The technique of growing some shrubs and even trees horizontally on a wall, started I believe in the 17th century in Europe and came to be known as the espalier method. By training juvenile branches on a wall when they are flexible, and by making sure the branches are parallel to the ground, the pushing forward of the leading bud, known as apical dominance is abolished, and the once dormant lateral buds burst into life. Originally developed as a way of increasing fruit production in a limited space, espaliering can be used to significantly increase the quantity of flowers that flowering shrubs can produce.

Virtually any woody plant, tree or shrub, can be adapted to growing in an espaliered form. However it makes sense to take advantage of the particular pattern of growth caused by the horizontal training of branches, to use flowering species, or those that produce either edible or decorative fruit. Excellent examples of this are climbing roses -- try the Bordeaux flowers of "Don Juan" on a whitish wall, Pyracantha, or Bougainvillea, while some species can also be trained to make formal patterns, such as pear and apple trees. Another benefit is that shrubs grown as espaliers to cover a wire fence, take up less width than if grown freely or even as sheared hedges, an important feature when space is limited.

Where water is at a premium, it is necessary to reduce the space allotted to herbaceous flowers in the garden. As an alternative, a composition of say pebbles on the ground plane, dotted with a few sculptural plants, and the wall of a building draped in the flower color of an espaliered citrus tree, can be really spectacular, and far more creative than the standard annual flower bed. As far as water consumption is concerned, there is a massive difference between irrigating a tree or a few shrubs, compares to hundreds of annual plants.

So I think that growing espaliers on walls or fences should become an integral part of the dry climate and Mediterranean gardener's repertoire. The espalier technique is though somewhat labor intensive. It requires the setting up of a frame which can take the weight of the plants, and involves a considerable amount of training and pruning over the gardening year. Nonetheless it is well worth the effort and can really help to make your garden special.