Landscaping on a Slope: An Uphill battle

If you could change one thing about the property you manage, what would it be? A few years ago, I had the opportunity to present that question to an industry group during a presentation at a turfgrass conference. Overwhelmingly, the audience identified maintenance of slopes as one of the most difficult issues they face.

No doubt about it; slopes can be a headache. In fact, just about any maintenance function is more difficult on a slope, and there's no magical way around it. However, slopes can be invaluable site features for aesthetic as well as functional reasons. Learning how to cope with slopes successfully will help you get the most out of them without undue struggle.


Slopes differ. Gentle slopes are desirable because a 2 to 3 percent drop-off facilitates water movement away from buildings, yet still generally allows for adequate water movement down through the soil profile. However, when slope is 4 percent or greater, problems may arise.

The problems associated with a severe slope are of four main types:

  1. Low infiltration

    On flat or relatively flat ground, water has a longer time to soak in before runoff occurs. As the slope increases, runoff occurs more quickly and infiltration therefore decreases.

    The net result is that plants at the top of the slope don't get enough water and plants at the bottom of the slope often get too much because they are on the receiving end of all that runoff. Both results create an unhealthy growing situation for plants. The soil will be drought-prone at the top of the slope, while soggy soil at the bottom of the slope may create conditions that cause root rots.

  2. Difficult mowing

    Slopes are difficult to mow safely. When mowing a slope, the weight of the mower is not evenly distributed, leading to two problems:

    • Increased risk of overturning of the mower;

    • Difficulty in steering, because more weight is being applied to downslope wheel. The steering problem creates excessively worn turf as the wheel crushes turf plants during turning and slipping.

  3. Poor fertilizer uniformity

    Related somewhat to the problem of uneven water infiltration, fertilizer application and uptake is also problematic on slopes.

    Rainfall can cause the particles to wash down the slope. It is similar with other chemicals such as herbicides.

    Uneven chemical distribution can reduce product concentration at the top of the slope to the point where it is no longer effective. Conversely, if enough chemical washes to the bottom of the slope, it may be enough to cause phytotoxicity.

  4. Hard to mulch

    The fourth category of trouble with slopes is retaining mulch. Just as fertilizer, herbicides and water are prone to tumbling down the slope, mulch also has a hard time staying put.

In general, horticulturists and arborists are more fond of using a plant by-product as a mulch — bark nuggets, cypress pieces, stump grindings, cocoa bean hulls, cottonseed hulls, wood chips, etc. — than inorganic products such as river rock, washed stone and the newest product on the market, colored rubber tire chunks. Organic mulches are relatively short-lived, but have a better capacity to cool the soil and retain moisture than inorganics. Plus, they simply look more natural.

However, on slopes, the weight and characteristics of rock, stone and rubber allows significant advantages in terms of keeping the mulch where it belongs.

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