Certain shrubs, while not actual climbers, can be treated almost as if
they were by growing them against fences, walls and trellises. Use the
same pruning methods as for freestanding plants, but tie in stems during
the summer in order to guide growth over the surface to be covered. At
the same time, shorten any shoots that are growing away from the wall to
make sure the shrub stays neat and narrow.
Pyracantha, cotoneaster, and ceanothus make excellent wall shrubs; all flower in spring at the base of stems made the previous year. Make sure that the wall is in good condition before fixing a trellis to it, as any repairs will be difficult once the plant is established. When pruning, take care not to cut back too hard into the old wood if you want blooms and berries. Shorten all new sideshoots in midsummer, leaving two to three leaves to encourage flower formation the following year, and to make any berries more visible.