In these last green weeks before nature’s traffic lights turn the trees to red and amber, there is little visible sign among them of the effects of a droughty summer. Though the garden rain gauge registered just 8mm of rainfall in 10 weeks from the end of May, it poured all through August, a daily deluge of birch seeds that filled every crack and cranny and clogged the spiders’ webs with vegetarian fare.
Drought-stressed silver birches cast unprecedented numbers of offspring into the wind, limes launched innumerable helicopter seeds to fall on parched soil, and oaks did not appear to even attempt their late summer spurt of Lammas growth. But in the autumnal reckoning, it appears to be photosynthesis as usual.
A terrible exception with a plague-struck appearance stands on Thorncote Green and in a million other places. The horse chestnut has gone into moth-induced winter, its rust-brown foliage the colour of death and decay. The giant leaves, which unfurled and splayed in spring into shapes like the feet of prehistoric birds, have curled up their toes. Thousands litter the ground in a premonition of December. The wrinkled, crinkled survivors – barely surviving – hang on.
Four hundred years after the horse chestnut was introduced to Britain, a new species to science, Cameraria ohridella, a leaf-miner moth, followed it from the Balkans. The female lays her eggs into chestnut leaves and there the hatched larvae stay, as if they were sealed in an envelope, eating their way through the contents. Blue tits are among the most assiduous of bug hunters in the canopy, yet they are only able to take less than one in 20. The tough skin that protects the chlorophyll factory cocoons its parasite, its nemesis. The carpet of fallen leaves contains pupae of next spring’s first generation, ready then to ascend the trunk and begin their feasting.
About a decade ago, when the miner reached this area and blighted trees all around, I noticed this big specimen on the green was still green. Some authorities suggested that gathering and burning all the leaves beneath a tree might prevent it being affected. Caterpillars crawl but moths can fly, and I judged it a futile task. But I wish I had tried.
