Last January Alan Titchmarsh wrote a column for the Express advocating the benefits of washing the trunks of silver birch trees to make them a bright feature of a garden. He is not the first person to suggest washing trees, but it has been suggested before for a very different reason: to make trees grow faster.
The following ‘snippet’ has been ‘snipped’ from The Repertory of Arts and Manufacturies, Volume 9 from 1798, quoting from the Philosophical Transactions of the Royal Society of London.
I had for several years intended to put in practice the celebrated Dr. Hales’s advice of washing, with that of Mr. Evelyn of rubbing, the stem of a tree, in order to increase its growth; but other avocations prevented me till the last spring, when, as soon as the buds began to swell, I washed my tree (a beech) round, from the ground to the beginning of the head, viz. between thirteen and fourteen feet in height. This was first done with water and a stiff shoe-brush, until the tree was quite cleared of the moss and dirt, then I only washed it with a coarse flannel. I repeated the washing three, four or five times a week, during all the dry time of the spring, and the forepart of the summer; but after the rains were frequent I very seldom washed. The unwashed tree, whose growth I proposed to compare with it, was, (at five feet from the ground,) before the last year’s increase, three feet, seven inches nine tenths; and in the autumn, after the year’s growth was completed, three feet, nine inches one tenth; viz. increase one inch two tenths. The washed tree was last spring three feet, seven inches two tenths, and in the autumn it was three feet, nine inches seven tenths; viz. increase two inches five tenths; that is, one tenth of an inch more than double the increase of the unwashed tree.
The writer goes on to describe further experiments with multiple trees at great length. He concludes that there is potential for financial gain from washing trees, as ‘six years will produce above five cubic feet of timber, as the oak is eight feet round, and above twenty feet long, and sixpence will pay for the washing; consequently, there remains nine shillings and sixpence clear gain, in six years.’
Funnily enough, not once did the thought occur to the writer that ‘washing’ the trees also involved watering them.