This north facing retaining wall was built in 1986 with the idea of growing rock-loving plants in the sharply drained crevices. The stones were laid up and shimmed in the traditional manner, but the spaces between the stones were then filled with sandy loam. This allows the plants to extend their root-run into the moist earth behind the wall. The north-facing vertical aspect affords sharp drainage for the crowns of the plants and is a haven for plants that require bright light but would suffer on a hot south facing wall.
After twenty years, many of the original Saxifraga, Campanula and Androsace have continued to thrive and many other pants have seeded and spored into the crevices. These include a few pleasant surprises such as Athyrium niponicum var. pictum, Polystichum braunii and Adiantum pedatum.