Tree love blossoms
While walking in the New Forest in southern England, my wife and I came across two trees that appeared to be holding hands. They actually had a branch linking their trunks. How and why did this happen? A hopeless romantic I may be, but even I don鈥檛 think it鈥檚 because the trees are in love.
鈥� The twinned trees are not unique. There is a similar but more advanced twinned tree near Strachan in Aberdeenshire (see photo, top left) at approximate UK grid reference NO637927. A friend who has observed the trees growing for many years tells me that the recipient tree used to be much the smaller of the two, but its growth has now outstripped that of the donor tree.
Maureen Young
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Aberdeen, UK
鈥� The phenomenon is called inosculation. It is not uncommon between trees of the same species but much rarer between different species. It seems to be most common when a branch or trunk interpenetrates another within the same tree. Two branches rub together, removing some of the bark, and then a natural graft forms and the two trees grow together. I have seen a single branch joined to two or three others in an overgrown coppice.
Trees and shrubs that will readily inosculate include elm, holm oak, olive, live oak, golden oak, pear, apple, peach, almond, beech, hornbeam, linden, hazelnut, crepe maple, dogwood, golden willow, wisteria, grape, privet, laburnum and sycamore.
When inosculation is created by human intervention it is called pleaching, and is commonly used to form an avenue of trees all joined together (see ).
Other examples include the 鈥渢ree circus鈥� (top middle) created by American Axel Erlandson which opened in Scotts Valley, California, in 1947 (), while American artist Dan Ladd creates what he calls living sculptures using pleaching (). Pleaching can even be used to construct living buildings (top right):
Nick Kotarski
East Bergholt, Suffolk, UK
鈥� Pleaching is an ancient agricultural and horticultural technique that involves weaving together branches to form walls, ceilings, arches and other ornamental structures that can, in extreme examples, actually form homes. Invented by horticulturists during Roman times, the technique is mentioned in Shakespeare鈥檚 Much Ado About Nothing and is still practised in gardens today, where it is once more gaining interest among creative landscapers. The method is well suited to walls, fences and walkways and often involves training branches to grow along the horizontal branches off the side of the main trunk.
In its purest form, pleaching involves making small cuts to encourage branches to graft to each other in a kind of forced inosculation. Trees that self-graft are, naturally, the most suitable species. These typically have pliable branches that can be directed into and through cuts in other branches to form load-bearing structures. Apple, linden, elm, hawthorn and pear trees work especially well. Branches are usually bent rather than cut. And where the limbs touch, they join, giving strength to the tree.
Mount Vernon in Virginia, former home of the first president of the United States, George Washington, has fine examples of pleaching 鈥� Ed
This week鈥檚 question
Canned heat
When my father was undergoing military service in the desert, his medical officer told him that should he ever become separated from his unit and stranded in the dunes the best course of action would be to drink his water supply 鈥� a 2-pint (1.1-litre) flask 鈥� over the first couple of hours rather than trying to eke it out for days. Is this true? Would either course of action be more likely to help him survive? And why?
Thomas Hutchinson
St Ives, Cornwall, UK