22 NOVEMBER 1946, Page 17

Urban Parasites

Though we are continually being surprised by the plants and creatures seen in London, such as Canadian ragwort and black redstarts and libel- lulae, there are some common things that cannot live, much less flourish, in the town. The most surprising, perhaps, is lichen, which, of whatever sort, is killed by smoke, and attempts to raise even the commonest butterflies in the Parks—Battersea Park, for example—were altogether defeated by the hosts of parasites. In respect of the parasites, I have more than once been astonished to see quantities of parasitic hover-flies among the dahlias in the garden by Charing Cross. How do they breed in such a neighbourhood, from which the bees they mimic are almost wholly absent? An expert gardener in the East End of London told me he failed to persuade forget-me-nots to flourish, though I fancy others have succeeded. Contrarywise I never saw lilies of the valley do better than in a small and nearly sunless garden in Chelsea. In regard to trees, London may seem " a plane tale " to many, and that tree is the London tree par excellence; but in Battersea Park grow trees that flower more freely there than elsewhere; and the catalpa in that lovely park, as in Gray's Inn Gardens, grows exceptionally well and blossoms well. It is surprising how rarely it is found in country-house gardens.