DESIGN DILEMMAS

THE GARDEN SLOPE...What to do?

The Italians knew what to do with slopes. They took advantage of their hilly terrain and used gravity to create huge water fantasies, water steps, elaborate walls, stairways, and terraces.

An Italian hillside garden composed of broad terraces. This elaborate staircase leads over a long reflecting pool that sits on the terrace just below the villa .

The French had problems transplanting those water features to Versailles, since the region around Paris and the Loire Valley is flat. Here in the U.S. it depends on where you live...Kansas or Florida vs. the Pacific NW.

Slopes can be a blessing, or a headache. The contours of your garden space should guide your design, and will have a direct influence on how you use the principles of art…line, form, texture, and color. A truly well-designed house must be sited properly to the lay of the land. It must flow with the contours and not fight them. So it is with the well-designed GARDEN….If you have a slope, you will need to combine both aesthetic and bio-engineering principles when creating a design. The orientation of the slope will determine how it is designed and what plants are used. For example, North-facing slopes make good woodland gardens, and a garden that slopes up from the house will be far more dominant than one which slopes away.

A downward and an upward slope- one behind the house, and one infront: Plant in bold blocks of contrasting color, combine shrubs, trees and groundcovers with half-buried boulders and low walls.

'Berms'are slopes too...a berm is actually defined as 'an edge or shoulder', but in landscaping they are really seen as a raised edge, and often interpreted as a raised islandbed. They can be useful in creating interest on boringly flat landscapes, but make sure that they relate to the surrounding shapes and aren't too high or artificial looking.

A bad berm: Easter-egg hunt, anyone?


Remember...A SLOPE CAN BE A GIFT:

  • OFFERS A NEW PERSPECTIVE
  • PROVIDES BETTER DRAINAGE
  • CAN CONCEAL OR DISPLAY
  • OFFERS MORE OR LESS LIGHT EXPOSURE
  • CAN CONTROL CIRCULATION
  • 1. PLANT IT: plant roots provide structural strength and draw up excess moisture from the soil, plant foliage and debris helps to cover soil and reduce runoff.

    2. RETAIN IT: several low walls are often better on steep slopes than one high one; anything over 3 feet should be designed by a licensed engineer. Always build a wall on cut or undisturbed soil, not fill.

    3. TERRACE IT: it is often beneficial to break a long slope into several shorter slopes, or near-level surfaces to visually reduce the steepness.

    4. CLIMB IT: steps, stairways, or ramps and the percent of slope can control the rate of movement through the garden space

    5. VIEW IT: it is easier to see a garden on a slope that is tilted towards the viewer.

    Plant with a mix of material...small trees (maple and sumac), groundcovers, grasses, and perennials

    SOME SUGGESTED PLANTS FOR BANKS AND HILLSIDES

    SLOPE MAINTENANCE & PLANTING

    1. You want to maximize the spread of desirable plant cover for erosion control, so routinely remove weed plants or use a pre-emergent applied soon after planting to kill weed seeds and control weed growth .
    2. Use caution when using sprinkler systems on slopes; too much water, applied with too much force, can cause erosion, and over-saturation can cause slope failure ( a slide). Use a drip system if possible.
    3. Slopes should be designed so they do not dump water onto used areas, or allow water to drain toward a building. Use a swale or shallow gutter to carry water away.
    4. Maximum slope for a maintained landscape is 30%; for a lawn area is 20%
    5. Dead plants should be removed to minimize the threat of wild fire, since a slope will accelerate the spread of fire.
    6. When feasible, circulation pathways on a slope should occur parallel or askew to contours, not perpendicular ( which can be too steep for easy movement)
    7. Steps ideally should have 6" risers and 12" treads (a 5 ft. distance for 3ft. rise in height)
    8. Ramps require substantially more horizontal distance, with a preferred gradient of 8.33% ( a 36 ft. distance for 3 ft rise in height) Long ramps should be avoided….provide a level landing area every 30 ft.
    9. When planting on a slope, use a variety of plants with varying root depths and canopy heights. (shrubs, trees and ground-covers) Avoid using only low, shallow, even-rooted plantings, which can create a potential shear plane. A dense, deep-rooted slope will shed water, and be more stable.
    10. Plants should be dug into the slope in a shallow well, allowing the water to infiltrate and not run-off. Make sure that taller plantings are positioned vertically, and properly staked until their roots take hold.
    11. ‘Plant’ large boulders (bury 1/3rd) and add low walls when feasible.
    12. Remember to allow access for equipment (ramps vs. steps) when terracing a slope.
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