Platanus x acerifolia

The London plane so called because it is widely planted in the London streets and squares, has a curious ancestry. No planes are native to Britain, but early in the 17th century gardeners introduced the Oriental plane, Platanus orientahs, from Asia Minor, and about the same time the American plane, P. occidentalis, was brought in from the eastern states of North America. The American plane is not hardy in Britain: the Oriental plane can be very large and is occasionally seen in gardens, and seldom sets seed. About 1675, botanists noticed a new race of planes of exceptional vigour and hardiness, which had apparently arisen through chance cross-breeding between the two sorts. Nobody can now say where this happened, probably in southern France or in

Spain. London plane is usually increased by cuttings, although it sets fertile seed. Seedlings may resemble one or the other of their original parent trees, or show intermediate characters.

The plane is easily recognised in winter by the unusual shape of its buds. They are set alternately on the twigs and are conical in outline, rather like a dunce's cap; only one outer scale can be seen, and there is a scar at its base that almost completely encircles the bud This scar marks the point of detachment of a leaf-stalk. The plane's leaf-stalk has a swollen base which conceals the young bud that is growing beneath it - a rare feature that aids recognition.

Platanus Hispanica Bud

FIGURE 4S

Winter twig of plane, showing angular trend and ribbing below the alternately-set buds (life size).

Right: a single bud showing the conical shape and the scar of last-year's leaf-stalk base, which almost encircles the bud's base (X5),

Plane leaves are distinctly stalked and broadly lobed with from three to seven lobes: they have a resemblance to those of the sycamore {Acer pseudoph tan us, see Figures 5 and 6). in America, the name 'sycamore' is often applied to the native planes, whilst in Scodand the name 'plane' is frequently used for sycamore, that is Acer, trees. But the alternate arrangement of leaves and buds marks out the true planes distincdy. A main vein runs out to each lobe, and ends in a pointed tip. The leaves are light-green in colour and fade to a rich brown in autumn; they are leathery in texture and persist on the ground long through the winter.

Young twigs and branches have an olive-grey bark, but as the trunk and main stems mature they shed their outer bark in large flakes and reveal pale creamy-yellow patches of fresh bark below. This results in an unusual, easily recognised and gaily dappled tree trunk, for the process is repeated in different places throughout the life of the tree. In this way the plane rids itself of old bark in which the vital breathing pores, or lenticels, are becoming dogged with soot Even the trunks of trees must breathe in oxygen, and the bark-shedding habit helps the tree to survive in smoky towns, though late leafing and early leaf-fall are more significant.

Planes bear male and female flowers on the same tree, but in separate dusters, or inflorescences. They open in May and the two sexes look much alike. Each inflorescence is a round ball or bobble' set on a long hanging stalk; there may be two or three bobbles placed at intervals along the same stalk. The male inflorescence is a globular structure of small flowers, each no more than a duster of three to four minute green sepals, and a like number of minute green petals and well-developed stamens; the anthers scatter pollen on the wind and then the whole male flower group falls away.

The femde bobbles hold scores of very simple flowers, each having a cluster of three to four bract-like sepals and petals at the base, topped by four carpels having single styles and stigmas. After pollination, the whole bobble changes from green to brown; it is ripe by autumn and during the winter it gradually breaks up. Each little fruit falls away from the central stalk and ts carried away by the wind. It consists of four nut-like seeds, each carrying a tuft of fine yellow hairs. The drifts of plane seed look untidy and some people find the hairs irritate their eyes, but these are the plane's only faults.

Most seed proves fertile and where seedlings arise they are

FIGURE 49

Leaves and flowers of plane in May (Xj). with sections of male and female inflorescences (xlj). Each leaf has three to seven irregular lobes. Male flowers (left) grown in series of bundles or 'bobbies ; each has three to four sepals, petals and stamens. Female flowers (right) grow in an outwardly similar series of bundles on a separate stalk; each has three to four sepals, petals, and carpels.

easily identified. Each has a pair of sickle shaped seed-leaves, arched back from the central stalk; the early true leaves are simple in outline; lobed leaves appear later.

The timber of plane has a general resemblance to beech, being fawn in colour, hard, strong, and easily worked in any direction. It is not naturally durable out of doors. The small amount available is usually applied to indoor uses, such as high-class furniture or wood carving. Large logs are cut into.veneers, by methods that expose the lively figure of the pith rays, and because of the intricate pattern then revealed, these veneers are sold as 'lacewood.'

Plane has proved the most satisfactory of all trees for street planting in London and other large cities of southern England, and also in France, Spam, Italy and neighbouring lands. It grows vigorously under difficult conditions of polluted air and restricted root space, and is easily held to a limited size, where that is necessary, by repeated prunings. It forms a beautiful, well-balanced crown, which casts welcome shade on hot sunny days without itself appearing dark or gloomy, while its bark is a cheerful feature even in the winter months. Many trees in the London squares are now 200 years old, and have readied heights of 30m with girths of 3m. A fine tree in Carshalton, Surrey, by Festival Walk, is 39m tall arid 6.76m in girth (2,15m diameter) while that at the Bishops Palace. Ely, Cambridgeshire, perhaps an original dating from about 1675 is 35 X 8.74m (2.78m diameter).

figure 50

Plane seedling a few weeks after germination. The two seed-leaves are narrow and sickle-shaped, and the first true leaf is a simple one, scarcely lobed at all (xy)

FIGURE 51

Leaf, winter bud, and fruit dusters of plane in autumn (xl). Each flower has become a tiny rounded fruit that will shortly release a single seed, tipped with bristly hairs. The projecting points are the old flower-styles.

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