Oaks

Pedunculate (English) oak
Quercus robur

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Pedunculate oak belongs to the genus Quercus and is a member of the Beech family (Fagaceae).

The pedunculate or English oak (Quercus robur) is a deciduous tree able to reach heights of 40m and flowering April to May.

Lifespan: oaks can reach considerable ages in excess of 1000 years, and when coppiced may live even longer.

 

Characteristics

Pedunculate oak is a large spreading tree, heavily branched with grey, deeply fissured bark. Twigs and buds are hairless. Leaves are alternate, oblong with four to five rounded side lobes; the lobes at the base of the leaf (auricles) are also rounded. Leaf stalks are short (up to 5mm).

Pedunculate oak is monoecious: both male and female flowers are found on the same tree. Male flowers are long, green pendulous catkins (up to 4cm). Female flowers appear at the tips of shoots and comprise a cluster of bracts surrounding a bud-like structure with three styles. Both appear with the leaves in spring. Seeds are acorns in a scaly,

Pedunculate oak tree

 

 

 

woody cup – one, two or three together on one long common stalk or ‘peduncle’. Oak is wind pollinated.

Spring leaves are often hastily eaten by insects hence a second flush is produced in summer traditionally termed ‘Lammas’ growth as it often coincided with the Lammas wheat harvest festival on 1 August.

Pedunculate oak leaves

Distribution

Pedunculate oak is native to the UK (except the north Scottish islands) and to most of Europe.

Pedunculate oak dominates woods and hedgerows mainly in the lowlands of south, east and central England on heavy, moderately acidic to alkaline soils. This lowland oak woodland is often characterised by carpets of bluebell, wood anemone or dogs mercury.

Pedunculate oak frequently hybridises with our other native oak; sessile oak (Quercus petraea) and their ranges overlap.

Both species are very similar; having similar human uses and wildlife value. They are often cited in woodland terms as though they were one species.For example, oak woodland (encompassing both pedunculate and sessile species) accounts for 23% of broadleaf woodland in the UK and oak (of either form) is our most common broadleaf tree.

Whether pedunculate or sessile our native oaks are cherished for their wildlife value; supporting more species in the UK than any other tree, and for their cultural heritage – many ancient and veteran specimens have graced our landscape for hundreds of years.

Human value

Pedunculate oak timber is attractive deep yellow-brown with lighter sapwood. It is known for its strength; the faster it is grown the stronger it is.

Pedunculate oak has been the traditional building material for timber-framed buildings since medieval times and the Royal Navy was founded on ships built from oak. The Latin name robur means ‘sturdy’. Oak bark was used in the leather tanning industry and acorns were used to fatten livestock for winter.

Today oak timber from both native species is used for furniture, high-class joinery, panelling and veneers. Because of its durability outdoors it is used for fencing, gates and boat building. It also makes very good firewood.

Pedunculate oak can be planted to improve the structure and drainage capacity of heavier soils. In general oak may benefit from climate change in terms of greater seed productivity but may suffer on sites prone to drought.

Pedunculate oak flowers
Veteran oak tree

Wildlife value

Both pedunculate and sessile oaks are without doubt our most important wildlife trees in the UK; they support many hundreds of species.

Among these are the larvae of several hundred moths including the festoon, frosted green, small brindled beauty and blotched emerald, as well as the rarer false mocha, heart moth, orange upper wing and dark crimson underwing. The purple hairstreak butterfly also relies upon oak for food.

The oak is a favoured foraging tree for many species such as blue tits, great tits, tree creepers, chaffinches, woodpeckers, wood mice and dormice and the acorns are enjoyed by jays, wood pigeons, squirrels and wild boar.

Long-lived or veteran oak trees provide a variety of decaying and dead wood habitats which support wood-boring insects such as stag, long horn, click and bark beetles. Cavities in the tree provide nesting space for tawny owls and bats such as the noctule, Bechstein’s, barbestelle and natterer’s.

Decaying oak also supports a wide range of fungi: the oak bolete, oak bracket, oakbug milk cap and oak mazegill to name a few and numerous lichen and moss species.

Pedunculate oak is an important component of wood pasture and parkland and of lowland mixed deciduous woodland; both of which have habitat action plans under the UK Biodiversity Action Plan.

Management

Pedunculate oak is a light-demanding pioneer species which is wind firm and cold hardy. Seedlings compete well with most grasses but may be frost tender. Although a late successional tree, it is not dependent upon shade to thrive.

Prefers moderate to rich fertile, heavy soils that are well drained to moist. It does best on more calcareous sites and can tolerate some waterlogging.

Acorns ripen September to November, and can be collected during this time and sown straight away or pre-treated to simulate cold conditions and sown in late March. Acorns are first produced once the tree has reached 40 to 50 years of age; the best crops occurring after 80 years.

Both species of native oak may suffer from Acute Oak Decline (AOD) which causes stem bleeding and rapid dieback and death in mature trees. Chronic oak decline also causes foliage deterioration but may take many years to kill a tree.

Knopper gall causes acorns to deform and lose viability. The high insect load of oaks can cause problems of heavy defoliation. Caterpillars of the green oak tortrix and the winter moth can completely defoliate trees in early spring. The oak processionary moth is also a major defoliator of oak.

A disease known in the USA as ‘sudden oak death’ caused by a fungus organism Phytophthora ramorum found on rhododendron is present in the UK but, to date, our native oaks are not affected.

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Oak logs

Sessile oak
Quercus petraea

Sessile oak tree

Sessile oak leaves

Sessile oak flowers

Sessile oak (Quercus petraea) is a deciduous tree able to reach heights of 40m and flowering April to May.

Sessile oak has subtly different characteristics from pedunculate. It has straighter branches radiating from a more upright trunk. Leaves have longer stalks (1–2cm) and the leaf bases do not have rounded lobes (auricles) but are wedge shaped. The leaf is widest above its centre point and its underside has hairs in the vein axils. Acorns are almost stalkless on twigs.

Hybrids between pedunculate and sessile oak can be found and are hard to identify; often having rounded leaf auricles but with long leaf stalks.

Sessile oak is native to the UK and, although its range overlaps with pedunculate, it is more common in the north and west on less fertile, more acidic soils at higher elevations. Its natural range has been distorted by planting. It is suited to well-drained soils and can cope on drier sites. It does not tolerate waterlogging.

Sessile is the more common oak species found in upland oak woodland (a priority habitat under the UK Biodiversity Action Plan). The habitat is rich in mosses, lichens and liverworts; many of which have species action plans. There are distinct breeding bird assemblages of redstarts, wood warblers and pied flycatchers and rare insects such as the blue ground beetle and the high brown fritillary and chequered skipper butterflies.

Growing advice as per pedunculate oak.

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Photographs © Forestry Commission