Earth, Air, Scree and Water

Start a Scree Garden

To replicate alpine conditions, choose a sunny, airy spot. Steer clear of sites along south-facing walls or banks; alpines so situated can cook in strong afternoon sunlight. Instead, Jarvie recommends, choose a site or create a bed that slopes down to the north and/or east. If bedrock breaks through your yard, build a bed around it.

Good drainage is the single most important requirement for a successful scree garden. So along with sun and "buoyant air," you need "lean soil." Here is Jarvie's recipe: Start with a separate layer of rich compost for the bottom third of the bed. On this, spread the top two-thirds: a 1:1 mix of limestone scree (such as six-millimetre Aberfoyle grit) and coarse builder's sand. Make your bed at least 35 to 45 centimetres high (it will settle slightly). Contour gentle hummocks and hollows, but, she cautions, avoid creating a mini Matterhorn. Cover with a thin layer of scree.

As you work, consider climate, prevailing wind and eventual placement of your plants. Make small mounds on the windward side to shield any alpine that is borderline for your zone. And to protect sensitive plants, try Jarvie's trick of burying a large "antishock" rock right down inside the earth, then nestling plants around and above it. If the mercury does a quick dive, the rock radiates heat as it slowly cools (the converse is equally true), ensuring a gradual temperature change for nearby plants. Jarvie has warmed up her garden to Zone 7 in spots.

Scree gardens are not built with boulders, but Jarvie does sparingly use large one-person-size rocks (ones that are small enough for a single person to roll) and, more generously, scatterings of small pebbles to add surface variety and interest. To find rocks, ask around: some farmers sell them on a pick-your own basis. It may be tempting to raid road allowances and parks, but don't. Many municipalities have steep fines for this practice.

When choosing plants, pay attention to the colour, texture, height and growth habit (vertical, cushion or mat forming, etc.) of the foliage. Most alpines bloom only briefly and you want your bed at its best all season. Choose dependable and accessible plants to begin, then move into more expensive and exotic varieties as your experience grows with your garden. If a plant isn't successfuI in one spot, try it in another, but remember that many alpines are naturally slow-growing. Jarvie's Tsuga canadensis 'Minuta', for example, has achieved a 10-centimetre diameter over 10 years.

Gardeners who are confined to a terrace or balcony can adapt Jarvie's instructions to make small scree gardens in urns or troughs (no winter protection is needed). She notes that more than 100 members of the Manhattan chapter of the North American Rock Garden Society, one of whom came second in a mid-1990's competition, are container-only gardeners.