If you went for a walk along a path in a wood or beside a stream or canal, or drove down a country lane last weekend, everywhere you look you would have seen a lush growth of plants. Unfortunately a small number of plants will be dominating all others. Engulfing many verges will be cow parsley, with its tiny white blooms on umbrella-like stems, the soft leaves of the common nettle on erect wiry green stems, and thick tangled prickly brambles. And at roundabouts, you will see thousands of lovely ox-eye daisies and buttercups, but not much else.
Going back many decades I can remember a good mix of flowers alongside hedgerows and on the edges of woods, and beside paths on commons and in parks, though not being an expert on plants, I don’t know most of their names. And there were so many more butterflies: brimstones, orange tips, hairstreaks, blues, specked woods, fritillaries and many more. Cow parsley may appear to be very decorative of our roadside verges, but where are all the other plants.
The Centre for Ecology & Hydrology, which is part of the Natural Environment Research Council, carries out surveys of the countryside every ten years, and their survey in 2007 found that between 1978 and 2007, the extent of cow parsley in Britain had increased by almost 60% in the plots surveyed. That’s more than half as much again of the stuff as there was 30 years or so ago. But why is it happening?
There seem to be three reasons: how roadside verges are managed nowadays, the increased fertility of soil due to intensive farming, and the aerial deposition onto the land of compounds from car exhausts.
In the past, verges were often grazed by farm animals or were cut for hay, and the grass and other plants, once mown, were taken off. Now verges as well as hedges are mown by local councils, and the mowings are left in place, which add nutrients to the soil and makes it more fertile. The fertility of soil along hedgerows and on the margins of fields and woods is increased by the large amount of nitrogenous fertilisers used by farmers on their crops. That’s the reason why the chalk grassland of Salisbury Plain supports such a diversity of plants: it’s never been sprayed with agricultural chemicals because it is an army training ground. Significant areas of grassland have been ‘ploughed in’ since the Second World War which led to an increase of nitrogen compounds in the soil. And across the entire landscape, the air and rain is more fertile because of the nutrient effect of nitrogen oxide gases emitted by motor vehicles.