Quercus robur

Pedunculate oak is distinguished from the Sessile oak by its female flowers and acomsbeing set on long stalks, and also by its almost stalkless leaves. It is probably the commoner of our two native oaks, and may in fact be our commonest tree. A Forestry Commission census of trees and woods taken in 1947 showed that at that date, oaks occupied one third of the woodland area, while every third tree along the hedgerows was also an oak. This shows how well adapted the oaks are to the British climate and to most of our varied soils, though you will not find them on the poorest land, nor in exposed places amid the hills.

Oakwoods are still being planted today, though only on a modest scale. This is because oak takes so long to mature, and is slow to produce any considerable volume of marketable timber. The smaller sizes of oak timber, such as that from young trees removed from plantations during thinnings, or from mature trees holding much branchwood, fetch tow prices. But large, straight stems are always valuable, though they take 100 years or more to mature. Most of them are sawn into planking which is used for high-class joinery and furniture. Some are cut or sliced along the radius or 'true quarter' of the log, to expose the beautiful silver grain which is used as a surface veneer over ordinary timbers.

Forest oaks begin Ufe as sturdy seedlings in a nursery bed. Their large seed the acorn, enables them to put down a long tap root and to send up a sturdy shoot in their first season. They may be planted in the woods at that age. or else be transplanted to another nursery bed, where they spend a second year, growing larger and developing a more bushy root system. In the woods they are planted about 1,25m apart, rather closer than other trees, to encourage early upward growth, and to discourage side branching in their youth. Close spacing also provides a surplus of trees for removal as thinnings, leaving the better ones to remain to form the final crop of mature timber. For the first few years an oak plantation looks rather scrubby, for the little trees start growth slowly and need repeated weedings each summer. By degrees a large proportion develops into tall straight poles. As they grow larger the survivors from the thinnings develop large, spreading crowns and start to bear flowers and seed. Eventually, perhaps 120 years after planting, the whole stand is felled for the sawmill, and the land is replanted.

The annual rhythm of life for the oak begins in April, when the buds burst and the stSSt green leaves, tinged with brownish red, expand The shoot buds elongate to give the first extension of the tree's branchwood. Later in the season there is a second, further extension that is very characteristic of the oak, though it is also found in beech and many other trees. This is called 'Lammas growth' because it is most marked in midsummer though Lammas Day is actually the first of August At that time long shoots, carrying rapidly-expanding leaves which are, at first crimson in colour, grow out and extend the crown.

figure 80

figure 51

Flowering twig of Pedunculate oak (life size) showing two groups of female flowers, on long stalks, at the left, and male catkins in the centre. Lower left; Two female flowers on their long stalk (X7); each has a cluster of bracts and a three-styled pistil.

Lower right Two male flowers on their catkin stalk; each is a bundle of bracts and stamens.

Open-grown oaks often bear catkins and fruits while quite young, no more than 20 years old. hut in the woods flowering is usually delayed until the trees have stood for 40 years or so. Catkins open in May, just after the leaves have expanded, and acorns ripen in October. In a mild autumn they start to sprout at once, but those that are needed for sowing by the forester are stored through the winter in cool moist surroundings, such as a weD-ventilated earth pit. protected from the rain and from marauding birds or squirrels.

The oak's active year ends with the fall of the leaves, which fade to bright brown as winter approaches.

Oaks are remarkable in being able to endure a variety of fungal diseases and insect plagues without suffering lasting harm. The most conspicuous types of damage are the galls formed by small gall-wasps that lay eggs in developing tissues. Abnormal growth results, and a tiny grub or larva grows up within the gall, feeding on the oak's substance. Common forms are the Marble gall, which forms in place of a shoot and is hard, brown and round, and the Oak-apple, a soft pinkish-white outgrowth on the leaves; there may also be quaint round Spangle-galls on the leaves. Currant-galls on the male catkins, and yet other galls below ground on the tree's roots. The Oak leaf roller moth Tortrix viridana, so called because its grub rolls over the leaf so that it can pupate beneath it. may become so numerous that its voracious caterpillars strip nearly every leaf from a whole wood. But the oaks survive such mishaps with only a small decrease in annual growth.

Individual trees can reach great girths, the present record being held by a Common oak in Lincolnshire 12m round (3.78m diameter}. Trees of this size are always very hollow and cannot be estimated for age at all closely, but a few may be 500 years old. Oak is not among our tallest trees: the height record. 42,5m is held by a Sessile tree at Whitfield in Herefordshire, has been exceeded by lime and poplar. The tallest Common oak found is 41m at Leeds Castle. Kent.

FIGURE 82

Fruiting twig of Pedunculate oak the atoms are oblong, becoming broader towards the tip, then tapering. The leaves are stalldess.

Was this article helpful?

0 0

Responses

  • Janina Schroeder
    How to find the age of Quercus robur?
    7 years ago

Post a comment