Although rather small for a mature oak, this tree had the
appearance of being very old. Indeed, on certain soils or in
unfavourable climes, oaks will grow slowly and develop forms
considerably more stunted than this.
Click to explore a virtual oak
Right: a close-up view without the mist
(click image to enlarge).
Above: A drawing of an old oak pollard in Staverton Park, Suffolk,
England - taken from a photo by Gareth Lovett Jones appearing in the
beautiful book: The Wildwood, In search of Britain's ancient
forests, Gareth Lovett Jones and Richard Mabey (Aurum press). To the
Alchemists Nature was represented by a green dragon, breathing the
fire within itself. Can you see how the tree above may be likened to
(the Pedunculate or English Oak) and Quercus
(Sessile or Durmast Oak) are the two
species of oak native to the British isles. We shall focus on
these two examples here.
visible with a hand-lens in a cross-section) with multiseriate
rays (rays more than one cell wide) 0.3 to 0.55
mm wide and 2.5 cm deep and also uniseriate rays (one cell wide).
The sapwood is white, the heartwood golden
brown and very strong.
obovate (egg-shaped/oval with narrower end at the base and flat)
widest well above the middle and with
deep, irregular lobes (3-6 lobes on each side) with some veins
running to the sinuses (gaps) between the lobes.
petiole (leaf stalk) is very short (2 to 7 mm long) and auricles
present (small flaps of leaf blade either side of the petiole
not joined to it) and the leaf-base is narrow and cordate
(heart-shaped). The leaf is glabrous (hairless) except for a few
inconspicuous simple (unbranched) hairs on the lower lamina (leaf
blade) and midrib.
which species of oak did this leaf come from?
The lobing is not particularly deep, though the auricles at the
base are quite prominent and some veins run to the spaces between
the lobes, so this is likely a leaf from Q.
The differences are not always clear-cut, and many oaks are
also, leaf morphology varies according to the amount of sunlight
leaf is exposed to. In Q.
a dry atmosphere tends to produce
paler, duller and more deeply lobed leaves with more prominent
ovate leaves (oval and flat) with the widest point more-or-less in
the middle, but shade leaves tending to be
more obovate. The lobes are shallow and regular and number 5-8 per
side and there are no veins to the sinuses. The
petiole is longer (13-25 mm) and weakly auricled and often
tapering gradually to attach to the petiole. Long, clustered
hairs are clearly visible on the lower midrib and in the axils of
veins. The leaf-blade (lamina) also has tiny stellate
(star-shaped) hairs and the lower (abaxial) surface is often
downy. The leaves tend to be larger than those of Q. robur,
darker green and glossy on their upper surface.
flowers appear around mid-Spring (around may time) after the
breaking of bud dormancy. Separate male and
female catkins occur on the same tree. The male catkins are pale
green and the less conspicuous green
wind-pollinated female flowers occur in smaller groups of 2 or 3,
and have longer stalks in Q.
the stalks of the
female flowers of Q.
sometimes being absent.
acorns of Q.
are usually borne on longer hairless stalks (pedubcles) 2 to 9 cm
in length and the acorns
may be single or in clusters. The acorns of Q.
either lack stalks or are borne on shorter stalks 3-4 cm long
which bear clustered hairs. Acorn fall occurs in early autumn
(Sept / Oct). The mass of individual acorns varies up to
about 8.8 g, with the minimum viable mass about 0.5 g. Typically
about 20-30% of acorns are insect-damaged,
especially by acorn weevils. The smallest acorns are abortive and
contain no embryo.
grey-brown bark of Q.
is thick, firm and deeply fissured to form elongated
blocks/scales. The bark of Q.
is thinner and smoother with shallower fissures and in shorter
main trunk of Q.
is short as it tends to end in large branches such that the trunk
disappears into the crown.
Branching is irregular and the leaves and twigs are clustered,
resulting in quite an open crown. In Q.
and the is short as it tends to end in large branches such
that the trunk disappears into the crown.
foliage evenly spread to produce a dense crown. Mature oaks
typically reach 30-40 metres in height. ('Wiseman's
('Wiseman's Wood'?) in Dartmoor is an ancient Wood'?) in Dartmoor
is an ancient Q.
wood growing on
high, rocky ground wood growing on high, rocky ground
unsuitable as pasture. Under these harsh conditions the
oaks are stunted and extremely slow growing (and appear to still
be getting gradually taller) and the tallest trees
here, despite being many centuries old, are only 5 metres tall!
Their leaf-buds open much later in the year than
lowland oaks and their branches grow very long sideways from the
tree endlessly angled, twisted, raked, interlocked,
and reach quite as much downward as upward' and the trees
appear writhing and convulsed, reminiscent of bonsai
trees (John Fowles). The trunk of Q.
is often buttressed.
Oak trees live as long as 1000 years or so, with pollards tending
to live longer. A rough rule of thumb is that an oak
takes 300 years to fully mature, endures optimum health for a
further 300 years and then declines over 300 years.
However, repeated droughts can shorten the life span considerably.
Old (and drought-damaged) trees have
so-called 'stag's-head' crowns, with a mixture of living and dead
branches, with the dead branches, stripped of bark,
looking like the antlers of a deer stag. Oak trees first produce
fruit at about 30 to 50 years of age.
the germling, the tap
lengthens by 3 to 7 mm per day and is 20 to 30 cm long by the end
of the first year.
Only later on do radial or lateral roots (growing sideways) take
over and by 50 years of age the lateral
the main root system and they put out deeper vertical sinker roots to collect water from
the water table in times of
drought. The roots are 10 to 50 cm deep but spread up to 18
metres from the trunk by the age of 160 years.
Mycorrhiza are present with the
fungus mycelium clothing the outside of the root (ectotrophic) and
forming a Hartig
is primarily a lowland oak, preferring more basic and
nutrient-rich soils such as wet and heavy alluvial clays.
In contrast, Q.
is more of a highland oak, preferring well-drained and acidic
soils, such as sands, gravels,
granites, shales, sandstones and schists.
acorn is the fruit of the acorn and is a nut. A nut is a type of
achene with a hard and woody pericarp or fruit wall
and occurs in many other tree species, including chestnuts, beech
and hazel. An achene is a type of dry fruit which is
indehiscent (does not rupture when dry like a pea pod) formed from
a single carpel enclosing a single seed. The acorn
is derived from a trilocular ovary (an ovary with three
compartments) with two ovules in each locule, but almost always
only one ovule develops into a mature seed. The acorns of Q. robur are pale fawn or
olive-green with longitudinal
stripes and larger (~3.5 g). The acorn of Q.
is usually smaller (~2.5 g), rounder and dark brown with no
left, L.S. (longitudinal section) of a female flower of Quercus; right, T.S. (transverse
section) of female flower of
Quercus. The perianth (petals
and sepals) are thought to be sepals only, numbering 5 to 7
(forming the calyx, K). The
three carpels (collectively the gynaecium) are fused and inferior
(attached lower on the receptacle, or swollen end of
the flower stalk, than the stamens). The male flower has 5 to 7
more open sepals, no gynaecium and 6-12 anthers in
C 0 A 6-12 G 0.
Mature oak trees have large globular crowns, that of Quercus
robur being wider than that of Quercus petraea. The
Florida live oak, Quercus virbiniana, is a majestic tree
whose naturally sweeping branches made them ideal shapes for
shipbuiding. Most oaks require training of their branches and trunks
to achieve the right shapes. Old oak trees may lose vitality in
parts of their crown, especially after several years of drought,
with dead whitish branches, dead and stripped of bark, protruding
from the crown like 'antlers' to form a so-called 'stag's-head
tree'. This is beginning to happen to the tree in this
Another Pov-Ray model
28 Dec 2015
14 May 2019
18 May 2019
Above: Quercus robur. Plants are inspirational to both
scientists and artists alike, so before delving into the science of
oak trees, we shall ponder their aesthetic appeal. Below are some 3D
computer model oak trees generated in Pov-Ray with TomTree. I found
creating these graphics both artistic and scientifically relevant.
They are produced by tweaking a long list of parameters (with some
randomness thrown in by Pov-Ray's pseudo-random number generator). I
think I obtained a degree of success, though it should be remembered
that their are some 600 species of oak (Quercus) worldwide
and each species differs to some extent in its form.
A study of the form of a Pedunculate Oak (Quercus robur).