Turkey Oak

Quercus cerris

Turkey Oak Quercus cerris

A fast growing deciduos tree, this oak grows up to 30m (98ft) tall, and is a widely spreading specimen with long main branches rising from a relatively stout trunk. The bark is grey with fine, deep vertical fissures. The leaves are usually long and narrow, but sometimes long and ovate. The lobes are more pointed than Pedunculate Oak (Quercus robur), and they are a darker green and shiny, but paler and woolly on the underside. The stalks are hairy and are about 2cm long. In the autumn the leaves turn a rich orange brown. The male flowers are pendulous catkins of crimson flowers. The acorns have no stalks, and they are long, the cups deep and mossy covered in narrow, greyish scales. The acorns ripen in the second year.

Turkey Oak Quercus cerris leaves

Mainly grown in parks and gardens, or alongside roads, but it is also found naturalised in woodland. It is fairly tolerant of different soil types, and is also quite resistant to atmospheric pollution. A native of southern Europe, the Turkey Oak was introduced and raised by J Luccomb, an Exeter nurseryman, in 1735. Today it is fairly common and widespread.

Turkey Oak Quercus cerris leaf

Turkey Oak Quercus cerris acorn

Turkey Oak (Quercus cerris), Bournemouth park, Dorset and Warley Woods, Staffordshire, England. August and September 2013.

Knopper Gall

Andricus quercuscalicis

Whilst on a walk through a local churchyard I noticed these fine old Turkey Oaks (Quercus cerris) in the grounds. I saw all these strange knobby growths on the acorns. I took these series of photographs, and although I knew they were a plant gall of some kind, I later identified them as the Knopper Gall, which is caused by a tiny wasp. The asexual generation of Andricus quercuscalicis develops on the acorns causing the formation of the galls. Green and sticky to begin with, the galls eventually flush red and then turn brown and woody.

The galls fall from the trees in late summer, and the adult gall wasps will emerge the following spring, although some may remain within the galls for up to four years. Eggs are then laid in Turkey Oak buds which result in tiny cone-shaped galls on the male catkins. The Knopper Gall arrived in Britain in the 1960s, and it did cause some alarm at first. It can be extremely abundant in some years (the trees I saw were completely covered) but there are usually enough acorns left for the trees to survive.

Photographs taken August 2013, local churchyard, Staffordshire.