Dulwich is that rarity among London’s urban neighbourhoods - a built-up area that retains big forest trees at its residential heart -and few of these trees are bigger or more forest-like than the horse chestnut. Aesculus hippocastanum in full regalia is one of the spectacles of a late English spring - a kind of cross between a castle and a Christmas cake - and we would be inestimably poorer without it. Yet in recent years its disappearance has been seriously mooted.
The horse chestnut is a native of the Balkans that arrived in Britain in the 17th century and was much planted in Dulwich, as elsewhere, from the 18th and 19th centuries onwards. Particularly notable are the chestnuts of Dulwich Village and College Road, where road width an large gardens give them the space they need. But over the last decade the horse chestnut has faced a series of threats which have led to concerns about its survival prospects.
Larger trees are already at risk in cities because of higher human densities and a safety-first compensation culture. Horse chestnuts face a new threat from bleeding or weeping canker, a bacterium that causes dark, weeping stains and a rash of rust-coloured pock marks, along with cracks in the bark, which effectively become open sores. Forestry
Commission research in 2008 suggested that three-quarters of trees in the south-east are infected.
More familiar in Dulwich is the second major new threat, the horse chestnut leaf miner, a moth the size of a full stop which may well be an ancient enemy of the horse chestnut but only arrived from the Balkans in the UK (in Wimbledon) in 2002. The moth burrows into the leaves, making them shrivel and turn brown and subjecting the tree to water stress, and turned up en masse in Dulwich some three or four years ago, probably imported by some unwitting driver.
Early predictions of devastation have so far, however, proved unfounded. Forestry Commission reports indicate that some trees show signs of recovery from bleeding canker while Tony George, the Dulwich Estate’s arboricultural adviser, says the impact of the leaf miner moth has been diminishing over the last two years. Despite questions about whether Dulwich might be better served by trying other forms of (potentially moth-resistant) chestnut, the Estate, while it has planted some Indian chestnuts, is thus keeping faith with the “English” horse chestnut, at least in the village itself: it is, after all, tradition.