The London plane is the only plane tree found in the UK in appreciable quantity. It is very common because it’s especially suited to urban life, and so provides the greenery in many of our city centres. London planes form a backdrop to the capital’s most famous tourist attractions: they line the Mall leading to Buckingham Palace, they flank the entrance to St Paul’s Cathedral, stand guard over the Tower of London, and watch over Parliament. It is estimated that it accounts for at least half of the trees in London.
Yet the London plane does not occur naturally in the wild. It is thought to be a hybrid between two other species – the Oriental plane (Platanus orientalis), and the American sycamore (Platanus occidentalis). This hybridisation would not have occurred without human intervention because the parent species grow on separate continents – the Oriental plane is from eastern Europe and Asia, while the American sycamore is native to North America. The hybrid was first noted In the mid-seventeenth century, and is now called the London plane (Platanus × acerifolia) since it has been so widely planted in the city.
However, the London plane grows in cities all over the world – from Birmingham to New York to Sydney. It has many features that make it ideal for the urban environment. It is a tall and provides ample shade but if it grows too large it can be harshly pollarded without dying, and it still maintains an attractive shape afterwards when it re-grows. It will endure considerable heat and a moderate drought, yet withstand freezing winters and the compacted soils of a city. Finally, and most importantly, the London plane is not only tolerant of city pollution it will actively remove pollutants from the air – shedding toxins in its leaves and also in its bark which sloughs off in sheets throughout the year.
It is unclear where the London plane first came into being – the two leading potential locations being in Spain or in England. In England, the principal site usually put forward for the tree’s genesis is the Vauxhall Gardens belonging to plant collector, John Tradescant the younger, who certainly had access to specimens of both parents. It was Tradescant who first brought the American sycamore to England in 1636, while the Oriental plane had already been popular in the UK for at least a century. It is a romantic notion that London’s most popular tree could also have been born there.
Since the London plane is a relatively new creation, it is not yet known how long it lives, or how large it gets. The most ancient trees in the UK are accepted to be the two specimens given to Robert Sanderson, Bishop of Lincoln, in the early 1660s; they are still healthy and robust, and can be seen at Buckden Towers in Cambridgeshire. The oldest tree in London is at Barn Elms and dates from approximately 1685, but the oldest in central London are those in Berkeley Square which are held to have been planted there in 1789. In terms of size, the London plane generally does not often grow over 30 metres in cities, but there are three much more lofty examples at Bryanston in Dorset. The height of one of them was over 49 metres in 2015, making it one of the tallest broadleaved trees of any kind in Europe.