| The Heath and Hampstead Society’s third Kate
Springett lecture was given on 17th Sept 1998. The talk on "The Wild Flowers of
London" drew a large audience and was very well received. This is a brief summary of
the talk.
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| London provides a home for a remarkably varied flora which, in terms of its sheer diversity, is unequalled in any comparable area of the British Isles. In 1983 the London Natural History Society published a "Flora of the London Area" which gives a historical and geographical account of the flowering plants and ferns found wild within 20 miles of St. Paul’s Cathedral based on records collected by the Society from 1965 to 1976. A total of 2055 different kinds of wild plant were recorded. This figure far exceeds those found during comparable studies of the floras of surrounding counties. How has this come about? There are, I believe, three major features of London which have contributed towards its botanical diversity: | |||
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| The heat island effect In common with other large cities, the central, built-up part of London experiences higher temperatures than the more peripheral areas and the countryside round about. This is accounted for by the presence of buildings and streets with their reflective surfaces, and the abundance of domestic and industrial heat sources. As a result, the central area of London has a reduced number of frosty nights, a longer growing season and higher maximum temperatures in the summer. This brings the urban climate closer to that of the Mediterranean, allowing plants such as Oxford Ragwort (Senecio squalidus), London Rocket (Sisymbrium irio), Chinese Mugwort (Artemisia verlotiorum), Guernsey Fleabane (Conyza sumatrensis), and many other warmth-demanding species to flourish. |
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| On Hampstead Heath the "heat island effect" is less
pronounced than in the surrounding built-up area, but Guernsey Fleabane (first recorded in
London in 1984) has recently become well established around the fringes of the Heath and
Oxford Ragwort has long been a feature of its old walls. The latter plant is a native of
southern Italy and Sicily in particular (where it grows on the arid soils derived from the
volcanic ash of Mt. Etna). It was an early introduction to the Oxford Botanic Garden, from
which it escaped at the end of the 18th. century by means of its light wind dispersed
seeds. A hundred years later it had reached London by spreading along the railway system,
finding the well drained clinker of the tracksides much to its liking and a reminder of
its native habitat.
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| Horticultural Influences | |||
| The British are often characterised as a ‘nation of gardeners’ and nowhere is this more apparent than in London, where the number and variety of gardens is a striking feature. Many wild London plants derive from such gardens, either as a result of seed dispersal (Buddleja, Michaelmas Daisies, Cotoneasters, Antirrhinums, etc.) or as "cast-outs" of more vegetatively aggressive species (Japanese Knotweed, Ground-elder, Golden-rod, Snowberry, etc.). Occasionally such garden-derived species form hybrids with their native relatives, and London supports a number of these unusual plants. One example is the Highclere Holly (Ilex x altaclerensis), which is now a feature of many London woods including Ken Wood. | |||
| This plant has arisen through hybridisation between our native Holly (Ilex aquifolium) and a South American species (I. perado). The common Bluebell in London is also a hybrid, derived from the native species (Hyacinthoides non-scripta) and the Spanish Bluebell (H. hispanica)These hybrids are fully fertile with their parents and ‘hybrid swarms’ result, with plants showing a wide range of intermediate characters. On Hampstead Heath, the native Bluebell is still widespread, but is largely supplanted by hybrids around the edges of the Heath and close to houses. Occasionally hybrids arise in the wild between two closely related plants of garden origin whose normal geographical distribution keeps them apart. |  |
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| The "Haringey Knotweed" is one such plant, having as its parents the Japanese Knotweed (Fallopia japonica) and the Russian Vine (F. baldschuanica). It has been found at only one site in Britain, at a Local Nature Reserve called Railway Fields in Haringey. This is a remarkably "well behaved" plant showing little of the aggression of its two notorious parents. It attempts, rather feebly, to climb like its father (the Russian Vine) during the summer, but falls flat on its face every autumn when the first frost arrives, as it has inherited the herbaceous growth pattern of its mother (the Japanese Knotweed). | |||
| Relict Habitats The fringes of London contain occasional pockets of vegetation that have escaped agricultural "improvement", and some of these support nationally rare native plants. In the London Borough of Ealing, for example, there is a thriving population of the Narrow-leaved Water-dropwort (Oenanthe silaifolia), a plant of unimproved damp meadows which has become increasingly scarce in the wider countryside where such habitats have disappeared through drainage and agricultural intensification. A population of Water Avens (Geum rivale) was recently re-discovered in a water meadow close to Heathrow. This beautiful plant has disappeared from many of its former sites in southern England and the Heathrow colony is now thought to be the most south-easterly remaining in Britain. It is directly threatened by the proposed new Terminal 5 development. Closer to home, in Tottenham, the nationally scarce Wall Bedstraw, (Galium parisiense), miraculously survives on a wall , not far from where it was first recorded by John Sherard in l690! |
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On Hampstead Heath, there is now no surviving heathland worthy of the name and, although a number its more characteristic plants have recently been successfully re-introduced, the heathland habitat itself is likely to prove much more difficult to restore. Ancient woodland, on the other hand, continues to flourish at Ken Wood where the native Bluebells and Wood Anemones were first noted by the apothecary Thomas Johnson during a visit on May 1st 1629. |  |
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Later in that same year he recorded Mountain Ash, Hornbeam, Alder Buckthorn and Wild Service among many other species which still thrive in the Wood today. His published records of these plants and of the many others that he saw growing on the adjacent Heath can be regarded as the first British Local Flora. Much botanical recording has been carried out on the Heath since Johnson’s time, making its flora one of the best documented in the world over a period of more than three hundred and fifty years. The London Natural History Society are following this long tradition and are currently co-ordinating a new survey of the Heath whose changing flora continues to surprise and delight. | ||
