LIVING STRUCTURES

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(See also Living Fences)

"Walking in a thick pleached alley in mine orchard" - William Shakespeare, 'Much Ado About Nothing'

PLEACHING

A plant is considered to be 'inosculate' 1 if it is self-grafting; if the branch of one individual will, as the result of gentle abrasion, form a living bond with the branch of another individual, or with another branch of the same plant. When this grafting is aided or initiated by humans, the process is called 'pleaching' 2.

In mediaeval Europe, in areas where annual flooding endangered human settlements, the pleaching of inosculate trees was employed as a solution to what otherwise might have been an insoluble problem. The trees were planted on a grid, like a small orchard. As they grew, branches were pruned and trained along this grid, so that eventually the branch of one tree met that of its neighbour. At that point, an incision was made in the bark of both branches and they were tied together, like blood brothers or sisters. The analogy is deserved in that not only did these branches grow together to form one member, but their support activites (condition of water/minerals and sap) merged, thereby joining the life processes of the neighbouring trees.

When these pleached branches had matured to form substantial limbs, connecting all the trees of the 'orchard', planks were thrown across on which huts were erected, eight or ten feet above the seasonal flooding level. Dense foliage grew out from the marginal trees, while those on the interior continued to draw water and minerals from the soil for the use of the collective, and also receiving sustenance from same. And of course the exterior foliage served to shelter the huts from climatic excess, and perhaps to bear edible fruit.

Now, since the growth of these inosculate trees was planned, regulated and protected by humans to serve a human need and since the trees did presumably thrive, we can conclude that a state of interspecies cooperation, if not symbiosis, was achieved. And though it lacked the sophistication of the Archetypal Plant Gall 3, it was still a start; we could picture further developments, say the introduction of vines or second storey growth, that woud one day lead to the redundancy of the built hut for the provision of total shelter.

Sadly, architectural pleaching represented a false start in the evolution of human technology. The inexorable trend was isolationist, favouring the built over the grown environment. Though pleaching survived as an ornamental garden art, it in no way compared to its structural predecessor.

But the revival of architectural pleaching can be seen as a positive step toward living in the natural world. The very fact that it demands a commitment to both time and place attests to its merits as an alternative trend in human environments. And pleaching can be undertaken without denying our present dependence on mechanical living systems. We still have access, privately or collectively, to some outdoor space. And though our knowledge of what to plant and how to grow it is lacking as imaginations are blunted, there is reason to hope. For in summer, sleeping beneath pleached arbours that grow as noticeably as themselves, our children will surely glimpse broader possibilities.

Pleaching and Espalier

Pleaching is incorporated within the French espalier 4 system of orcharding. Trees no taller than 2 metres are trained to conform to primarily two-dimensional shapes, and thus allow for closer planting, earlier fruit production and easier harvesting. The system is well suited to walls, fences and walkways and often incoporates the use of horizontal wires along which the laterals (branches growing off the side of the the trunk) are trained.

Branches are bent rather than cut. Where limbs touch, they join, giving strength to the tree. Where limbs are growing too slowly, they are bent upward; where too fast, they are bent downward, slowing vegetation growth and increasing fruit spur growth.

Trickle irrigation can be run along the bottom wires clear of mowers, etc. Hedgerows of coloured varieties should run north­south for even colouring, while green varieties should run east­west to prolong the harvesting period.

1. Osculate:­ To kiss; to bring into close contact or union. In Geometry, to touch so as to have three or more points in common at the point of contact. From the Latin 'osculum', little mouth, kiss. ­ Macquarie Dictionary [Note that the adjectives 'osculate' and 'inosculate' mean much the same thing ­ ed.]

2. Pleach:­ To interweave growing branches, vines, etc, as for a hedge or arbour. The word 'plexus' derives from the same Latin root word 'plecto', meaning to weave or twist together. ­ Macquarie Dictionary / Websters New Encyclopedic Dictionary

3. Gall:­ In humans, gall is associated with bitterness and bile ­ which can have an irritant effect upon the constitution ­ resulting in gallstones, etc. In the vegetable kingdom, a gall is scarlike vegetal growth on a plant caused by the irritant action of insects, nematodes, fungi, bacteria, viruses, chemicals, and mechanical injuries. The response of two plants to the mechanical (irritant) action of each of their branches rubbing together through wind action, etc, can be to form galls around the wounded areas ­ and by default to create a natural pleach.

4. Espalier:­ Trellis or framework on which fruit trees, vines or shrubs are trained to grow flat. (From the Italian 'spaliera', to support, and 'spalia', shoulder.) ­ Macquarie Dictionary

This is one of the specimens from a unique pleached forest in Scotts Valley, California. The copse has been described as a 'tree circus', the creation of Axel Erlandson, an industrious but impoverished Californian farmer. Axel had noticed how two Sycamore trees had 'rubbed together when the wind blew, exposing the green cambial layers beneath the bark'. They had fused invisibly as the seasons passed. Axel decided to reproduce this effect himself. Using living trees, Ash, Birch, Elder, Alder, Oak, Sycamore, Poplar and Plane, he formed hearts, hoops, loops, diamonds, circles, squares, corkscrews, rectangles, onforms and rhombohedrons. Of the 67 trees trained by Axel before his death in 1964 at the age of 79, only 52 remain. The trees have become a threatened remnant of an ancient horticultural technique mentioned by Shakespeare in Much Ado About Nothing, Act I, Scene II, when Antonio speaks of 'walking in a thick-pleached alley in mine archard'.