Alnus glutinosa Greenwood - Black alder

'Alnus glutinosa 'Greenwood', also known as Common Alder or Black Alder, is a variety that stands out for its twisted habit. Its branches are twisted, and sinuous, very similar to the undulating branches of the twisted willow. Its brown twigs are adorned from March onwards, before the foliage, with numerous yellowish-green to brown pendulous catkins that are highly decorative. Suitable for small gardens, this very elegant small tree also withstands diseases and pests very well. It excels in waterlogged and poor soils, where it is sometimes the only one able to grow.

In harsh climates and poor, marshy, and suffocating soils, the Common Alder, with its rot-resistant and lightweight wood, reigns supreme. This deciduous tree, belonging to the Betulaceae family, is widespread in the native flora of Europe, up to Scandinavia. It is sometimes called the alder or black alder. The 'Greenwood' variety was selected by J. Mauritz in Opheusden, Netherlands, in 2005. It is mainly distinguished by its twisted branches. It is a small tree with a pyramidal and airy habit, reaching a height of 5 to 6 m at maturity with an approximate spread of 3 m. Its growth is rather slow. Its foliage is light green and vibrant, even lighter underneath and slightly sticky to the touch, especially the young 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, dispersed by the wind. This tree retains its foliage for a long time.

As a pioneering species, loving water from any source, the Common Alder is used as a solitary tree, in groups, or to retain banks along streams, natural pools, or in waterlogged and acidic soils of damp undergrowth. It should be kept away from foundations and buildings, as its extremely developed root system (up to 4 m deep) is capable of obstructing drinking water pipes. Plant the 'Greenwood' Common Alder with shrubs or trees with similar requirements, such as Nyssa sylvatica or 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, ideal for riverside or marsh scenes, in light shade or full sun.

The Common 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 the construction of underground water pipes and channels. A large part of the city of Venice is said to have been built on piles made of Alder wood.