Tuesday, 1 November 2016


Oaks, i.e. Quercus species, belong to the Fagaceae, a family which includes beeches and the Sweet Chestnut. Just over 6oo species of Quercus are known, with a large proportion being found in North America; there are two species native to Britain, Quercus robur and Q. petraea, and two others, the Turkey Oak and the Holm Oak, are widely naturalised. In all cases the fruit consists of an acorn (Old English ac, an oak, and corn, a seed).
Here in the south midlands, and over the south of Britain generally, the commonest Quercus is the Pedunculate Oak, Quercus robur.  The word 'pedunculate' refers to the long slender stalk  - peduncle - upon which the acorns grow. It is found on deeper, often wettish, neutral to alkaline soils, and is found across Europe to the Caucasus and beyond.
Pedunculate Oak. The acorn is situated on a slender stalk. Kentle
Wood, Daventry. 29 October, 2016
The Sessile Oak, Quercus petraea, is commoner in the north and west of Britain. It is a tree of thinner, stony (the word 'petraea' is derived from the Greek petra, a rock) more acidic soils and will often be found quite high up in the hills. In Northamptonshire it is relatively uncommon but there are some acid grasslands in the west of the county and a visit to Newnham windmill produced a result.  Windmill Hill is capped with acid soil - bracken, tormentil and gorse are present - and there stood a Sessile Oak.

The distinctive leaves of Sessile Oak. Windwill Hill, Newnham,
Northants. 31 October, 2016
I was unable to find acorns but the leaf shape is characteristic. with the leaf-blade tapering down to the petiole. By contrast, in the case of the Pedunculate Oak the base of the leaf has a pair of lobes, often referred to as auricles.

Pedunculate oak showing (top of picture) the lobes at the
 leaf base. Daventry, 1 November, 2016

For centuries only one Quercus species was recognised in Britain but with care the differences are easy to see. The leaf of Pedunculate Oak shown below is covered my what I at first thought was sooty mould. I am now convinced that it shows the poo of Harlequin Ladybirds, of which there have been enormous numbers this summer.

Another view of a pedunculate oak leaf showing the lobes
 more clearly. Daventry, 1 November, 2016

It will surprise no one to find that the hybrid Quercus robur x Q. petraea (Q. x rosacea) can be quite frequent where their ranges overlap.
The Turkey Oak, Quercus cerris, can be instantly recognised when in fruit by the long scales on the cup.

Turkey Oak in the grounds of Danetre Hospital, Daventry.
26 October, 2016

These scales turn outward and the cup encloses roughly three quarters of the acorn.
The same tree, showing the acorn...

When not in fruit the leaves are quite distinctive, being relatively slender with up to ten rather pointed lobes on each side.

...and the leaves.
The Holm Oak, Quercus ilex, is sometimes simply referred to as the Ilex. (Our native holly is Ilex aquifolium and the pretty little Kermes Oak, Quercus coccifera, widespread around the Mediterranean, has rather spiny, holly-like leaves.) The Holm Oak is evergreen and not obviously an oak at all, until its acorns are noticed.
The glossy, evergreen leaves of the Holm Oak are
distinctive. Byfield Pocket Park, 29 October, 2016
A small grove of Holm Oak exists at the southern end of Byfield's pocket park and, after a good deal of searching, a couple of the rather small acorns were found.
The acorns of the Holm Oak are rather small. Byfield Pocket Park,
29 October, 2016

The tree is quite resistant to salty winds and has often been planted near to the sea. Many woodlands around Sheringham in Norfolk consist largely of Holm Oak and on the Isle of Wight it has become a pest, and a large-scale eradication program is now being undertaken. Incidentally, many of the leaves of the pocket park specimens displayed the mines of the common Garden Midget Moth, Phyllonorycter messaniella. It probably does little harm.
Holm Oak leaves showing the mines of the Garden Midget, a common
moth larva on oaks. Byfield Pocket Park, 29 October, 2016
Other exotic oaks may be found in collections from time to time - but I must not allow myself to go beyond the remit I have set myself.

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