Monthly Archives: January 2015

Sleeping Hedgehog Trees

I have a love-hate relationship with London Planes. I grew up in London, and they are this city’s Familiar – over half of the trees here are Platanus x hispanica, and they are widely planted in other cities and towns too. I affectionately think of them as Sleeping Hedgehog Trees, as the seed balls remind me of curled up tiggies. But they are also, I’ve realised since becoming a gardener, a right pain in the neck!

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The origins of this iconic tree is contested, but it is commonly believed that it is a hybrid between the Eastern Plane and the American Sycamore (Platanus orientalis P. occidentalis). The first in London were planted in Berkeley Square in the 17th century. Whatever the origins of the London Plane, it’s quite startling to find out  that the Platanus genus is close kin of the Sacred Lotus (Nelumbo nucifera), an aquatic perennial that was thought to be closely related to the Water Lily. DNA analysis at Kew’s Jodrell laboratory has revealed their connection, and their independent phylogenesis suggests that Platanus and Nelumbo could be remnants of an larger, mostly extinct, group of plants: the Sacred Lotus and the Plane might well be living fossils.

For centuries, flower similarities was the way in which plants were classified, but those of the Plane appear very different to the blooms of the Sacred Lotus. The flowers of the Plane are held in spherical clusters, in pendulous congregations of 2 – 6. Each flower cluster is either male or female: the male is yellow-green, the female is scarlet, resembling a sea anemone. The resulting seed balls remain on the tree throughout winter, dispersing their achenes in spring which ride the breezes by means of hairs acting like parachutes.

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Therein lurks the reason for my partial dislike of this tree: hair! Along with fluff from the seeds, the juvenile leaves are downy. This hair is shed as the foliage matures and breaks up into teeny-tiny particles which cause irritation. I’m not an allergy sufferer but this affects even me. It’s more a physical reaction than an allergy, like getting dust up your nose. Yet I only really noticed when I started working in London squares which have quite a high concentration of Planes. On a blustery day in May or June, it will cause eyes and throat to itch, and if these motes are inhaled, they can hang round your uvula provoking coughing fits which make you feel as if you’re going to cough yourself inside out! If you think I’m being a drama queen, the agitation of these particles on the eyes and respiratory system has been written about since ancient times, by Galen and Dioscorides for example. But this has not stopped the tree from being planted, as  they are tough as old boots and rather majestic, if not pretty.

The reasons for its success as an urban tree is the London Planes’ tolerance of pollution, drought, soil compaction and heavy pruning (‘topping and lopping’). Its method for dealing with pollution is to slough off its scaly bark. Other agents of bark-peel is the woodpecker. A tell-tale sign that one of these drillers have visited is a ring of bark flakes around the base of the trunk. Presumably the birds have chipped away in search of insects. The knobbles and bobbles, cracks, flakes and scales that can be found on the trunk all make perfect hiding places for critters, including funnel web spiders and woodlice.

Tough as it is, Platanus hispanica is not without health problems. For decades, the capital’s London Planes have suffered a fungal disease called Anthracnose. (The American Sycamore is highly susceptible, whereas the Oriental Plane is fairly resistant.) There are several symptoms, but the most obvious to me has been leaf blight. This is where brown necrotic patches form along the main leaf veins. Leaf-fall then occurs in the green, causing more headaches for those of us tending gardens in the shade of Planes. It makes it difficult to do proper gardening when having to tidy up the detritus of these trees – there simply isn’t enough time! I’m no spic-and-span gardener, but if you didn’t clear the fluff, seeds and green leaves that fall in early summer, the gardens wouldn’t be pleasant places to enter.

Recently, another fungal disease affecting Planes has reached our shores: Massaria (Splanchnonema platani). The overall health of the trees aren’t badly affected but the fungus can cause large limbs to drop. Ironically, it seems to affect those trees which are drought stressed, one of the very conditions that Planes have been good at withstanding. The biggest problem to the Plane population, however, may not be the disease itself but “a disproportionate response.. driven through fear of an over exaggerated perception of public safety risk”. The London Tree Officers Association assert that though Massaria poses a challenge to those responsible for trees and public safety, it can be managed within existing management procedures.

I can’t end this post without mention of my favourite Plane tree – the Weeping Plane in Chester Square. A look at its trunk informs us that this is a graft specimen – the texture of the bark abruptly changes at around shoulder height – but its parentage is unknown. It has branches which are squiggly and undulating, and is attractive in the way that all lachrymose trees seem to be.

Love them or hate them (or both in equal measure), it would be difficult to imagine London without its namesake Planes.

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Further Reading:

W.J. Bean, Trees and Shrubs in the British Isles, John Murray 1976 (8th edition, revised: 1981)

Richard Mabey, Flora Britannica, Chatto & Windus, 1997

Bob Press & David Hoskin, Trees of Britain & Europe, New Holland,1992

http://www.ltoa.org.uk

http://www.kew.org

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