Pedunculate oak  (Quercus robur)

The pedunculate oak is classified as Least Concern (LC) on the IUCN Red List (1), and is widespread and common (3).

The pedunculate oak (Quercus robur), the 'king of trees' has a special place in the English psyche, and is a well-loved symbol of strength and duration (4). It is a magnificent tree, with a broad, irregular crown. The bark is grey and fissured, and develops burrs as it ages (5). The massive main branches often develop low on the trunk and become twisted and gnarled with age (2). The leaves have five to seven pairs of lobes, forming a typical 'wavy-edged' outline; the upper surface is dark green, the underside is paler, and young leaves are often covered in a layer of fine downy hairs (2). The fruits, known as acorns, occur in clusters on long stalks known as peduncles (hence the common name of this species); the egg-shaped acorns sit in scaly cups that measure up to 18 millimetres across (6).

The pedunculate oak is widespread throughout Britain and much of the rest of Europe, with the exception of the far north and some areas of the Mediterranean (2).

You can view distribution information for this species at the National Biodiversity Network Gateway.

The dominant tree of deciduous woods in Britain, the pedunculate oak occurs in coppice woodland, high forest and ancient wood pastureland, and has often been planted in hedgerows. It is able to grow in a range of soil types, but prefers those that are fertile and heavy (3).

The pedunculate oak flowers between May and June. Towards the end of summer the acorns begin to ripen, becoming fully ripe by October (2). The acorns are rich in starch and tannins, and are eaten by small mammals and a number of birds. Jays and squirrels are extremely important in dispersing acorns away from the parent trees; they bury them for later consumption, and many of these acorns germinate (4).

Young oak trees are vulnerable to insect predation. They grow very quickly, but after reaching 100 to 200 years of age their rate of growth slows down. After this time, however they continue to increase in girth (5). The pedunculate oak is a very long-lived species; specimens typically live for up to 500 years, but some oaks are known to be 700 to 1200 years old (5). Indeed, Britain has more ancient oaks than any other country in western Europe (4).

Acorns were once widely used to feed pigs; they were also ground down to make a substitute for coffee and even a type of bread (5). A good crop of acorns was used to predict a good harvest, and a heavy fall of acorns was thought to signal an impending harsh winter (5). Oak Apple Day occurs on the 29th of May, and commemorates the return of Charles II to London after exile. During exile, he was hidden inside an oak tree, and he declared that the 29th of May should be set aside as a holiday for 'the dressing of trees'. It is not certain why the day is named after oak apples, the spongy galls caused by parasitic wasps (4).

Upland oak woodlands have declined by 30 to 40 percent over the last 60 years as a result of re-planting with conifers, conversion to grazing land, overgrazing by sheep and deer, and unsuitable management (7). The decline in the ancient technique of coppicing has resulted in oak woodlands becoming more shaded; acorns do not germinate as well in these conditions. Many oak forests have a skewed age structure, as young trees are not able to regenerate (4). This may cause problems for many of the rare species that are dependent on ancient oaks; as the old trees die there will not be trees in the vicinity of a suitable age, so entire communities are at risk (8).

Upland oak woodland is a priority habitat under the UK Biodiversity Action Plan (UK BAP). An action plan has been produced to guide the conservation of this habitat (7). Not only is the pedunculate oak of important cultural significance, it is a beautiful, majestic species. Furthermore, the communities of plants, animals and fungi that are associated with oak trees are often unique, and internationally significant. Conserving this 'king of trees' is therefore of utmost importance (7).

There may be further information about this species available via the National Biodiversity Network Gateway.

For more on British trees:

• The Tree Council:
  http://www.treecouncil.org.uk
• British Trees:
  http://www.british-trees.com

The UK BAP Habitat Action Plan for upland oakwood:
http://www.ukbap.org.uk