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.
Quercus pubescens Willd.
Quercus pubescens Willd. is a species with a wide native range, found across the European continent, from Portugal to Lebanon and from Russia into Southern Germany. This oak takes its name from the Latin epithet pubescens, meaning covered with soft short hairs, due to the hair growth that characterizes this species. However, these hairs, which represent the primary identifying feature of this oak, may vary from one population to another and depend on the state of the growth cycle at which stems and leaves are observed. The hairs that give the whitish appearance in the spring gave rise to the French local name chêne blanc.
|Q. pubescens, St. Sardos, near Aboretum de la Bergerette. (Photo: Guy Sternberg)|
Quercus pubescens is a species of the plains and mountains up to 1,400 m altitude in France (1,700 m in southern and eastern Europe) and is not very demanding in terms of pH and soil structure. It occurs on shales, marls, sands, silts, and calcareous sites. However, it is clear that when grown in deep alluvial soils it can reach more than respectable dimensions.
In the National Forest of Bercé (Sarthe) during the IOS Pre-Conference Tour, specimens of about 50 m in height were observed by participants. This species does not like saturated soils and shows good tolerance to low humidity and dry summer conditions, as is evidenced by its growth in the Causses of the Massif Central in France.
Its wood is pale yellow and its sapwood not always clearly visible. The trunk is often crooked and it is rarely used except as firewood, sleepers on railway tracks or to provide coal. Among its many cultural uses, its acorns are used (historically and currently) for livestock fodder, including pigs in Italy, and it is a favored species for the production of truffles.
This oak is generally divided into two subspecies: Q. pubescens Willd. subsp. pubescens and Q. pubescens subsp.crispata (Steven) Greuter & Burde, but others have been described. This species has been known by the synonyms Q.lanuginosa Thuill. and Q.virgiliana Ten. There are three well-known cultivars of Q. pubescens (‘Miggaziana’, ‘Aydin’ and ‘Dissecta’) and many known hybrids which can be found on oaknames.org. In Lebanon, hybrids with Q.cerris produce Q. ×kotschyana O. Schwarz (although this could be a cross with its oriental form Q.pubescens subsp. crispata). Elsewhere, it can hybridize with a complex of species including any European white oak and it is frequent to find hybrids in the north of its range with Q.petraea (Matt.) Liebl. and Q.robur L.
|Le chêne de Murs, Vaucluse, France (Photo Jean-Luc Mettey).|
How to correctly identify Quercus pubescens and separate it from Q.petraea
Observation should take place in spring during the first weeks after bud break and again in fall during fruiting. In spring, the newly formed buds and leaves of Q. pubescens are tomentose, white or pinkish-white in color. Q. petraea has leaves and buds that are hairless (or with very discreet hairs on midrib), glabrous and yellowish-green or reddish.
At the end of the growing season, we can also observe the same morphological characteristics as in spring, but be careful as oaks are usually polycyclic and if leaves sprout in the second half of summer, it is like observing a spring shoot again. In fall, Q. petraea will have glabrous leaves and stems. With Q. pubescens, the stems will have certainly lost much of their pubescence but are usually always at least a little bit hairy. However, it can happen that these shoots are glabrous, in which case the leaves must be observed. Q. pubescens may be smooth, or nearly so on the adaxial face, but the abaxial face is always hairy although the hairs may not persist on the veins and the base of the main rib. The presence of hairs on twigs in winter as well as marcescent leaves also helps identify pubescent oak. Bear in mind that as we move further north in the range, the quantity of hairs decrease at the end of the growing season!