This tree, commonly called the London plane is usually considered to be an interspecific hybrid between Platanus orientalis and Platanus occidentalis. The tree is also known by the synonyms Platanus x hispanica and sometimes as Platanus x hybrida. Most trees in London belong to this species.
William Jackson Bean, in 'Trees and shrubs hardy in the British Isles' uses the term 'London plane' to refer to a single distinctive clone commonly found in some parts of London. Since the common name is generally used elsewhere to refer to all forms of the hybrid, I refer to this distinct clone as the 'London' (previously on this website this clone was described as the 'London Form'). A detailed description of this variety can be found here. An account of the use of the name 'London plane' is given on the botany page at this website.
There are several other clones and varieties that belong to this species, but these are not included here, as no specimens of them have been identified in cultivation in London. In addition, some authorities consider that some varieties thought to be of the Oriental plane Platanus orientalis may actually belong to this species.
Tree - It makes a large tree, usually strong growing in London, often with a single clear stem to some height. However, the crown shape and branching patterns can vary between the varieties on mature trees.
Bark - This often flakes off in patches in all wood more than a few years old, leaving a dappled trunk. In some forms the bark is not shed freely, and the trunk becomes rugged, though flaking continues on younger wood. In some varieties, such as 'Pyramidalis', the bark becomes rugged below the joins of major branches, and sometimes on the undersides of large branches.
Crown - The branching pattern is variable. Most often sinuous branches are found, but sometimes they are fairly straight. In some forms the tips of the branches are pendulous.
Shoot and young leaves - These are covered in down. They are moderately affected by anthracnose and early leaves are often damaged by this.
Leaf shape - Leaves are variable in shape, even on the same tree. They usually have 5 or 7 palmate lobes, central lobe usually as long as wide, sometimes longer. There are few to many teeth on each lobe, depending on variety. Some leaves have no teeth and the lobe has sinuate margins. The leaf base is varied, truncate to cordate. Down is retained on veins and axils on the undersides of leaves.
Leaf colour - This varies from medium to dark green, paler below, matt to glossy on the upper part of the leaf. The leaves may be appear to be yellowish or somewhat golden, especially on young trees.
Fruits - Flowers and fruit are borne in groups of 1-4 on a stem on short lateral growths. They can be up to 45 mm across, depending on variety.
The range of variation in this hybrid species is significant. Probably because of crossbreeding with Platanus orientalis a range of forms that merge gradually into this parent can be found. Some forms (such as 'Pyramidalis') are quite close to the American plane. Some of the variants currently listed under Platanus orientalis may be the result of back-crossing with this hybrid.
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