The plane tree is a particularly beautiful species of ornamental tree found in parks and cities in many parts of the world. It is commonly planted along boulevards and public walk-ways.
A London Plane-Tree - a poem by Amy Levy, 1889
Green is the plane-tree in the square,
The other trees are brown ;
They droop and pine for country air ;
The plane-tree loves the town.
Here from my garret-pane, I mark
The plane-tree bud and blow,
Shed her recuperative bark,
And spread her shade below.
Among her branches, in and out,
The city breezes play ;
The dun fog wraps her round about ;
Above, the smoke curls grey.
Others the country take for choice,
And hold the town in scorn ;
But she has listened to the voice
On city breezes borne.
The first time I became aware of the plane tree was while walking through Bristol, where they are planted along the river's edge and around Queens Square. The leaves are shaped like sycamore or maple leaves; the trunk is incredibly beautiful, if you take the time to study it, with dappled, flaking bark coloured green through yellows to brown. The fruits of the plane tree hang like hairy baubles, 1 - 2 inches (5cm) in diameter, and they remain throughout the winter.
The plane tree belongs to the genus Platanus (which includes the sycamore) and fossils have been found which date back over 100 million years. There are ten species in this genus, all found in the northern hemisphere. Species include Platanus occidentalis (from Eastern USA), Platanus orientalis (from SE Europe) and Platanus kerrii (from Indo-china).
In England, the most frequently seen variety is called the London Plane Tree. It is hardy and stands up well to the polluted air found in urban areas. Pollution and smog were more of a problem a hundred years ago than today, due to the widespread use of coal. Young trees planted at that time therefore needed to be strong enough to flourish in that environment.
The London Plane tree, distinguishable by its leaf shape and bark, grows to about 50m tall. It is thought to be a hybrid of P.orientalis x P. occidentalis, which probably occurred spontaneously in the 17th century, and is often referred to as Platanus x acerifolia. The leaves are palmate, veined and the underside is covered with a fine down, especially when they are young, which sometimes causes asthma and hayfever in susceptible individuals. The tree bears seperate male and female flowers which are wind pollinated. Each female flower becomes an achene, a number of which cluster together to form the spherical fruit; 2 - 4 fruits may hang from a single twig.
Diseases
Unfortunately plane trees are susceptible to fungal cankers. It is estimated that in the last 20 years 25,000 plane trees have been lost to canker stain (caused by the fungus Ceratocylis fimbriata ) in the south east of France alone. The disease was brought to France by American troops during World War I. It infects trees through injuries to the trunks, branches and by root contact, and is rapidly spread by pruning with contaminated implements. Die-back occurs at the site of infection, and then spreads to the rest of the tree, killing it in 3 - 5 years. Research is ongoing to breed resistant hybrids in the hope that this magnificant tree will not be lost forever.
refs:www.inra.fr/Internet/Directions/DIC/PRESSE/juin01/gb/nb1.htm
http://www.chengappa.demon.co.uk/planes/index.htm
http://www.queensu.ca/pps/grounds/arboretum/London-planetree.htm