Quercus crassipes Humb. & Bonpl.

An attractive tree of medium size, Quercus crassipes is one of the better known Mexican oaks in cultivation, both as a species and as a parent – together with its etymological cousin Q. crassifolia – of the hybrid Q. × dysophylla. It is also one of the hardier ones and is found in gardens around the world. Attractive features include the bark, which is bubbly or pachydermatous when young, the columnar habit and lustrous foliage, the dense, uniform tomentum on the leaf undersides, and the leaves’ deep, reticulate venation.

It was among the first oaks of Mexico to be described, published in 1810 in Plantae Aequinoctiales, the account of plants found by Humboldt and Bonpland while on their famed expedition to the New World (1799–1804). The epithet derives from Latin crassus (‘thick’) + pēs (‘foot’, in this case peduncle). In his description, Bonpland explained the reason for the epithet: ‘J’ai donné le nom de Quercus crassipes à cette nouvelle espèce de chêne, parce que ses fruits sont supportés par un pédoncle extrêmement court et très-gros’ (I gave the name Quercus crassipes to this new species of oak, because its fruits are supported by an extremely short and very thick peduncle). He added that this was one of the rarest oaks they found in all of Mexico (‘C’est un de chênes les plus rares que nous ayons rencontré dans tout le royaume de Mexique’) (Humboldt and Bonpland 1810). In the same work, Bonpland also described the similar Q. mexicana. While the differences between the two were evidently clear to Bonpland, they have been a matter of confusion to subsequent authors.

Quercus crassipes is distinguished by the bristle tip at the apex of the leaves, secondary veins almost perpendicular to the midrib, and leaf undersides with uniform and persistent pubescence. It is similar to Q. mexicana, which differs in that the leaf underside has contorted fasciculate trichomes that produce ‘punctuations’ or dots evident to the naked eye. Other differences with Q. mexicana include the larger number of veins (up to 19, but only up to 12 in Q. mexicana), leaves more leathery and deeply veined, cupules with an inrolled margin (erect margin in Q. mexicana), secondary veins at an angle approaching 90° to the midrib (under 80° in Q. mexicana) and petioles that are usually glabrescent (pubescent in Q. mexicana). It also resembles Q. gentryi, which has leaves with sparse indumentum on the glabrescent undersides (Hélardot 2024; Romero Rangel et al. 2015).

The similarity with Quercus mexicana has in the past caused confusion. De Candolle, in his Prodromus (1864), incorrectly determined that a specimen collected by Hartweg in Tlalpujahua, Michoacán, in 1839 (no. 431), which Bentham had understood to be Q. mexicana, was Q. crassipes. He further muddied the waters by citing the name as Q. mexicana Benth. This was not correct, as Bentham had not published the name, but rather had referred Hartweg’s specimen to Q. mexicana Humb. & Bonpl. This blunder led to further confusion when later authors stated that Q. mexicana Benth. was a synonym of Q. crassipes Bonpl., for example, Elwes and Henry (1906–1913) and Govaerts and Frodin (1998).

De Candolle’s misidentification and nomenclatural missteps may have influenced Trelease’s judgment, who also mixed up the two species. According to Muller and McVaugh (1972), in The American Oaks Trelease (1924) described and illustrated both Q. crassipes and Q. mexicana from specimens of Q. crassipes, possibly because the two species were mixed on some herbarium sheets in the Humboldt and Bonpland collection. The type of Q. mexicana (Herb. Humboldt, no. 4060) is the plant that Trelease called Q. rugulosa, a synonym of Q. mexicana; Trelease applied the name Q. mexicana to plants with leaves bullate beneath, which are Q. crassipes.

Quercus crassipes was introduced to cultivation in Britain around 1839. Loudon (1838) listed it as one of a group of Mexican oaks that had not yet been introduced, but two years later it was included in a list published by Lindley (1840) of plants raised in Chiswick Garden, the garden of the Horticultural Society of London. Though many references credit the introduction to Karl Theodor Hartweg, this may be false. Augustine Henry (in Elwes & Henry 1906–1913) cited George Gordon (1840) when writing that the plant at Chiswick Garden was raised from seed collected by Hartweg near Real del Monte, but Gordon only states the seeds were “received from Real del Monte”, without specifying a source. Gordon’s article mentions several Mexican oaks growing at Chiswick Garden, some from seeds sent by Hartweg and others from seed presented to the Society by William Fox Strangways. It is not clear where Strangways obtained the seeds, but it seems unlikely that they were collected by Hartweg, as Gordon does not mention it. Quercus crasspies is likewise not listed in Bentham’s Plantas Hartwegianas (1839–1857), which describes specimens sent to the Society by Hartweg.

De Candolle’s misidentification of Hartweg’s specimen no. 431 was probably the reason Elwes and Henry cite Q. mexicana Benth. as a synonym of Q. crassipes, and this may have led Henry to affirm that Q. crassipes was introduced by Hartweg. A plant of Q. mexicana was also among the Mexican oaks growing in Chiswick Garden in 1840, which according to Lindley were all grown from seed received either from Hartweg or Strangways.

The largest tree as yet recorded in cultivation in the UK was in fact reported by Henry as the only specimen he knew of in the country at the time (1908), which he described as “an unhealthy tree” at Carclew in Cornwall, measuring 19 m × 51 cm (Elwes & Henry 1906–1913). Probably grown from Hartweg’s original introduction, it was still alive in 1933, but has since died (The Tree Register 2024). Trees currently in cultivation in the UK have not yet reached those dimensions. The largest is at Kew and measured 14 m × 28 cm in 2022, according to Kew records accessioned in 1994 and received as seed from Lady Anne Palmer, collected in Mil Cumbres, Michoacán, by her husband Bob Berry, owner of Hackfalls Arboretum in New Zealand (H. Baldwin, pers. comm.). Based on data in the Hackfalls Catalogue, which indicate the years that Berry travelled to Mexico, the seed was probably collected a few years earlier than 1994.

In Europe, it is found in Arboretum Wespelaar (Belgium), Trompenburg Arboretum and Gardens (the Netherlands), Arboretum des Pouyouleix, Arboretum des Passadou, and Arboretum de la Bergerette (France), and Iturraran Botanical Garden (Spain). The majority of these are wild sourced from Puebla, in many cases in connection with the International Oak Society’s Conference held there in 2009. At Arboretum de la Bergerette, it has grown steadily with midday shade, adopting a columnar habit and reaching 6 m in about a decade, untroubled by the climate (Haddock 2012). At Arboretum des Pouyouleix it fruited after ten years (Chassé 2016).

What may be the oldest living tree in cultivation is at the Shields Oak Grove at UC Davis in California, accessioned in 1968 from seed collected in Puebla by Lance McIntyre and Roman Gankin in 1966 (Costello et al. 2011). It also grows at Aiken, South Carolina, where it was badly damaged by late frost in 2017, at Bartlett Tree Research Laboratories and Arboretum, North Carolina, and at Armstrong University, Georgia (Russell 2017; Cameron 2015).

In the Southern Hemisphere, it is found at Hackfalls Arboretum in New Zealand, grown from seed collected in 1982 in Michoacán and in 1984 in Hidalgo and Mexico State. One of the trees had reached 20 m in 2016 and had a dbh of 0.93 cm in 2020, making it a contender for the champion tree in cultivation worldwide (Hackfalls Arboretum 2024). At San Miguel Arboretum in Argentina, it has proved to be one of the fastest-growing oaks there and displays a fine columnar habit. It was planted in 1998 from seed obtained in 1997 at the 2nd International Oak Society Conference at The Huntington Botanical Garden in California, probably sourced from Louise Wardle de Camacho Botanical Garden in Puebla (Cameron 2016; P. Laharrague, pers. comm.).

In Mexico it is known as encino macho (Spanish) or tlacuauak tlakatl (Nahuatl), both of which translate as “male oak”. In traditional medicine, the bark is used to treat loose teeth or strengthen the gums: the bark is chewed till the mouth feels numb, or the bark is boiled and the liquid used as mouthwash. The sap is used in dyeing to make colours adhere better (Biblioteca Digital de La Medicina Tradicional Mexicana 2009). The catkins were used by the Otomi indigenous people as part of their diet. The wood is used as firewood and to make charcoal; it is also recommended for use in furniture making (Romero Rangel et al. 2015).