At 8:30 on a dark, chilly evening in February, Anna Leggatt took me on a tour of her rock garden. Gently lifting a protective evergreen bough, she showed me the sleeping buds of Helleborous niger, the deep green leaves of Daphne arbuscula, and the whirled branches of Chaemaecypyaris obtusa nana. Pointing to the bones of her latest project, she explained how only frozen ground stopped her from completing the new crevice garden late last fall.
Anna is a rock gardener. She believes that anyone can make an interesting rock garden with, "a boulder and a little Japanese maple, gritty soil, and two or three little rock garden plants." Anna shares her experiences and expertise to show GardenMart readers how to build a rock garden.
Start with the perfect site "Ideally, you have a slope that faces southeast," says Anna. Although some rock garden plants do very well facing north, Anna discourages gardeners from building a south or west-facing garden because of the drying effects of the hot afternoon sun. But it seems that rock gardening rules are not cast in stone. Anna adds that it is okay to build a west-facing garden if it's lightly shaded by trees far enough away that dripping branches, falling leaves and hungry roots don't invade the garden.
"Alpine plants, strictly speaking, are plants that are growing high up. They're used to ultra violet light; they're used to rapid drainage; they're used to extremes of temperature; they're used to strong sun. What they don't like is damp." A southeast facing slope sited away from trees provides the right kind of sun and the rapid drainage on which these plants thrive.
Anna suggests that gardeners without a natural slope on their property build a rounded pyramid-shaped raised bed with sides facing southeast and north with a shaded western exposure. The different exposures on each side of the raised bed allow you to experiment with a wide range of plants -- primulas that love northern light, Mediterranean plants that soak up the sun, and tiny campanulas that like to shelter from the winds.
Soil -- the true grit The perfect soil for alpine plants is one that retains moisture but drains well. "Now, that sound a bit contradictory", says Anna, but she goes on to explain that the soil must trap enough moisture for plants to survive while allowing the excess to drain away.