Alnus glutinosa Laciniata - Black Alder

'Alnus glutinosa 'Laciniata', also known as the Cut-leaved Alder or Black Alder, is a variety with deeply cut foliage, slightly smaller than that of the species. The slightly toothed lobes are lanceolate and less cut than those of the cultivar 'Imperalis'. Its brown branches are adorned, from March onwards and before the foliage appears, with numerous, very decorative, pendulous, yellow-green to brown catkins. This medium-sized tree also has a graceful habit with slightly drooping branches. Therefore, it needs more space to thrive and excels in waterlogged and poor soils, where it is sometimes the only plant that can grow.

In harsh climates and poor, marshy, and suffocating soils, the Black Alder, with its rot-resistant and lightweight wood, reigns supreme. This deciduous tree from the birch family is very common in the native flora of Europe, up to Scandinavia. It is sometimes called "vergne" or "verne". The 'Laciniata' variety is mainly distinguished by its deeply incised leaves. It is a small tree with a pyramidal and airy habit, with drooping branches, reaching a height of 8 to 12 m at maturity with a spread of about 5 m. Its growth is rather slow. Its foliage is light green and vibrant, even lighter underneath, and slightly sticky to the touch, especially the juvenile leaves. The buds are purple and also sticky, especially in winter. The spring inflorescence is a kind of small cone called a strobilus, 2 cm long, containing tiny winged fruits that will be dispersed by the wind. This tree retains its foliage for a long time.

As a pioneering species that loves water, regardless of its source, the Black Alder is used as a standalone tree, in groups, or to retain banks along streams, natural ponds, or in waterlogged, acid-prone soils in damp woodlands. It should be kept away from foundations and buildings, as its extensively developed root system (up to 4 m deep) is capable of obstructing water pipes. Plant the 'Laciniata' Black Alder with shrubs or trees that have similar growing conditions, such as Nyssa sylvatica or the Bald Cypress. At its base, plant ferns like Onoclea sensibilis, in neutral to acidic and moist soil, in full sun or partial shade. An elegant small tree, perfect for riverside or marsh scenes, in dappled shade or full sun.

The Black Alder is also a useful tree, used in forests to prepare and improve the soil before planting poplars. Considered a green manure by foresters, it purifies and enriches the soil in which it is planted, as its roots convert atmospheric nitrogen into plant proteins. Its wood, almost rot-resistant in water, was once used for underground water pipes and channels. A significant part of the city of Venice is said to have been built on piles made of Alder wood.