Plane trees of London

Identifying planes

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Distinct forms of plane tree can be very close to each other in their gross characteristics. It is possible sometimes to identify a tree from a single character. To identify trees reliably in general though, it is necessary to see many characteristics of a tree.

More detailed descriptions of specific characteristics can be found under the names of the individual trees.

Tree crown and shape

Tree shapes can be used as a diagnostic, though this should always be confirmed by looking at other characters. The characteristic shapes for most trees can be clearly seen only in mature specimens, which means at least 50 years old, with a century age being better yet. Be sure that the tree has not been pollarded or had its crown otherwise shaped in the past, as this will usually distort the shape beyond recognition. Many forms have branches with a sinuous or contorted habit; however, if they have been pollarded, it is common for straight branches to radiate out from the pollard points. Once it starts growing at normal rates, the younger branches may regain the sinuous habit.

Multiple stemmed and low branched crowns are characteristic of many forms of Platanus orientalis, though this variable species may sometimes be seen as tall specimens on a clean trunk, especially if crowded.

An angular branching habit with straight branches is typical of Platanus x acerifolia 'Pyramidalis'; this growth pattern is probably shared by many unnamed clones of Platanus x acerifolia.

High crowns on tall single trunks with a sinuous or contorted branching pattern are usually Platanus x acerifolia forms, including 'London' and 'Westminster'. This shape is also found with Platanus x acerifolia 'Augustine Henry', though this clone is even more distinctive with a tendency to form a straight and cylindrical trunk.

The unnamed clones can have all habits intermediate between Pyramidalis and the London Form.

Fruit

These can vary on a single tree but there are some distinct differences in size and number between varieties.

Large fruits; up to 45 mm across, borne 1 or 2 on a stem are characteristic of Platanus x acerifolia 'Pyramidalis'. Similar large fruits are also seen in the Platanus orientalis 'Hackney', but they then are 2, 3 or sometimes 4 on a stem.

Medium sized fruits, borne 1 to 4 per stem, with fruits to about 30 mm across, are found in most forms of Platanus x acerifolia .

Many smaller fruits on a stem, generally 2 to 6 per stem (though 3-4 is most usual), and fruits up to about 25 mm across indicates Platanus orientalis.

Fruits scarce on a mature tree, generally rather small, 1 to 3 per stem; often Platanus x acerifolia 'Augustine Henry'.

Leaves

When considering leaf shapes and sizes, it is necessary to make sure that the leaves are typical. Leaves on vigorous fast growing wood such as those on sucker growths, from recently pruned branches or on young trees on rich soils will be atypical, often much larger than usual. Leaves on old weak or dying trees will also be atypical. Leaves also vary in shape through the season, and it is usually best to avoid early leaves and late leaves; typically the third to fifth leaves on an extension shoot will be typical.

The typical medium sized lobes of the leaves of Platanus x acerifolia can be taken as a standard.

Long lobes, especially in the central lobe, may indicate either Platanus orientalis or its forms, and probably also back-crosses of the hybrid plane with Platanus orientalis.

Broad main lobes indicate Platanus occidentalis, sometimes hybrid planes close to it such as Platanus x acerifolia 'Pyramidalis'.

Long finger-like lobes are usually Platanus orientalis 'Digitata'.

Variegated leaves are usually Platanus x acerifolia 'Suttnerii', though there are other variegated forms.

Large thin leaves, often with numerous teeth are typical of Platanus x acerifolia 'Augustine Henry'. The blade of the leaf folds or droops when the leaf is held horizontally. This type of leaf can however sometimes be found in vigorous young growth of many types of London plane.

Leaf colour can sometimes provide some clues, especially in comparisons between neighbouring trees. Platanus x acerifolia 'Pyramidalis' has a distinctive deep glossy green leaf, most other forms being a medium green and not so glossy. Platanus orientalis 'Hackney' has a grey brown tinge to the leaves from a distance.

The table below shows gross variations in leaf shape between the three main species

Tree Number of distinct leaf lobes Central lobe
Platanus occidentalis 3-5 lobe is usually wider than long
Platanus x acerifolia 5, rarely 3 or 7. lobe is usually about as wide as long
Platanus orientalis 5-7 lobe always longer than wide

The texture of the leaves can be a good first guide to the cultivar when seen from a distance in summer.

Leaf buds

Long dark red-purple pointed buds, usually conical in shape - Platanus x acerifolia 'Augustine Henry' usually. While some other clones also have conical pointed buds, the buds are longest and most beech-bud like in Platanus x acerifolia 'Augustine Henry'.

Long large ovoid greenish purple buds - Platanus orientalis (some forms only) .

Ovoid buds, variable, sometimes with a blunt point, red to yellowish red - Platanus x acerifolia and many variants, Platanus orientalis and many variants.


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1-September-2009