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PEDUNCULATE OAK

ENGLISH OAK

Quercus robur

Beech Family [Fagaceae]

month8apr month8april month8may

category
category8Trees
category
category8Broadleaf
category
category8Deciduous
status
statusZnative
flower
flower8green
inner
inner8cream
petals
petalsZ0
type
typeZcatkins
stem
stem8round
toxicity
toxicityZmedium
sex
sexZmonoecious

26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
A young tree, older ones can grow to 40m high, with a wide rugged trunk and a broad crown.


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
The leaves are oblong and usually broader at the base and with only a very short stalk (as opposed to the very similar Sessile Oak where the leaves are on longer stalks).


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
Lobes rounded (on Sessile Oak some lobes might be triangular at the end).


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
The underside of the leaves.


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
 The tree is monoecious with both male and female flowers on the same tree. The male flowers are in long greenish-yellow knobbly catkins.


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
 Male catkins are between 2 and 4cm long with each flower having 6-8 stamens (up to a max of 12 stamens).


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
 Male flowers with each flower having 6-8 stamens (up to a max of 12 stamens).


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
 Male flowers yet to open.


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
The brown 'scales' near the male catkins.


26th April 2014, woodland, Runcorn East, Cheshire Photo: © RWD
Trunk is grey-brown with fissures.


Easily mistaken for : Sessile Oak (Quercus petraea) but that has leaves which are a similar dark-green on the upper surface, with a sparse covering of hairs (rather than hairless), the leaves are stalked (rather than usually only short-stalked), and the lobes are sometimes pointed at the end (as opposed to rounded), and the acorns are totally un-stalked (as opposed to stalks up to 10cm long on Pedunculate Oak).

Hybridises with : Sessile Oak (Quercus petraea) to become Quercus × rosaceae Grows best on damp rich and well-drained soils in woods, especially on lime. It is native but is often planted in hedges and parks. Some specimens can live to 1000 years developing a massive girth. The fruit, the acorn nut, is borne on stalk which is up to 10cm long (un-like those of Sessile Oak which are on attached directly to the base without a stalk).

NEEDED : Female flowers, Acorns.

OAK GALLS

There are many differing galls on Oak trees, the most commonly seen is the Oak Marble Gall

Oak Marble Gall (harbouring Andricus kollari)

These are spherical and about the size of a marble, up to 20mm across which grow on stems and buds. They are green when first formed in the spring but quickly turn a pale brown and become very hard, frequently remaining attached to the tree for several years means that they are easily seen. They house the larvae of one gall wasp Andricus kollari and possibly several other squatter species. When the larvae is mature they escape through the hard woody sphere by tiny holes (photo below) which look like woodworm holes.

They are hard and yield Tannic Acid used for various applications (see below).

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Common Spangle Gall (harbouring Neuroterus quercusbaccarum)

Inhabiting the underside of Oak leaves and exhibiting the classic flying-saucer shape, these are flattish circular discs about 5mm in diameter with a raised dimple in the centre. These are the asexual generation of the gall wasp Neuroterus quercusbaccarum. Scattered around the visible surface are tufts of reddish-brown hairs, sometimes dense as those in the upper right.

Having a central stalk with side-branches the hairs are like tiny coniferous trees. These galls fall off the leaves passing the winter in the leaf litter below the tree, swelling as the insects mature to emerge as adult wasps early in the spring, to lay their eggs in the buds of oak.

The sexual generation of the same gall wasp, commonly known as current galls, develop on the male catkins of Oak (here Pedunculus Oak) (or on young leaves) and are spheroidal in shape, about 6mm diameter, soft and squishy, juicy and green with reddish-brown marbling on the surface (shown below). They mature into wasps in late spring to early summer. Mated female wasps lay their eggs in the leaves to begin the cycle again.

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Silk Button Spangle Gall (harbouring Neuroterus numismalis)

Mixed in with the above Common Spangle Galls are Silk Button Spangle Galls which are small doughnut shaped torus up to 5mm across, but here noticeable smaller than the Common Spangled Galls it nestles amongst and with which it is concolorous. These are the galls of a similar wasp, Neuroterus numismalis and also develop on the underside of Oak leaves. Like those, they mature on the ground in autumn amidst leaf litter to emerge in the spring as an adult wasp. The eggs of this wasp are similarly lain in the buds of Oak trees, this being the sexual generation, where the galls are far harder to spot being green buttons with a central dimple and with radiating paler-green lines (no photo), this larvae will pupate within the gall to emerge between May and July.

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Oak Cherry Gall (harbouring Cynips quercusfolli

Similar size and appearance to Oak Marble Gall (about 20mm diameter)

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Striped Pea Gall (harbouring Cynips longiventris

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Pea Gall (harbouring Cynips divisa

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A Gall (harbouring Neuroterus saliens

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Cupped Spangle Gall (harbouring Neuroterus tricolor

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Smooth Spangle Gall (harbouring Neuroterus albipes

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An Oak Gall (harbouring Neuroterus politus

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Kidney Gall & Waxy Pin Gall (harbouring Trigonaspis megaptera

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A Gall (harbouring Macrodiplosis pustularis

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A Gall (harbouring the gall midge Macrodiplosis roboris

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Oak Apple Gall (harbouring Biorhiza pallida

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Acorn Cup Gall (harbouring Andricus grossulariae

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Acorn Knopper Gall (harbouring Andricus quercus calicis

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Ram's Horn Oak Gall (harbouring Andricus aries

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An Oak Gall (harbouring Andricus corruptrix

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An Oak Gall (harbouring Andricus inflator

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An Oak Galll (harbouring Andricus feccundatrix

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An Oak Gall (harbouring Andricus curvator

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An Oak Gall (harbouring Andricus quadrilineatus

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Cola Nut Oak Gall (harbouring Andricus lignicolus

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An Oak Gall (harbouring Andricus sieboldi

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Hedgehog Gall (harbouring Andricus lucidus

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An Oak Gall (harbouring Andricus grossulariae


An Oak Gall (harbouring Andricus quercusramuli

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An Oak Gall (harbouring Andricus malpighi

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An Oak Gall (harbouring Andricus callidoma

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An Oak Gall (harbouring Andricus seminationis

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An Oak Gall (harbouring Aphelonyx cerricola

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Oak Apple Gall (harbouring Biorhiza pallida

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A Current Gall (harbouring Neuroterus quercusbaccarum

GALLOTANNIN and TANNINS


GalloTannin is one of the tannins found in the bark of Oak Trees which is also present in toxic proportions in the Acorns. It is toxic to horses who eat the acorns on the ground and may kill them or impart seriously injury, but pigs are oblivious to the toxin and can eat the acorns with impunity without ill effect, which is why sometimes pigs are set free to gobble up all the acorns under trees in a field before the horses are allowed into that field.

GalloTannin is centred around a single molecule of Glucose (shown in red), surrounded by five concatenated pairs of Gallic Acid, ten in all. It is a free-radical scavenger, mopping up dangerous charged partial molecules of other substances such as occur when chemical reactions are taking place (which includes those occurring within the body).

Your Author is quite proud of his neat quasi-symmetrical drawing of GalloTannin, the reader should see the messy contorted drawings of it to be found on the internet!

Unlike GalloTannin (which is Decagalloyl Glucose with 10 units of Gallic Acid) Tannic Acid is not a single compound but is instead a mixture of many differing Polygalloyl glucoses, with each molecule containing between 2 and 12 units of Gallic Acid arranged haphazardly. GalloTannin is just one of the components which could be in Tannic Acid. Although Tannic Acid is a tannin, (natural plant polyphenols), it is not the Tannin in tea (which consists of a plethora of differing polyphenols).

Oak trees are not the only plants to contain Tannic Acid, the gall nuts of Rhus semialata and the leaves of Sicilian Sumac (Rhus coniara) both posses their own admixture of Polygalloyl Quinic Acid Esters).

The Tannic Acid found in the bark and leaves of Oak trees actually has only two components, GalloTannin and QuerciTannic Acid (whose structure is not to be found on the internet but is said to be a mixture of Polygalloyl Quinic Acid Esters, whilst that found in Oak Galls just one, GalloTannin, according to sources on the internet, which are a bit garbled.

Tannic Acid (the mixture) is highly soluble in water and is slightly acidic with a pKa of about 10.

The Tannic Acid extracted from Oak Galls was made into ink for fountain pens by reacting it with iron in the form of ferrous sulfate FeSO4 (aka Green Vitriol and known since ancient times as Copperas - although as can be seen by the formula it contains no copper) and were known as Iron Gall inks aka Ferro Gallic inks. The Ferrous Sufate is found as the minerals Szomolnokite and as Rozenite (both with 4 molecules of water of crystallization), as the rarer Sidereotil (with 5 units) and as the more common Melanterite (with 7 units of water of crystallization). This kind of ink was in use for 700 years, when a quill was the writing implement. But a great disadvantage with this 'ink' is that it is colourless and clear until it has reacted with the fibres in the paper - when a black iron compound (Ferric Tannate) forms. This dark compound is highly resilient and will remain there for a long time, it is thus an excellent ink for archival purposes, although this fact was not necessarily appreciated at the time. However, it was not easy to write with what is at first an invisible ink! In order to to combat this invisibility problem a blue aniline dye was added to the ink to make it visibly blue. Upon drying it turns almost black, a dark bluish-black, and this ink was called 'Blue-Black Ink' because it turns from blue to black as it chemically reacts with the paper whilst drying.

Tannic Acid was also used for dying textiles as well as tanning leather, although many differing un-related substances have in the past been used to tan leather.

Tannic Acid, mixed with an organic polymer and 2-ButoxyEthanol, is also used as a rust remover. Applied to rust it forms the bluish-black Ferric Tannate which will clean off easily.

See also Ellagitannins.


  Quercus robur  ⇐ Global Aspect ⇒ Fagaceae  

Distribution
 family8Beech family8Fagaceae

 BSBI maps
genus8Quercus
Quercus
(Oaks)

PEDUNCULATE OAK

ENGLISH OAK

Quercus robur

Beech Family [Fagaceae]