Storm Doris brings Cladoptosis to our trees: what is it?
With Storm Doris bringing wind gusts of 94 mph, the botanical word of today has to be... Cladoptosis!
You might not have heard of this term before, but you’ll be very familiar with its effects. Venture outside this morning and as you step over and around the scattering of fallen twigs and small branches that litter the pavement, maybe cursing as you do, you’re seeing cladoptosis in action.
The term comes from the Greek clados, meaning a branch, and ptosis, meaning falling (the ‘p’ in cladoptosis is sometimes silent, but sometimes not. I tend to take after our university lecturer who did pronounce it).
The word describes the process of self-pruning in trees as they grow. Just as unwanted leaves are shed in autumn, so are any unwanted small twigs and branches. If this didn’t happen, tree crowns would become hopelessly crowded and congested, with too many leaves to support and too much shade being cast on lower branches. It’s all part of the way that trees grow – opportunistically producing lots of smaller shoots and branches that can fill the spaces around them if need be. As trees grow over time, their canopies bump into neighbouring trees; in the resulting jostling for space this extra ‘shoot’ capacity is shed when it’s no longer needed. In addition, cladoptosis also allows any damaged and diseased branches to be dropped from the tree.
The process itself is similar to that of leaves when they’re shed in autumn, with a small disk of tissue – the abscission layer – developing at the base of the leaf stalk or twig. When this tissue dies and gives way, a clean scar is left behind which helps to prevent infections.
Cladoptosis can occur at any time of year but in Britain it’s most visible in autumn as gales sweep in and help the process along. When you see all those small twigs and branches lying on the ground, don’t think of them as having just ‘fallen off’. Most of them will actually have been shed on purpose, part of a carefully orchestrated pattern of growth being played out by the trees above your head.
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