There has been a recent announcement by the Forestry Commission, to whom it has become apparent that, despite its designation as one of the strangest years of weather on record, 2012 had also produced one of the most varied colour schemes in our autumn foliage.
In the wake of the miserable summer we’ve suffered it would seem implausible that our autumn palette could adopt such vibrancy – after all, hot and dry summer months have become synonymous in horticultural circles with colourful autumns. However the colouration of foliage, particularly in the transition to winter, is not an exact science and the Commission has a theory as to what might have caused this welcome surprise.
To understand the underlying causes of autumn vigour, it is necessary to look at the science behind it, which is actually a lot simpler than you might think. Sunlight encourages the production of chlorophyll in the cells of plants and more specifically their foliage – giving the distinctive green tint that we associate with them. Therefore, in the lead up to winter, as the days shorten and sunny weather becomes more sparse, less and less chlorophyll is being produced, thus allowing the true yellow colour of the leaves to show through.
However, it is precisely this decline that triggers the most vivid displays. In the absence of chlorophyll, certain sugars and particularly one called Anthocyanin, are able to flourish and it is this that tints the leaves a distinctive autumn red or purple. It is believed that the brief spate of sunlight we enjoyed in September leant a final boost of encouragement to our native woodlands and that the early frost that succeeded it helped to lock in those colours as they were established.
Several native and imported species are famed for their autumn plumage and among these are the
Japanese Maple, Acer palmatum ‘Osakazuki’,
a medium-sized shrub for acid soils,
another acid-loving shrub with a long flowering display in spring
which, unusually for autumn colour shrubs, is actually evergreen,
which can be grown as a tree or large shrub and is tolerant of most soils,
Katsura, or Cercidiphyllum japonicum,
a lovely Japanese variety, known more commonly as the Candy Floss Tree, a name derived from the sweet smell it releases as the aforementioned sugars are broken down, and thus certainly worth consideration for your winter garden.
By Josh Ellison