Tuesday, 28 February 2017

Sticky Buds

Early March would be the time when, as children, we would gather the stout twigs of Horse Chestnut,  Aesculus hippocastanum, with their unmistakeable sticky buds, and bring them home. Placed on a sunny window ledge they would soon open up to reveal their lovely, palmately compound leaves. Of course this was long before the arrival, in 2002, of the Horse Chestnut Leaf Miner, Cameraria ohridella, the caterpillars of which now so disfigure 'Conker Trees' across Britain. (Speaking of which, I wonder whether other Aesculus species are so attacked. I have in mind the North American species, known as 'Buckeyes'. I must check.)
The resinous compound which gives the buds their sticky nature presumably affords a measure of protection from insect attack, and maybe birds too, perhaps not in Britain but probably in the tree's native home in the Balkans.
The sticky buds of Horse Chestnut, Norton Road, Daventry.
28 February, 2017
It has been known for some that this gummy coating is also put to use by honey bees. They will gather it and, blending it with saliva and honey, produce propolis. The function of this substance was long thought to be that of sealing unwanted cracks and crevices in the hive, not only keeping out draughts but preventing entry by ants or other unwanted insects. It may indeed be used by the bees for this but research has shown that it is employed in a variety of other ways, particularly as an anti-bacterial agent within the hive. Bees will use any suitable resins from, for example, birch, alder and beech  and also from conifers. Wild bees have been known  to enclose certain parts of the nest with a 'propolis envelope' and again this is assumed to prevent, or at least limit, bacterial infection. An interesting case involved the corpse of a mouse found within a hive. Obviously it was too heavy to move and the whole body had been coated with propolis.
I have avoided hesitation or repetition although perhaps I could be now accused of deviation from the subject of sticky buds, but I will return later in the spring to Horse Chestnut trees. You have been warned!

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