Pedunculate Oak - Quercus robur

Also known as English Oak, or sometimes the Common Oak, this is our largest and most common native deciduous trees that grows up to 40m in height and has been known to live over 1000 years! The clustered acorns and the deeply rounded lobed leaves make the Pedunculate Oak unmistakable.

Habitat

It is a dominant tree of deciduous woods in Britain and grows in coppiced woodlands, ancient woodlands and wood pastureland, and has often been planted in hedgerows. It grows in a range of soil types, but prefers those that are fertile and heavy.

Description

The leaves are the easiest way to identify the oak – They are long and oblong shaped, pinnate-lobed and deeply lobed and have little to no stalk; they also often have fine soft hairs and the underside is usually paler than the upper surface.

Other distinguishing features that make up these magnificent trees are the broad irregular crown and its bark. In younger trees the bark is just slightly fissured, but these deepen as the trees get older and develop burrs. The tangled branches become twisted and gnarled with age.

Flowers are out April to May before the leaves are fully open and look like golden-green catkins. The acorns (the fruit) are out September to October. The acorns are in individual rough cups with up to three together on a long stalk. The Pedunclulate oak’s acorns are described as pedunclate as they grow on these long stalks known as peduncles.

Biology

The shape of the tree is determined by the openness of the location and the prevailing weather patterns. If deer browse the lower branches there will be a flat base to the tree. An oak growing in the open can increase its girth by about 2.5cm per year.

Initially they grow very quickly until c.100 years when the growth slows down whilst their girth continues to increase, there are few changes to the shape of the tree during this time and this can last for up to 300 years. This can be followed by up to another 300 years as the tree slowly declines and hollows until it dies. Although they can live to over 1000 years old they usually live up to 600 years and Britain has the highest number of ancient oak trees in Europe.

By midsummer the leaf canopy will be at it’s fullest. Come autumn the leaves start to turn colour into red and orange hues. Being a deciduous tree it loses its leaves at the end of autumn. The acorns that fall at this time are a food source for many birds and mammals, and are especially highly prized by Jays and Grey Squirrels. The flowers provide food for the Dormouse and numerous insects live on the leaves, buds, and in the acorns.

Oaks also bear numerous fruit-like growths called galls. These are caused by gall wasps, of which there are 30 species in Britain that affect oak trees, each one lays its eggs in a particular part of the tree – roots, bud, bark, leaves, catkins or acorns. The small larvae secrete chemicals that cause the oak trees to produce tissues that enclose them. They feed on the layer of cells within the galls before they pupate and turn in adult wasps and then emerge. They do not cause any damage to the tree.

Threats

Oak woodlands have undergone a high rate of decline due to replanting with conifers, clearance for farmland and the decline of coppicing. Coppicing is an ancient technique of management, without it oak woodlands become more shaded and acorns do not germinate well in dark conditions. This results in a ‘top heavy’ age structure with no young trees, this creates many problems for rare species dependant on ancient oaks as once the old trees have died there are none in the vicinity of a suitable age.