Alnus glutinosa Aurea - Common alder, Black alder, European alder

Alnus glutinosa 'Aurea' is a form of Common Alder or Black Alder, characterised by moderate growth and particularly bright foliage, yellow-orange in spring turning to golden light green in summer. Its brown branches bear numerous pendulous male catkins, ranging from yellow-green to brown, from March, alongside discreet female catkins. Suitable for moist soils and medium-sized gardens, this elegant small tree also has excellent resistance to diseases and pests.

Alnus glutinosa 'Aurea' is a variant of the common alder. In harsh climates and poor, marshy, and oxygen-deprived soils, Common Alder, with its rot-resistant and lightweight wood, reigns supreme. This deciduous tree belongs to the Betulaceae family and is widespread in the native flora of Europe, extending to Scandinavia. It is sometimes referred to as "vergne" or "verne". The 'Aurea' cultivar, from which it originates, is distinguished by the colour of its foliage. It is a small tree with a dense pyramidal habit, reaching a height of 8 to 10 m and a spread of about 4 m. Its growth rate is rather slow. The leaves are slightly sticky to the touch, especially on juvenile leaves. The buds are purple and also sticky, particularly in winter. The oval-shaped leaves can reach up to 8 cm in length, with a rounded yip. The young spring leaves are coloured yellow-orange and then greenish in summer. Flowering takes place in March. Each tree bears discreet female catkins and pendant male catkins, reaching 6-7 cm in length, with a brown-yellow colour. The fruits are small 2 cm long cones called strobiles, which appear from September onwards and remain on the branches for a long time. Each cone contains tiny winged fruits that will be dispersed by the wind. This tree retains its foliage for a long time in autumn. It has a deep root system, which allows it to resist wind and flooding.

As a pioneer species, loving water from any source, the Common Alder and its varieties are used as solitary trees, in tree lines, in groves, or to retain banks along streams, natural ponds, or in damp, acidic soils of humid 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. To accompany the 'Aurea' Common Alder, for example, choose a Nyssa sylvatica and Bald Cypress (Taxodium distichum), which require similar growing conditions. Two fern species can also be planted at its base, such as Sensitive Fern, in neutral to acidic and moist soil, in full sun or partial shade, and Marsh Fern (Dryopteris palustris). A luminous small tree, ideal for riverside or marsh scenes, in light shade or full sun.

The Common Alder is also a utilitarian 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 alder wood piles.