TAKING THEIR LEAF

Photo caption: Crowns of ancient pedunculate oaks Quercus robur in their autumnal livery.

At this time of year the foliage of deciduous trees and most non-woody plants is taking its leave, preparing for winter dormancy and then the coming spring. In this annual shedding and shrivelling, though, we are presented with a stunning show of colour as our greenspaces turn to red, yellow, rich brown and gleaming gold in the low-angle sunshine of the year’s last weeks. The famous line by Albert Camus L'automne est un deuxième printemps où chaque feuille est une fleur is an apt description of a phenomenon that moves so many of us.

Of course, there is no teleological intent in this process: it is a function of the evolutionary fitness for best survival of these plants during times of cold and dark when successful growth, sex and reproduction are impractical or impossible for much vegetation at our latitude. Foliage contains nutrients, nitrogen, phosphorus and potassium particularly, that many plants can retrieve and usefully store in their roots, woody tissues, bulbs or whatever. In deciduous trees and other woody dicotyledons, abscission (the separation of leaf from twig) occurs after those nutrients that can be withdrawn have been resorbed and when chlorophyll production ceases.

The beautiful colours are also revealed a little before abscission once the chlorophyll-enabled photosynthesis stops and the other pigments, masked by chlorophyll’s green, are able to show themselves. Carotenes produce the yellows and oranges whilst anthocyanins show shades of red and purple. Russets and browns depend on the mix of the pigments which vary between species. Several other factors such as temperature and humidity also affect the range and intensity of colours. Here are a few examples of beautiful leaves I photographed last week before all the rain.

From top left: field maple Acer campestre, aspen Populus tremula, hawthorn Crataegus monogyna, an ornamental maple, a Viburnum variety and sweetgum Liquidambar styraciflua.

Betts Ecology’s open spaces contain brilliant autumn colours. Whilst we may not be able to compete with the amazing vast tapestry of fall colours of Canada and the USA, you can still find plenty to admire in our open spaces. Do get out there and look. Searching out not only native trees and shrubs but also some of the ornamental plantings can reveal an exciting palette of colours and leaf shapes.

  © Betts Ecology