A series of lectures programmed by The Kew Mutual Improvement Society at Kew Gardens in the UK. On December 5, IOS Editor and former President Béatrice Chassé will deliver as part of this series her lecture ‘Acorns as food in human history: Myth or Reality?’ originally presented during the 2015 IOS Conference at The Morton Arboretum.
Species Spotlight: Quercus crassifolia Bonpl.
|Illustration of Quercus crassifolia from Encinos de México1.
A. Twig with catkins; B. Twig with acorn; C. Fascicled stipitate trichome; D. Leaf.
Quercus crassifolia is a tree ranging in height from 4 to 15 meters, and is usually easily recognized by its leaves: stiff and leathery, glossy blackish green above, covered with a layer of pale brown hairs beneath, and with bristle-tipped teeth above the widest part of the leaf. It was first collected by Alexander von Humboldt and Aimé Bonpland on their famous five-year journey to Latin America at the cusp of the 18th and 19th centuries; the name was published by Bonpland in 1809, thus making this species one of the first Mexican oaks to be described (several species were described by Luis Née in 1801). Amongst its numerous common names in Spanish, perhaps the most distinctive is Encino chicharrón, based on the similarity between the leaves and the fried pork rinds popular in Mexican cuisine and known as chicharrones (encino is one of the generic terms for Quercus in Mexican Spanish). The epithet crassifolia derives from the Latin crassus, meaning solid, thick, or coarse (it is the origin of the English word “crass”), and refers to the thickness of the leaves.
The species is widely distributed in Central and Southern Mexico and in Guatemala, and is found in Quercus and Pinus-Juniperus forests at an elevation of 1,300 to 2,900 m in Mexico and at lower elevations in Guatemala. It is
|Young leaves on Quercus crassifolia in Chevithorne Barton, Devon, UK. Photo: ©James MacEwen.|
commonly associated with species such as Pinus patula, P. leiophylla, Q. rugosa, Q. laurina, Q. affinis, and Q. crassipes. It is in the category of Least Concern in the Red List of Threatened Species, and its wood is used for the manufacture of agricultural implements and tool handles, as structural posts in house building, and for firewood. Charcoal obtained from this species is long lasting and has good weight. According to Romero et al., the saplings are edible, after being cooked, ground, and mixed with corn; they are also an ingredient in a potion administered to women after giving birth. The bark is used to alleviate inflamed gums, to tan leather, and in the preparation of agave-based beverages.
One of the attractive features of this oak it its young leaves, which emerge densely covered in velvety red hairs and are silvery and tomentose beneath. As they mature they turn a glossy dark green, becoming coriaceous and rugose with impressed veins. The tree is deciduous or semi-evergreen in the wild, losing its leaves just before the new ones are produced, but in cultivation it appears to be evergreen. It flowers in April and the acorns ripen in May to November, in the first or second year. The acorns are ovoid and 1-2 cm long and about 1 cm in diameter, light brown, glabrous, striated, and enclosed by a hemispherical cupule to about one third of their length. The interior of the acorn cup is wooly. The bark is smooth and grey on young trees and becomes dark and deeply fissured with rectangular scales and numerous lenticels about 3 mm long.
|Young leaves and catkins on an oak in Kew Gardens, UK, recently identified as Quercus crassifolia. Photos: ©James MacEwen.|
Q. crassifolia hybridizes with several other Section Lobatae species in the wild, especially Q. crassipes to form Q. ×dysophylla (this hybrid was originally regarded as a species and some authors still maintain that status). Other less frequent hybrids are found with Q. affinis, Q. candicans, and Q. laurina.
|Leaves and acorns of Quercus crassifolia. Note the charactersitic pale brown undersides in the image on right.
Photos: ©James MacEwen.
It was introduced to Europe in 1939 by G.B. Hinton and one of the original trees survives at Caerhays Estate in the United Kingdom. Q. crassifolia is also represented at Chevithorne Barton, Jardín Botánico de Iturraran, Arboretum des Pouyouleix, and some of the best trees in cultivation are found at Hackfalls Arboretum in New Zealand, which also holds a number of its hybrids, all collected by Bob Berry in several localities in Mexico.
 S. Romero Rangel, E.C. Rojas Zenteno, and L.E. Rubio Licona. Encinos de México. Mexico City: Universidad Nacional Autónoma de México, 2015.
Amory, Michael Heathcoat. The Oaks of Chevithorne Barton. London: Adelphi, 2009.
Coombes, Allen. 735. Quercus crassifolia. Curtis's Botanical Magazine 29, no. 2 (2012): 162-69.
Beaulieu, Antoine le Hardÿ de, and Thierry Lamant. Guide Illustré Des Chênes. Paris: Éditions du 8ème, 2006.
http://oaks.of.the.world.free.fr/. Accessed January 19, 2016.
http://www.oaknames.org/. Accessed January 19, 2016.
Romero Rangel, S., E.C. Rojas Zenteno, and M. de L. Aguilar Enriquez. El Género Quercus (Fagaceae) en el Estado de México, Annals of the Missouri Botanical Garden, Vol. 89, No. 4 (Autumn, 2002), pp. 551-593.
Romero Rangel, S., E.C. Rojas Zenteno, and L.E. Rubio Licona. Encinos de México. Mexico City: Universidad Nacional Autónoma de México, 2015.