Quercus robur

Quercus robur, called the pedunculate oak, European oak, or English oak, is a flowering tree in the Fagaceae family, which includes beeches and oaks. This large tree is native to Europe and western Asia and is commonly planted in other temperate regions. It thrives on soils with near-neutral acidity in lowland areas and is ecologically important, hosting many herbivorous insects, acorn-eating mammals and birds, and fungi.

The name "pedunculate oak" comes from its acorns, which grow on a stalk called a peduncle. English oaks can reach very old ages, often living over 500 years, and some specimens are thought to be more than 1,000 years old. Their bark is thick and deeply fissured.

This deciduous tree usually matures at about 20 meters tall, sometimes reaching 40 meters, with a stout trunk typically up to 4 meters in girth (circumference at breast height), though some exceed 10 meters, and pollarded specimens have reportedly reached 14 meters. Older trees are often pollarded, with a main trunk (bole) about 3 meters long, and they tend to live longer and grow stouter than unpollarded ones. The crown is spreading and unevenly domed, with massive lower branches. The bark is greyish-brown, with shallow fissures and flat-topped ridges. Large burrs on the trunk often produce many small shoots. Oaks do not produce suckers but recover well from pruning or lightning damage. Twigs are hairless, and buds are rounded, brownish, and pointed.

Leaves are arranged alternately, broadly oblong or ovate, 6–14 cm long and 4–8 cm wide, with a short petiole (2–3 mm). They have a cordate (auricled) base and 3–6 rounded lobes that do not cut more than halfway to the midrib. The leaves are usually hairless or have just a few simple hairs underneath, dark green above and paler below, and often develop small disks of spangle gall by autumn.

Flowering occurs in spring (early May in Northern Europe), and the flowers are wind-pollinated. Male flowers appear in narrow catkins 2–4 cm long, arranged in small bunches. Female flowers are small, brown with dark red stigmas, about 2 mm across, and grow at the tips of new shoots on peduncles 2–5 cm long. The acorns are borne in clusters of 2–3 on a long stalk 4–8 cm long. Each acorn is 1.5–4 cm long, ovoid with a pointed tip, starting whitish-green and turning brown, then black. They sit in a distinctive shallow cup, useful for identification.