Rock gardens display alpine plants in an environment that resembles their native habitat; a crevice garden is one of the most visually appealing and structurally authentic rock garden designs. With the appearance of more rock than soil, a crevice garden is typically a mound of soil that's faced in stone, which gives the impression of several large rocks on a mountainous terrain that have eroded and cracked over the ages-providing pockets and fissures where plants can grow.
A crevice garden can be as small as a corner planted with half a dozen specimens, or as large as a major feature with pathways that twist and climb through rock formations, revealing delightful splashes of colour tucked into nooks and crannies. Gently sloping, small-scale crevice gardens can successfully be built by novice landscapers and integrated into entranceways, courtyards or garden beds. If building by hand, a three- by three-metre structure is manageable for the average gardener; mechanical equipment is probably required to lift and move the stones for anything larger.
Harvey Wrightman, of Wrightman Alpines near Kerwood, Ontario, offers workshops on how to build crevice gardens based on a design by Czech botanist Josef Halda. Last May we asked if we could tag along at a four-hour demonstration, where we witnessed rookie and veteran landscapers transform half a dozen piles of soil and rocks into structured, ornamental garden features.
PLANNING AND DESIGN
“The planning stage is the most difficult but most important part,” says Harvey. “You can't just throw stones on a pile of soil. You need a concept of what the final structure will look like.”
A crevice garden has two distinct sides: a gradual flagstone-like side, called the dominant side, where stones are laid on the surface of the mound five or so centimetres apart (a few at the ends are placed 10 to 15 centimetres apart). The top and bottom edges are abutted together-this is what holds the stones in place-and you're left with vertical crevices.
On the other side, which is steeper, stones are stacked similar to building a dry stone wall, but down a slope; two-thirds of each stone is dug into the mound. The effect on this side is an exposed, step-like ledge, and you're left with mostly horizontal crevices in between layers of rock.
The height at the garden's peak should be a minimum of 60 centimetres; the slopes on both sides, between 20° and 45°. Your crevice garden can be as small or as large as you like, but keep stones and plant material to scale.