Pleaching - the word comes from an old French term meaning "to braid" or "interweave" - is a technique is which grafting, plant training, pruning, hedging and topiary come together to allow gardeners to weave with live trees.
The best trees for pleaching are Limes (Tilia) hornbeam, willow, whitethorn and laburnum.
For pleaching hedges, trees are planted about two metres apart in a line and allowed to grow until they are firmly established. Cut the tops off all at the same height. This height is about the height you want the hedge to be. Make a connecting frame of wires along which new growth can be trained until the branches interweave. (It will take a few years). Remove all shoots that grow out of line. Create all sorts of effects from a thick hedge raised on stilts to a green tunnel.
Another form of pleaching is to tie the shoots to a frame like a window, circle, heart and alien they reach the top of the frame graft them together into a single stem. The frames can be removed after a few years leaving the shaped gaps in the trees.
A third form is using single trees and weaving them in to strangely shaped objects.
The fashion of pleaching goes back to 17th Century. Lime trees were planted in rows quite close together and when they were sturdy in the ground they were topped to encourage side branches to grow. Frames and wires were used to train and weave branches into hedges, arches or tunnels. The intertwining of branches eventually grafted themselves together and as they grow each year become further entwined. Gradually the growing flowing shapes took places.
There are some copies of famous pleached features appearing in NZ eg Pleached hedge at Lincoln University and Laburnum tunnel at Larnach Castle in Dunedin.
Pleaching is a time consuming but rewarding garden art form. It is time consuming in the amount of work required to prepare and train young shoots and also in the number of years until a shape is formed and is at its best.
By Alan Jolliffe