By John Hughes

The Turkey oak Quercus cerris originates, as might be expected, in Turkey and other areas of south-central and south-east Europe, reaching into south-west Asia. It has been cultivated in Britain since the early 18th century, and has been found in the wild since 1905. Its rapid northward spread in the last 50 years is yet further evidence of global warming: naturalised examples have now been recorded in the Great Glen. It is a common tree in Dulwich, with some very fine examples to be seen. Perhaps the finest is the one in Dulwich Park with an accompanying plaque deservedly identifying it as one of the Great Trees of London, the only one in Dulwich.

The trunk of Turkey oak tends to be much straighter than either of our two native oaks, English oak Q. robur and Sessile oak Q. petraea. Tree books often draw attention to the orange colour seen in the furrows of the bark of a Turkey oak. This can be hard to spot, though some orange colouring is visible at the back of the Dulwich Park tree and on the undersides of its lower branches. The leaves of a Turkey oak are darker than those of our native trees, so that it can look from a distance like a tall Holm oak. The leaves are very variable in shape and size, though they have an overall tendency to be narrow, almost ribbon-like. They have minute grey-felted hairs beneath. What gives a tree away as a Turkey oak is that its buds have persistent, long, twisted whisker-like stipules, occasionally obscuring the bud. These are most clearly visible in winter. The acorns of Turkey oak are stalkless, like those of Q. petraea. The scales of its acorn-cup are densely covered with whiskery hairs, giving it a somewhat shaggy appearance.

Some Turkey oaks have much more regular leaves than others and, if looking at one of these, it is worth considering whether you might have a Chestnut-leaved oak Q. castaneifolia before you. This is a much rarer tree. Its buds have the same whiskery stipules as Turkey oak and its acorn-cups also have a shaggy look. But its leaves have small regular triangular lobes, with a minute bristle to the vein tips (scarcely seen in Turkey oak). Dulwich is lucky to have a fine full-grown Chestnut-leaved oak on College Road, at the junction with Frank Dixon Way.

Dulwich also has two interesting hybrids between Turkey oak and Cork oak Q. suber. Accordingly, they both have the same scientific designation: Q. × hispanica. The first, Lucombe oak, grows by the Gallery Road entrance to Lovers Walk. It is named after William j++6Lucombe, an Exeter nurseryman who raised it in 1762. The second, Fulham oak, is so called because it was grown by Whitley and Osborne of Fulham in 1783. It grows in the Picture Gallery garden (location given on the new tree map by the College Road entrance). It is supposed to have a corkier bark than Lucombe oak, but the Picture Gallery tree does not yet display this, unlike the specimens to be seen in the gardens of Fulham Palace, for example. It is still a young tree, however, and so may well display more of its Cork oak parentage as it ages.