A deciduous tree attaining the same size as the common oak, Q. robur, and not differing in its bark; it differs in its habit, having straighter branches and a trunk that usually penetrates further into the crown than is the case with the common oak; buds usually rather more elongated and acute at the apex. Leaves broadest at or only slightly above the middle, hence not so markedly obovate or oblanceolate as in Q. robur and less tapered to the base, which is cuneate or cordate and lacks the auricles characteristic of the common oak; the texture is usually somewhat firmer, the upper surface rather more glossy, and the underside has persistent hairs on the midrib and main veins and sometimes scattered stellate hairs on the surface of the blade; intercalary veins, i.e., veins running out to the sinuses between the lobes, are much less frequent than in Q. robur, and the lobing is more regular; the stalk, very short in the common oak, is 3⁄8 to 11⁄4 in. long in the durmast oak. Female flowers with almost sessile stigmas (styles usually well developed in Q. robur). The common name ‘sessile oak’ refers to the fruits, which are borne directly on the twig and not on a long slender peduncle as in Q. robur. The scales of the acorn-cup are rather more numerous and more closely imbricated than in Q. robur.
The general distribution of Q. petraea is similar to that of Q. robur, with the notable difference that it does not extend so far to the east on the Continent. In the British Isles the durmast oak avoids the heavy clay soils of the Weald and the Midland Plain but is the commoner species on siliceous soils in the north and west, and is also to be found on light, non-calcareous soils in southern England, often in association with the common oak.
The fine tree at Whitfield, Herefordshire, mentioned in previous editions, still exists and measures 135 × 141⁄4 ft (1963). Others measured recently are: Oakley Park, Shrops., 111 × 221⁄4 ft and 85 × 231⁄4 ft (1971); Nettlecombe, Som., 112 × 213⁄4 ft and 95 × 23 ft (1959); Shobdon, Heref., about 90 × 30 ft (1973); Croft Castle, Heref., 50 × 261⁄2 ft (1960); Knole Park, Kent, 130 × 171⁄2 ft (1969).
On the Continent, the durmast oak comes into leaf and flowers up to two weeks later than the common oak and hybrids between them are therefore by no means common. It is said, however, that in the British Isles there is less difference in flowering time and that hybrids are commoner in consequence. However, both species are variable and minor deviations from the norm are sometimes wrongly taken to be the result of hybridity. For example, the fruits in the durmast oak are sometimes borne on peduncles, but in such cases the peduncle is thick at the base, where it resembles a normal twig. True hybrids, for which the correct name is Q. × rosacea Bechstein, would show such combinations as auricled leaves, downy beneath, on stalks of intermediate length; or peduncu late acorns, leaves almost glabrous beneath but not auricu-late, etc.
The durmast oak has not been so prolific of varieties as Q. robur, but most of the following are or have been in cultivation at Kew:
cv. ‘Afghanistanensis’. – Leaves oval or obovate, with shallower lobes than the type. Fruits with a distinct stalk as much as 1⁄2 in. long. It was distributed by Booth’s Flottbeck Nurseries, Hamburg, around the middle of the last century. It is unlikely to have come from Afghanistan, as they claimed. There are three examples at Kew, the largest 85 × 73⁄4 ft (1971).
cv. ‘Cochleata’. – Leaves decurved at the margin, so that the centre is humped or hooded. The tree at Kew, planted in 1871, has mostly reverted.
cv. ‘Columna’. – Of columnar habit, with rather narrow and elongated, sparsely and irregularly lobed leaves. Put into commerce by Messrs Hesse of Weener, Hanover, shortly before the second world war.
cv. ‘Falkenbergensis’. – According to the original description this had short, serrated leaves resembling those of Q. cerris. They are very downy beneath. It was discovered near Falkenberg near Hamburg and was put into commerce by Booth’s Flottbeck Nurseries in 1837.
cv. ‘Giesleri’. – Leaves long and narrow, entire or unequally lobed. Put into commerce by Späath towards the end of the last century.
cv. ‘Insecata’. – Leaves very long and narrow, with irregular, slender, forward-pointing lobes, some leaves reduced almost to threads. Leaves on the Lammas growths more or less normal. It was originally named Q. sessiliflora laciniata, a name used much earlier by Lamarck and de Candolle for a wild form with deeply lobed leaves.
f. mespilifolia (Wallr.) Rehd. – Leaves lanceolate to narrowly oblong, up to 5 in. long, 1 in. wide, tapered at both ends, sinuately lobed to almost entire. It occurs occasionally in the wild, and was described by Wallroth, as Q. robur var. mespilifolia from a tree found in the Harzgebirge. The garden variety ‘Louettei’ is of this nature, but is of rather pendulous habit. In the very similar f. sublobata (Kit.) Schneid., the leaves are more lobed, but still unusually long and narrow. Here belongs the garden variety ‘Geltowiensis’, distributed by the Royal Nurseries at Geltow near Potsdam.
There are two specimens of f. mespilifolia at Kew, the larger, on Palace Lawn, measuring 72 × 7 ft (1970).
cv. ‘Muscaviensis’. – Leaves of first growth often nearly or quite entire, those of the second or July growth nearer the type and lobed.
cv. ‘Pendula’. – Branches very pendulous, forming an umbrella-shaped crown. Raised in France around 1867 in the garden of the Military Hospital, Vincennes, and propagated by grafting.
cv. ‘Rubicunda’. – Young leaves reddish purple. The same or a similar variety is known as ‘Purpurea’.
Q. dalechampii Ten. Q. lanuginosa subsp. dalechampii (Ten.) Camus; Q. robur subsp. sessiliflora var. tenorei A. DC. – A poorly defined species which has been very variously interpreted by botanists. It appears to be intermediate between Q. petraea and Q. pubescens, and is possibly the result of past hybridisation between them. According to Mme Camus it is confined to Italy (mainly the south). Dr Schwarz, who gives a description greatly at variance with hers, attributes to it a wider range.
Q. iberica Bieb. – Very closely allied to Q. petraea. Leaves with up to eight or even ten pairs of lobes, usually with rather large axillary tufts of hairs beneath. Fruits on a short peduncle. Native of Transcaucasia, said to be common around Batum.
Q. mas Thore – This is recognised as a distinct species by Dr Schwarz, but Mme Camus doubted whether it was really any more than a local variant possibly meriting the rank of subspecies. The leaves are rather larger than in Q. petraea, with up to ten pairs of narrowish, forward-pointing lobes; the fruit peduncles are silky hairy. Pyrenees and N. Spain.