Quercus sideroxyla - Trees and Shrubs Online

New growth on Quercus sideroxyla (Yorkshire Arboretum, UK, 8 May 2025). Image John Grimshaw.

Tree to 20 m tall and 45 cm dbh, sometimes shrubby, young shoots tomentose. Leaves evergreen, leathery, oblanceolate, to obovate, 4–9 × 1.5–3.5 cm, apex rounded to bluntly pointed, base rounded or slightly heart shaped, margin slightly revolute with up to 6 teeth on each side of the midrib ending in short bristle tips, more deeply toothed on vigorous shoots. They are glossy dark or bluish green and more or less glabrous above with up to 9 impressed veins on each side of the midrib, beneath with a thin white or yellowish tomentum that covers the leaf surface but leaves the veins visible. Petioles pubescent, to 8 mm long. Fruit borne singly or in pairs on a short peduncle to 5 mm long. Cupules hemispherical, to 10 × 17 mm, acorns ovoid, to 15 × 12 mm, ⅓ to ½ included in the cup and ripening the first year. (Pérez Mojica & Valencia-A. 2017; Bonpland 1810).

Distribution Mexico Aguascalientes, Chihuahua, Coahuila, Durango, Guanajuato, Jalisco, Michoacan, Nayarit, Nuevo León, Queretaro, San Luis Potosi, Sonora, Tamaulipas, Zacatecas.

Habitat Pine/oak forest, 1650–2800 m asl with pines, other oaks, Alnus, and Arbutus.

Conservation status Least concern (LC)

Introduced by Francisco Garin from Sierra Tarahumara, Chihuahua, Mexico, in 2008. There are six plants at Iturraran Botanic Garden, Spain, where the largest was about 8 m tall in 2021 (F. Garin, pers. comm.). A plant grafted from one of the Iturraran trees is at Arboretum du Passadou, France. The species was later collected from Chihuahua by Béatrice Chassé in 2010. Planted in 2011, it reached 9 m × 16 cm in 2021 at Arboretum des Pouyouleix, France, and has fruited there since 2020 (B. Chassé, pers. comm.). Another introduction by Béatrice Chassé, from Coahuila and originally thought to be Q. scytophylla, is at Arboretum des Pouyouleix and Thenford House, Northamptonshire, UK.

The epithet derives from the Greek for iron wood: σίδηρος (sídēros) = iron + ξύλον (xúlon) = wood. Bonpland (1810) described it as having ‘ligno durissimo’ (very hard wood).

Foliage of the Quercus sideroxyla at Arboretum Chocha, France, in June 2023, showing the tomentose leaf undersides. Image Michel Duhart.

Trunk of Quercus sideroxyla at Arboretum Chocha, France, in June 2023, where it was grown as Q. coahuilensis. Image Michel Duhart.

Quercus sideroxyla foliage at Arboretum Chocha, France, in June 2023. Image Michel Duhart.

Leaf undersides of Quercus sideroxyla at Arboretum des Pouyouleix, France, October 2021. Image © Koen Camelbeke, Arboretum Wespelaar.

The dark green leaves of Quercus sideroxyla are typically toothed towards the apex. Thenford House, Northamptonshire, UK. September 2021. Image Maricela Rodríguez.

Quercus sideroxyla he leaves have a distinct, thin, silvery white tomentum beneath. Thenford House, Northamptonshire, UK. September 2021. Image Maricela Rodríguez.

The leaf veins are distinctly impressed on Quercus sideroxyla. Iturraran Botanic Garden, Spain, July 2017. Image Francisco Garin.

On the lower leaf surface of Quercus sideroxyla, the veins stand out against the pale tomentum. Iturraran Botanic Garden, Spain, July 2017. Image Francisco Garin.

Vigorous shoots of Quercus sideroxyla can have deeply toothed leaves. Iturraran Botanic Garden, Spain, July 2017. Image Francisco Garin.

A vigorous Quercus sideroxyla at Arboretum des Pouyouleix, France, in August 2021. Image Béatrice Chassé.

The tomentum on the leaf undersides of Quercus sideroxyla does not hide the veins. Arboretum des Pouyouleix, France, August 2021. Image Béatrice Chassé.

Quercus sideroxyla leaves are dark green above with somewhat impressed veins. Arboretum des Pouyouleix, France, August 2021. Image Béatrice Chassé.

An acorn forming on Quercus sideroxyla at Arboretum des Pouyouleix, France, in August 2021. Image Béatrice Chassé.

Quercus sideroxyla leaves are slightly revolute with shallow teeth towards the apex. Arboretum de Passadou, France, July 2021. Image Jean-Louis Hélardot.

Sharply toothed leaves on Quercus sideroxyla at Arboretum du Passadou in July 2021. It was grafted from a plant at Iturraran Botanic Gardens that was grown from seed collected in Chihuahua, Mexico, in 2008. Image Jean-Louis Hélardot.

Quercus sideroxyla Bonpl.

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