Ideally constructed to imitate a natural out-crop of stone, exposed by the erosion/weathering of soil on a bank;
Uses: Can be drawn on in design to use or deal with a bank. Can be a major feature in its own right; Provide a planting area for rock garden/alpine plants (hobby/interest); Often built in conjunction with a water feature (pools, water falls, streams); (Other ways of providing for growing alpines: raised beds, sinks and troughs, alpine houses/frames).
Ideally sloping; Sunny aspect (south) not over-hung with trees or shaded by buildings; Soil naturally light (sandy to loam); Free draining. No wet spots at the bottom of the slope (might need drainage); Free from pernicious weeds (bind weed, couch, and ground elder); Not in a wind tunnel; Ideally with irrigation water available.
Materials: Natural: Local sedimentary stone (Portland & Purbeck – limestone, Shaftesbury – sandstone (green sand)). These have lines of strata; Look natural in the area (cohesive); Cheaper to purchase and transport; (The use of Westmorland limestone pavement is ACTIVELY discouraged).
Man-Made: Cast concrete or tufa:
Rogers “Hollowrock”: Building:
Start at the bottom with lines of stone to form a line of rock with the lines of strata horizontal and running from stone to stone; Move up the bank, producing planting ledges; All stones to be bedded in well for safety; No air pockets; Ideally do some planting as you build. Hazards and Risks: Weight of stones, back injury, pinched fingers; Stones wobbling or being slippery if walked on.