Originally published December 2010
Hello Everyone! As we once more enjoy the build up to the Festive Season the woodland denizens, perhaps with last Winter in mind, are feeding for England. Every last visible seed, berry, nut and unfortunate insect and earthworm is being snapped up by the birds and animals as they pile on their life-saving fat layers. Autumn splendour is rapidly becoming n’but a memory and very soon the ever-green plants will be standing alone, fully clad and silently triumphant after their seasonal battle of attrition with their gaudily-coloured rivals.
Why we get this annual swan song of the deciduous trees is down to a number of factors, but ultimately (as is everything else in life!) due to changes in biochemistry. Those of you who were inspired by my article on Building with Light and went on to study the complexities of botanical science (hands up!) will know that the green chlorophyl is not the only chemical found in leaves; indeed there are a myriad of colours lurking in each of those busy plant cells just waiting for the season to change and photosynthesis to grind to a halt. The decrease in the number of hours of sunlight or photoperiod (no Greek translation needed there!) acts as a trigger for the trees to litterally cut off the fluid supply to the leaves. This process known as abscission (from the Latin scissio – cleaving) starts with a thin layer of cork-like cells forming at the base of the leaf and restricting the flow of sap. By now the younglings will be waving their arms in the air with a smug air of realisation of how it all works. So, in order that the adults catch up, here, once again, is the chemical equation for photosynthesis…
With two of the three elements (water and sunlight) decreased, photosynthesis ceases and that powerhouse of energy production, the chlorophyl molecule, simply breaks down. The other chemicals present in the leaf deteriorate at a slower rate than the mighty green, thus giving us our autumnal arborial display of pyrotechnic-like finery. Just as chlorophyl absorbs red and blue light and appears green, so does carotene absorb blue-green and blue light and reflects yellow light back for us to enjoy. In similar vein anthocyanins are the basis for the colour red, xanthophylls, yellow-orange and tannin, brown or tan.
At this point children and adults alike will be leaping up and down vociferously protesting that there is a flaw in all of this. Why are evergreen plants ever-green if photosynthesis has ceased for the season? The answer is found in another of Ma Nature’s little quirks; which as we have come to appreciate is wholly keeping in character! Evergreen plants have adapted to live beyond the range of their fair-weather relatives. Lower nutrient levels, higher acidic levels and stress through drought are dealt with with consumate ease. A cunning combination of leaf shape, as in the pine needle, and thick waxy cuticles, such as the holly leaf, keep water loss to a minimum. Feel the glossy surface of an Ivy leaf (carefully) and it becomes clear how it thrives, seemingly at the expense of other plants. That is a little unfair as it is just a case of the familiar scourge of the garden having evolved perfectly for the job in hand!
This takes us nicely into the second theme of this month’s ramblings. The gardeners’ bane it might be throughout the year but come Christmas we are all singing about Ivy in jolly, mulled wine-fuelled carols and gathering armfulls of the stuff to intertwine the boughs of holly decking our halls. Most people are familiar with the concept that pagans both decorated evergreen plants at this time of year and brought them inside as a symbol of life continuing throughout the dark Winter months. The Great Sandal’d and Toga’d Ones had a whole week of celebration in honour of Saturn. In true roman style food and drink were key features throughout the jollifications, plants were adorned and even slaves were given a modicum of freedom; though again in true roman style, not enough to upset the natural order of things! Mistletoe, the Druidic symbol of fertility, is commonly brought into the house over the festive period however this practice is rarely mentioned before the 18th century. These days Christmas would not be the same without at least a reference to that old partnership, the Holly and the Ivy. Unlike the Christmas tree which only became popular in Britain when Queen Victoria married her german cousin, these two evergreens have been associated with the Season, and with each other, for centuries. Old carols hail these plants as the ultimate symbols of survival. Henry VIII, in a startling moment of ecological clarity, composed Green Groweth the Holly, a song comparing the enduring nature of the plants to his own love of his lady; or should that have been contrasting!
So there it is; the last article of 2010 incorporating some biochemistry, Winter hardiness, Royal traditions and of course the Romans. Enjoy some seasonal walks in our little Reserve making sure you pay homage to the woodland evergreens.
As the holly groweth green
And never changeth hue,
So I am, and ever hath been,
Unto my lady true.
Green groweth the holly, so doth the ivy.
Though winter blasts blow never so high,
Green groweth the holly.
As the holly groweth green,
With ivy all alone,
When flowerys cannot be seen
And green-wood leaves be gone.
Henry VIII Tudor (1491-1547)
Happy Christmas One and All!