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The Status of Quercus oblongata

As part of our work for Trees and Shrubs Online it has been necessary to look into the correct application of certain names. One of these is Quercus oblongata D. Don, which in several databases and publications has been used to refer to the Himalayan oak known as Q. leucotrichophora A. Camus (originally Q. incana Roxb.), though it is not clear why. It is more likely to be a synonym of Q. lanata Sm. In the IOS’s Oak Name Checklist, Piers Trehane noted it as status dubium (dubious status) and suggested that it should be proposed for rejection.

Quercus oblongata was first published in Prodromus florae Nepalensis (A Preliminary Flora of Nepal) in 1825 by David Don (1799-1841), a botanist employed by Aylmer Bourke Lambert to curate his extensive herbarium. The Prodromus includes descriptions of specimens sent to Lambert from India by Francis Buchanan-Hamilton and Nathaniel Wallich. Don’s description is brief, mentioning only the shape of the leaf (oblong, pointed, base heart-shaped), its margin (spiny-toothed), its upper surface (glabrous), and its lower surface (yellow-felted).

Q. oblongata description

The last line of the description states that it was collected in what is currently known as Srinagar in Uttarakhand, India, by Kamrup (modern spelling), a collector who provided specimens for Wallich. In the same publication, Don described Q. lanuginosa, based on a specimen that has subsequently been determined to be Q. lanata.

In Arboretum et Fruticetum Britannicum, published in 1844, three years after Don had died, Loudon stated that “Professor Don, in his Prodromus Flora Nepalensis, had described Q. lanuginosa and Q. oblongata as two species; but he has since informed us that the specimen which he had of Q. oblongata being very imperfect he is now disposed to refer it to Q. lanata.

In order to clarify the situation, one would normally examine the type specimen on which Don based his description of Q. oblongata. However, this appears to be lost. Lambert’s herbarium fell into disarray towards the end of his life. Following his death, it was sold at auction and the herbarium, separated into lots, was dispersed to different herbaria around the world. As the specimen of Q. oblongata was provided by one of Wallich’s collectors, one would expect to find the specimen in the Wallich Herbarium at Kew, or in the herbarium of the Natural History Museum at the British Museum. However, searches there and in other herbaria have been fruitless. Hence, it is not possible to determine whether the specimen Don described, which he classified as “very imperfect,” is the same as Q. lanata or some other accepted name, or is truly a distinct species. To resolve this in favor of the first option, one would need to select a new type for Q. oblongata that matches Don’s description and could be shown to be the same as Q. lanata. Such a neotype would have to be collected from the same locality as the original specimen.

Quercus leucotrichophora leaves
Quercus leucotrichophora leaves on a tree at Iturraran Botanical Garden, showing the striking white undersides © Francisco Garin

Quercus lanata and Q. leucotrichophora are similar species, but they appear to differ in the color and thickness of the tomentum on the leaf undersides, as well as in leaf shape. This was shown in Gaurav Verma’s 2020 publication on the IOS website: “Destined to Encounter Quercus lanata (he used the name Q. oblongata in place of Q. leucotrichophora).

Q. leucotrichophora vs Q. lanata
Leaves of Quercus lanata collected in Kilbury Forest, Uttarakhand, India © Gaurav Verma

Quercus leucotrichophora leaves tend to be narrower, with undersides covered in whitish pubescence, while Q. lanata’s broader leaves have woollier, fawn-colored or russet abaxial surfaces.

Although Smith’s original description of Q. lanata (1814) referred to the undersides as “white”, the holotype and other specimens determined to be of this species show thick, yellowish tomentum.

Holotype of Quercus lanata
Holotype of Quercus lanata (BM000521982) © The Trustees of the Natural History Museum, London

The species with whiter tomentum was first described by Roxburgh in 1832 as Q. incana, a name considered illegitimate because it had been used earlier by Bartram to describe an American oak. In 1935, Aimée Camus introduced the name Q. leucotrichophora to replace Roxburgh’s illegitimate one.

Holotype of Quercus leucotrichophora
Holotype of Quercus leucotrichophora (BM001217646) © The Trustees of the Natural History Museum, London

We have not been able to find an original document that makes the decision that Q. oblongata is the correct name for Q. leucotrichophora. Don’s scant description, which describes the undersides as yellowish, suggests it is more likely to be Q. lanata than Q. leucotrichophora (the name of the latter, derived from Ancient Greek, means “bearer of white hairs"; Roxburgh’s epithet, incana, also means grey/white, in reference to the abaxial surface of the leaves).

The specimen that Don described as Q. lanuginosa (later determined to be Q. lanata) can be found in the Kew Herbarium.

Type of Quercus lanuginosa D. Don (now Q. lanata)
Type of Quercus lanuginosa D. Don, now Q. lanata (K000832212) © The Trustees of the Royal Botanic Gardens, Kew

If we accept Loudon’s account that Don was disposed to refer the specimen he had described as Q. oblongata to the species he had described as Q. lanuginosa, it seems reasonable to regard Q. oblongata as a synonym of Q. lanata, not of Q. leucotrichophora.

We hope this will encourage the use of the best-known name for this species, Q. leucotrichophora, which can be found listed as Q. oblongata or Q. lanata. The latter, as far as we know, is only represented in gardens by a single plant, at Wakehurst Place, West Sussex, Englan, introduced from Nepal as Q. lanuginosa, a name that has its own problems.

Acknowledgments

We'd like to thank Henry Noltie and Mark Watson of Royal Botanic Garden Edinburgh and Jacek Wajer and Norbert Holstein of the National History Museum for help in researching this article.