Pedunculate oak (Quercus robur)

Also known as: common oak, English oak, European oak
Synonyms: Quercus longaeva
  
French: Chêne Pédonculé
KingdomPlantae
PhylumAnthophyta
ClassMagnoliopsida
OrderFagales
FamilyFagaceae
GenusQuercus (1)
SizeHeight: up to 45 m (2)
Top facts

The pedunculate oak is classified as Least Concern (LC) on the IUCN Red List, with the subspecies Quercus robur ssp. imeretina being listed as Vulnerable (VU) (1).

The pedunculate oak (Quercus robur), the 'king of trees', has a special place in culture and folklore, and is a much-loved symbol of strength and duration (3) (4). It is a magnificent tree, with a broad, irregular crown. The bark of the pedunculate oak is grey and fissured, and develops burrs as it ages (5) (6). The massive main branches often develop low on the trunk, more so than in other oaks, and become twisted and gnarled with age (2).

The leaves of the pedunculate oak have four to seven pairs of lobes, forming a typical 'wavy-edged' outline. The upper surface of the leaf is dark green, the underside is paler, and young leaves are often covered in a layer of fine downy hairs (2) (6). The leaves of the pedunculate oak are easily distinguished from those of other oaks by the presence of two small lobes just where the leaf joins the stalk (7).

The male flowers of the pedunculate oak occur on slender ‘catkins’ measuring two to four centimetres in length, while the female flowers are brown and spherical and grow in small groups at the end of ends of the branches (6). The fruits of the pedunculate oak, known as acorns, occur in clusters on long stalks known as peduncles, which give this species its common name (4) (8). The egg-shaped acorns are whitish-green, later becoming dark brown, and sit in scaly cups that measure up to 18 millimetres across (6) (8).

The pedunculate oak is widespread throughout the United Kingdom and much of the rest of Europe, with the exception of the far north and some areas of the Mediterranean (2). It also occurs in Russia and parts of Asia Minor, central Asia and North Africa (1) (4) (6).

Over the last century the pedunculate oak has been planted extensively worldwide, especially in the New World. A hybrid between this species and Quercus canariensis was planted in Australia to shade homes and schools, and these specimens have now become naturalised (7).

The dominant tree of many deciduous woodlands, the pedunculate oak occurs in coppiced and pollarded woodland, parks, gardens, high forest and ancient wood pastureland, and has often been planted in hedgerows (6) (9). It is able to grow in a range of soil types, but prefers those that are fertile and heavy (9). Unlike some other trees within the same family, the pedunculate oak can also thrive in heavy clay soils (7).

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 and relied upon by many small mammals and a number of birds. Jays and squirrels are extremely important in dispersing acorns away from the parent trees, as they bury them for later consumption and many of these acorns germinate (3) (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, typically living for up to 500 years, although some oaks are known to be 700 to 1,200 years old (5). The United Kingdom has more ancient oaks than any other country in Western Europe (3).

Acorns were once widely used to feed pigs, and were also ground down to make a substitute for coffee and even a type of bread (5). The acorns of the pedunculate oak are lower in tannins than most, making them more palatable to humans (7). 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 in England 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 (3).

The scientific name of the pedunculate oak, robur, comes from the Latin for ‘strength’, and refers to this tree’s robust, sturdy nature. The pedunculate oak has long been used for its strong, durable timber and was a mainstay material for construction, boatbuilding and barrels, while its bark has been used in leather tanning (4) (7).

The pedunculate oak is a widespread species and is not currently considered to be at risk of extinction. However, one subspecies, Q. r. ssp. imeretina, occurs only in a small part of western Georgia and Russia, and is under threat from felling and the spread of agriculture (1).

In the United Kingdom, oak woodlands have declined greatly in the last few centuries (4), and upland oak woodlands have declined by 30 to 40 percent in over the last 60 years or so. The main causes of this decline include re-planting with conifers, conversion to grazing land, overgrazing by sheep and deer, and unsuitable management (10). The decline in the ancient technique of coppicing has resulted in oak woodlands becoming more shaded, and acorns do not germinate as well in these conditions (3). Many oak forests also have a skewed age structure, as young trees are not able to regenerate (3).

The pedunculate oak may also be under threat in the United Kingdom from a fungal disease known as ‘sudden oak death’. Although native oaks currently appear to be relatively resistant to this disease, it may potentially pose an increased threat in future, especially if oak trees become stressed by the effects of climate change (4). A condition known as ‘acute oak decline’ has also recently been identified in the United Kingdom, and is known to kill native oaks. However, its causes have yet to be fully understood (4) (11).

Upland oak woodland was previously a priority habitat under the UK Biodiversity Action Plan (UK BAP). An action plan was produced to guide the conservation of this habitat, and this plan aimed to maintain current upland oak woodland and improve its condition, as well as to expand it (10). The UK BAP was succeeded by the ‘UK Post-2010 Biodiversity Framework’, which sets out priorities for protecting the United Kingdom’s biodiversity (12).

Not only is the pedunculate oak of important cultural significance, but it is also a beautiful, majestic species. Furthermore, the pedunculate oak supports a wide range of other plants, animals and fungi (4), so conserving this ‘king of trees’ is therefore of utmost importance for many other species.

Find out more about the pedunculate oak and oak woodland:

More information on UK tree conservation:

Authenticated (14/03/13) by Richard Browne.

  1. IUCN Red List (February, 2013)
    http://www.iucnredlist.org/
  2. Humphries, C.J., Press, J.R. and Sutton, D.A. (2000) Hamlyn Guide to Trees of Britain and Europe. Hamlyn, London.
  3. Mabey, R. (1996) Flora Britannica. Sinclair-Stevenson, London.
  4. Royal Botanic Gardens, Kew - Quercus robur (February, 2013)
    http://www.kew.org/plants-fungi/Quercus-robur.htm
  5. Godet, J. (1986) Collins Photographic Guide to the Trees of Britain and Northern Europe: A Guide to Identification by Leaves and Needles. William Collins Sons & Co. Ltd, London.
  6. Mitchell, A. (1978) Collins Field Guide: Trees of Britain and Europe. HarperCollins Publishers, London.
  7. Browne, R. (March, 2013) Pers. comm.
  8. Press, B. (1996) Collins Wild Guide: Trees. HarperCollins Publishers, London.
  9. Preston, C.D., Pearman, D.A. and Dines, T.D. (2002) The New Atlas of the British and Irish Flora. Oxford University Press, Oxford.
  10. UK Biodiversity Action Plan: Habitat Action Plan - Upland oakwood (March, 2003)
    http://jncc.defra.gov.uk/page-5718
  11. Forestry Commission - Acute oak decline (February, 2013)
    http://www.forestry.gov.uk/fr/INFD-7UL9NQ
  12. JNCC - The UK Biodiversity Action Plan (UK BAP) (February, 2013)
    http://jncc.defra.gov.uk/page-5155