pots, especially the smaller ‘Pendula’ variety. grown close to a wall, or used as a living support for a wisteria which blooms at the same time. It can be grown in arches to create pergolas or covered walkways, or in pots, especially the smaller ‘Pendula’ variety.
Among the diseases of Laburnum, which is still a very resistant plant, we distinguish the mosaic virus, with leaves showing chlorotic spots, followed by the appearance of yellowish bands in the veins, and white mold. Some specimens are affected by root rot, especially in too wet soils. Although it is a poisonous plant, it can be attacked by pests, including aphids, and moth larvae, including Phalera bucephala, can feed on its leaves.