Quercus variabilis Blume

This tree, of wide distribution in eastern and southern China, is of significant economic and ornamental importance. Though not on a par with that of Q. suber, either in quality or thickness, its cork is used industrially in roofs and floats. The wood is valued for boat building and general construction purposes; the acorn cups produce a black dye used to color silk. Cloud ear fungus (Auricularia polytricha) is grown on its felled logs in western Hubei (Sargent 1917); its logs are also well-suited for the cultivation of shiitake mushrooms (Lee et al. 2014). In China and Japan it is often planted next to pagodas or temples, thus acquiring sacred connotations. Le Hardÿ de Beaulieu & Lamant (2010) enthuse about the ornamental value of this oak, its elegant habit, and particular interest in every season. A particularly beautiful feature is the band of dark pigment between the veins of expanding leaves in spring, giving the leaf a striking bicolor effect for a few days.

It is similar to Q. acutissima, from which it can be distinguished by the whitish undersurface and smaller teeth of the leaves, and the corkiness of the bark in adult specimens. For Bean (1976), Q. variabilis is ‘a finer tree’ than Q. acutissima. Shaun Haddock notes that the two species seem to germinate to the beat of different drummers: Q. variabilis acorns sprout immediately on falling from the tree, Q. acutissima awaits spring, a delay that allows it to establish in colder climates and maintain a wider range in Japan (Haddock 2008; Hiroki & Kamiya1 2005).

Chinese Cork Oak was introduced to the UK by Robert Fortune in 1861, from hills west of Beijing where it is a common tree. He sent large quantities of acorns which germinated successfully and grew ‘luxuriantly’ in Standish’s nursery at Ascot; however, none of these trees appear to have survived (Elwes & Henry 1906–1913). Emil Bretschneider later sent acorns, also from the mountains around Beijing, to the Arnold Arboretum in 1881. In 1890, Sargent reported that it was perfectly hardy there and growing rapidly, the leaves turning bright canary yellow in November (Bretschneider 1898). Bretschneider also sent seed from the same source to Kew in 1882, where it also flourished but did not survive for long. A tree that has survived at Kew was sourced from the Arnold Arboretum and planted in 1909; it measured 17 m × 53 cm dbh in 2010. The girth champion for the UK and Ireland grows at Tortworth Court Hotel, planted in 1881, and measured 17 m × 68 cm dbh in 2015. Two trees are joint height champions according to the Tree Register: one at Hollycombe, West Sussex, 21 m × 65 cm in 2018, up from 19 m × 49 cm in 1984, the other at Borde Hill, Sussex, 21 m × 65 cm in 2015, up from 20 m × 44 cm in 1983 and 10 m × 29 cm in 1967 (Tree Register 2021; Clarke 1988; Bean 1976). At Arboretum du Passadou, France, a tree was estimated at about 25 m tall in 2019 (pers. obs.)

Quercus variabilis is cultivated in botanic gardens and arboreta in all four hemispheres. At Mereweather Arboretum in Victoria, Australia, a specimen from seed collected in southern Yunnan is semi-evegreen (Funk 2015); at Eastwoodhill Arboretum in New Zealand it has grown well: a tree sourced from Hillier Nurseries reached 21 m tall by 2017 and a study of Chinese species growing there suggested that Chinese Cork Oak could be more widely grown in New Zealand. (He & Luo 1992). Trees grown from seed from the Eastwoodhill tree are growing in Grigadale Arboretum in Argentina (Grigadale Arboretum 2021); also in Argentina, the San Miguel Arobretum has several trees from seed sourced in Japan (P. Laharrague, pers. comm.). The species is found in many gardens in the US, including from recent introductions of wild collected seed, e.g. a NACPEC 2002 collection from Shaanxi, the source of trees at The Morton Arboretum, Chicago Botanic Garden, and Morris Arboretum (Quercus Multisite 2021). At Washington Park Arboretum it was 26.2 m × 49 cm in 2004 (R. Larson pers. comm.2020). At UBC Botanical Garden in Vancouver, Canada, a tree from seed sourced in South Korea and accessioned in 1986 is about 20 m tall (D. Justice pers. comm. 2021).

According to J.R.P. Van Hoey Smith (1992), the species’ hardiness in Trompenburg Arboretum in the Netherlands depended on the origin of the seed: seedlings grown from acorns sourced from Eastwoodhill Arboretum froze down to the ground every year, whereas high-altitude acorns from Mount Emei in Sichuan, China fared much better.

The species hybridizes with Q. acutissima in the wild in zones where the two species overlap (Hiroki & Kamiya1 2005); there is a herbarium specimen at Sir Harold Hillier Gardens of this taxon, wild-collected in Korea (Royal Botanic Garden Edinburgh 1997). Several putative hybrids between Q. variabilis and some section Quercus oaks (Q. garryana, Q. turbinella, Q. macrocarpa) emerged from experiments carried out by Walter Cottam at the University of Utah in the 1960s. These crosses are questionable and do not display any Q. variabilis characters. The authors of the experiment pointed out that while their analyses confirmed that the plants were hybrids, they could not confirm that the pollen parent was Q. variabilis. It is worth noting that attempts to create crosses between section Quercus pollen with Q. variabils as female parent all failed (Cottam et al. 1982).

The epithet means ‘variable’. Presumably Blume chose it to express his frustration in trying to pin down the shape of the leaves: he describes their base as obtuse or subcordate, the leaf blade as oblong or sometimes wider above or slightly fiddle-shaped, the apex as acute or obtuse, the margin as wavy or serrate or serrulate… The leaves are in fact no more variable than those of other oaks and much less variable than some; he may have been presented with exceptionally irregular herbarium samples. The common name in Japanese, abemaki, derives from abata (‘pockmark scar’, shortened to abe in the Okayama dialect) in reference to the appearance of the trunk, and maki, which may mean ‘useful tree’, or ‘firewood’, or may be a local name for Q. serrata in Okayama prefecture (K. Tokunaga pers. comm.). The hybrid of Q. variabilis and Q. acutissima is known as abekunugi (Botanica 2021).