Georgia Gardener Newsletter Design Tip: August 23, 2007

Landscaping a Slope

Update: This Article Generated Complaints From the Georgia Department of Transportation. Read here.

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Junipers on a Slope

Not All Slopes are the Same

When confronted with a hillside that needs landscaping, it's important to first determine exactly just how much hill you are dealing with. In mathematical terms, slope is referred to as rise over run. If you remember back to your high school geometry that would be the height attained over the distance traveled. For our purposes, we will deal with the degree angle of the slopes in order to draw thresholds for determining the best ways in which to deal with the slope you have.

Minor Slopes: Less than 20° (3:1)

For easy slopes like this, you can landscape with grass. The slope is still gentle enough to easily navigate a lawn mower. If you have a riding or self-propelled mower, it will be a breeze.

Moderate Slopes: 20-45° (2:1)

For slopes such as these, you may want to consider using groundcovers or shrubs. I prefer to use shrubs that have arching habits. Their growth habits lend themselves nicely to slopes. I recommend confining groundcovers to the bottom of the slope. If you cover the entire slope with a groundcover (such as Junipers or Creeping Phlox), you will have problems with weeds growing amongst the plants. It's a royal pain to try and remove weeds from a groundcover on a slope. Plants such as Virginia Sweetspire (Itea virginica) mixed with Muhly Grass (Muhlenbergia capillaris) work well on slopes. Remember, it's much easier to weed around shrubs and perennials than a groundcover.

Virginia SweetspireMuhly Grass

Other arching plants for sunny slopes: Forsythia, Weigela, Gold Mop False Cypress, etc.
Groundcovers for the bottom of a sunny slope: Homestead Purple Verbena, Creeping Phlox, Iceplant, Dianthus
Shrubs for shady slopes: Virginia Sweetspire, Leucothoe, Sweetshrub (Calycanthus floridus)
Groundcovers for shady slopes: Woodland Phlox, Sensitive Fern, Netted Chain Fern

Severe Slopes: 45+° (1:1)

When you get to this level of slope, it's best to consider terracing with retaining walls. A less expensive solution would be to use strategically placed boulders on the slope that can be used to retain the soil, divert and slow runoff and provide a quasi-level location for plants.

Stone WallsCreeping Phlox

Slope No-No's

I don't care how desperate you are, there are some plants that should not be used no matter how tempting. These plant may work great for now, but they will give you a migraine later:

English Ivy, Vinca major, Vinca minor, Weeping Love Grass* and Chinese Lespedeza*

*These plants are used by the "geniuses" at the Georgia Department of Transportation.

Note: Updated 9/02/07
Change Made: Reversing the slope ratios from Rise:Run (more commonly used in mathematics) to Run:Rise (consistent with Landscape Architectural standards).

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