seasons

'It all begins, in temperate climes, with the shortening of Apollo's journey and the enfeebling of his rays. As daylength shortens and temperatures fall, the profits of photosynthesis drop below the running costs of the leaf; it's time for 'downsizing'. Foliage represents a considerable investment of materials but, as all gardeners know, leaf mould takes much longer to prepare than ordinary compost and is a rather poor source of plant nutrients, so where does that 'investment' go? The answer is, back into the plant. Leaves are, unlike employees, not simply discarded but, rather, decommissioned. This is done so systematically and so efficiently that a fallen leaf is little more than a husk, but it is this decommissioning process which also gives us our glowing Virginia creepers, mountain ashes, beeches, birches, spindle trees, acers, and all the rest. These glorious autumn colours are, in fact, a 'fast rewind' of the three billion years of plant evolution in a few short weeks.
Traditionally we folk of temperate latitudes associate autumn, in a wistful, pre-Raphaelite way, with plant death, but even a cursory glance at a deciduous tree at this season presents another of those paradoxes. An infallible sign of the incipient demise of a plant is the wilting of its leaves, but a majority of autumn leaves remain stubbornly turgid right up to and often beyond the moment of fall: how else would we be able to appreciate those banks of autumn colour in mixed woodland? Autumn leaves are very much alive but are undergoing an active and controlled senescence, a senescence which Philippe Matile calls 'the most conspicuous example of phytogerontological events'. Before the leaves finally fall there is an enormous reabsorption of protein, as much as 60 per cent in some cases, along with essential elements such as potassium, phosphorus, sulphur, iron, manganese and magnesium, this latter being a key component of chlorophyll itself, while iron and manganese are essential members of the photosynthetic corps de ballet.'
james | hortus | autumn | leaves | seasons