Fruits and foliage provide a welcome splash of autumn interest throughout the Garden.
The Sorbus, or rowans, have been full of fruit from some weeks now, and S. folgneri and S. americana are bedecked with glossy berries which pre-empt the colouring of their foliage. Many of the roses are now showing their hips, with Rosa soulieana and R. filipes 'Kiftsgate' providing a second season of interest.
While such fruits bring another dimension to the Garden, it is the autumnal colouring of foliage which brings the greatest impact. Such colouring results from chemical changes which occurs as protein and chlorophyll are returned to the tree as the leaf dies. At the same time waste products, such as silicon and chlorine, fill the leaves, and this results in a change in appearance of the leaf colour. Yellow pigments (carotenoids), which are normally hidden by the chlorophyll, become evident, while red pigments are converted to anthocyanins, and are produced by decaying sugar tissue. The impact of this change is greatly influenced by weather conditions, as warmth and bright light is now required for the remaining chlorophyll to show, while cold nights slow the decay of sugars, increasing the effect of the red pigments in the leaf.
In the Garden the effects of this chemical change are evident at every turn. The birches are taking on yellow hues, with Betula medwediewii and B. alleghanensis, the yellow birch, both putting on a good display. On the Henslow Walk, Parrotia persica, the Persian ironwood, is taking on yellow, orange, red and red-purple tints, clothing its dome of intricately woven, and self-grafting limbs. Nearby, the obovate foliage of the yellow wood, Cladrastis kentukea, are turning a clear yellow. A glance across the lake from the Woodland will reveal the orange-red palmate foliage of Acer cissifolium. Perhaps the jewel in our autumn colour crown is the Liquidambar styraciflua 'Worplesdon,' which stands sentinel beside the lake. Here the glossy, lobed leaves are changing from deep green to deep red.
With the right weather autumn colour, while changing daily, will remain with us a for several weeks to brighten even the gloomiest of autumn days.