This is the month when the autumn colours of the trees are most spectacular. As the day length and temperature decrease, the production of chlorophyll (the green pigment which traps sunlight for photosynthesis) slows and stops, so that other pigments in the leaf, previously hidden by the chlorophyll cause the leaf colour to change. This is most noticeable in trees. If carotenoid pigments become the most important in the leaf, its colour will turn yellow, while leaves containing mainly anthocyanin pigments appear red. In leaves where the amounts of both these pigments is low, tannins may be responsible for brown leaf colour as seen in some oaks. During late summer and autumn a layer of cells is laid down at the base of the leaf stalk which allows leaf fall without infection to the tree.
Following damp weather, look for mushrooms and toadstools on the woodland floor; some are very well camouflaged amongst the dead leaves.
If you are interested in finding out more about fungi look for Fungal Forays in Bromley's Walks, Talks & Events leaflets obtainable from libraries or High Elms Country Park.
Twining around the hedgerows and scrub on chalky soil look for Traveller's Joy this month with its plumed seeds giving it the appearance for which it is also named 'Old Man's Beard'. This plant scrambles towards the sunlight using its leaf-stalks (petioles) to anchor it. Darwin studied this and reported,
"I have seen many proofs that the petioles are excited to movement by very slight pressure. For instance, I have found them embracing thin withered blades of grass, the soft young leaves of a maple and the flowers of quaking grass. The latter about as thick as the hair of a man’s beard, but they were completely surrounded and clasped......Those (petioles) of almost all the old leaves, even when unattached to an object, are much convoluted; but this is owing to their having come, whilst young, into contact during several hours with some object subsequently removed......there was no permanent bending of petioles without the stimulus of contact. In winter, the blades of the leaves drop off; but the petioles...remain attached to the branches, sometimes during two seasons"...From Darwin, C. (1875) 'The Movements and Habits of Climbing Plants' This can be read on John van Whye’s website, 'The Writings of Charles Darwin on the Web'.
There are about 350 species of cranefly in the UK. The species below left, known as daddy-long-legs is one of the most commonly seen. Like all flies, the adults have one pair of membranous wings, the second pair which look like drumsticks, help it to balance. As September gives way to October, the remaining adults which emerged from pupae in August and September, mate, lay eggs in the soil and die. The young, known as leatherjackets because of their thick skins, hatch 10-14 days later and feed on plant roots except during very cold weather.
Acorns ripen and turn brown this month. Look for different types. Jays collect ripe acorns, which they bury individually at the woodland edge or in grassland, without damaging them, unlike grey squirrels which often chew out the embryo from the nut, preventing it from germinating. Tests have shown that jays retrieve the acorns by remembering where they buried them rather than by smell and because they usually only eat the 1st 'seed leaves', the young oak tree continues to grow. This benefits the oak because oak seedlings need open areas to thrive, and shows how woodland is a thriving dynamic habitat whose edge naturally moves. Like Darwin’s observations of hedgerows (see WHS Hedgerows page) this demonstrates how important the relationships between animals and plants often are.
Ripening fruit and nuts provide food high in calories for small mammals. Although mice and voles don’t hibernate during the winter, they eat well during the autumn, putting on a layer of insulating fat which protects them from cold weather as well as acting as a foodstore. They also hide away nuts to eat when there is less food available.
Siskins and Redpolls
As the days shorten, small mixed flocks of siskins and redpolls may be seen feeding on the seeds of silver birch trees on Keston Common. Like the finches of the Galapagos which Darwin studied, their bills are well adapted to their food sources. Siskins have slightly smaller bills than redpolls and seem to be particularly attracted to red-coloured bird feeders containing peanuts, seeds and fat.