Scree Gardens

Dianne Westlake

The One-hour-a-year Garden

With our busy lifestyles and aging bodies, a scree garden may be a sensible alternative to the traditional, formal or cottage garden. Scree gardens are easy to make and once constructed require very little maintenance. In fact, the scree garden could be called the one-hour-a-year garden.

In nature, scree is usually found in mountainous areas. There, loose rock debris can be found at the base of steep inclines or cliffs, providing a unique growing medium. Weathered rock is broken down by the freeze-thaw cycle resulting in a mass of rocks, stones, gravel and a small about of silt. Specific nutrients are made available as a result of the chemical and physical changes brought about by the continual weathering. In addition, weather and climate extremes cause "frost heaves" or areas of disturbed soil suitable for new plant growth. This soil movement is also responsible for aeration.

In our gardens, we can attempt to recreate these conditions by building an area of gravel on which creeping plants grow, an area where we try to mimic alpine conditions. Your scree may be located on a slope, occupy a sloping gully or even a relatively flat area. If the area is level, dig a small ditch around it to help improve drainage.

As with all garden construction, planning is the key. Select a site, mark its boundaries and excavate the area to a depth of at least a foot, preferably more, especially in low ground. Stepping-stones should be installed to provide easy access without disturbing the growing medium. Ensure that these rocks are stable and partially buried. Additional rocks can be installed to add interest or to act as a focal point. An irregular rim of rock can be placed around the edge of the area with some stones being almost flush with the ground and others rising well above it

Because alpine plants require good drainage fill the area a little more than half way with broken stone, shattered bricks or a coarse gravel. This material may be piled a little higher in the spots where you wish the final constructions to be high. The next layer should be a mix consisting of one half by bulk of smaller pieces of crushed stone or gravel, one quarter grit or sand and one quarter soil, but these proportions may be varied somewhat depending upon the character of ingredients. A thorough watering at this point will prevent air pockets and wash the soil and smaller pieces down through the larger pieces. After planting, a top dressing of a decorative stone can be added and replenished if desired but is not necessary.

In mountainous terrain, the length of the growing season is a critical factor for alpine plants. Short growing seasons as well as a nutrient deficiency in the rocky mountain soil causes many alpine plants to take on a stunted appearance. This low profile also helps to limit damage caused by wind.

For your scree garden, select plants carefully. Recognizing that most alpine plants will not grow in our climate, consider augmenting your plantings to include ground cover perennials, low shrubs and dwarf conifers to recreate a mountain moraine appearance. Be aware of light conditions and moisture requirements when choosing plants. Slow-growing specimens, which take years to cover scree area, are desirable as rampant species will get out of control. Consider the colour of the foliage, shape of leaves, structure of the plant, and colour and timing of bloom.

Choose plants that prefer well-drained soil. Sedums, which come in a variety of sizes and shapes as well as bloom colour and timing, are ideal plants with very low maintenance requirements. Sempervivum (hens and chicks), opuntia (native prickly pear) and saxifraga are also good choices. But there is a long list of other suitable plants.

Include some evergreens for year-round color and structure. Creeping or dwarf varieties come in a range of colours and shapes. Small flowering shrubs could also be considered.

Dig a hole large enough to accommodate the root ball. Remove the plant from the pot and tease the roots from the ball. Place the new plant in the hole, spreading the roots and apply some bonemeal. Replace the gravel, then water well. Water alternate days (particularly in hot, dry weather) until new growth starts to appear, then reduce watering to weekly for another month.

Except during periods of drought, watering should not be necessary once the bed is established. Remove dead leaves and twigs as necessary. Rake the scree twice in summer to obliterate any annual weeds that root in the gravel. Otherwise this garden requires no attention, can give you tremendous pleasure, and will receive many admiring looks.