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Coping With Slopes




Although most of the Midwestern United States bears blessedly flat and level ground, there are places in which building a home on a hillside is a necessity. The foothills of the Ozark Mountains cut through southern Illinois, and the Allegheny mountains begin on the eastern border of Ohio.


Sloping property is both daunting and dangerous for the homeowner.  Slopes that are 33% (3 feet of rise for every one foot of length) or more are dangerous to mow, and soil erosion that weakens foundations and sullies waterways is an ever-present threat.  Luckily, there are landscaping tricks that can minimize the challenges slopes present and ultimately turn that slope from a liability into an asset.


Gentle slopes – those that are 25% or less – can be tamed by replacing turf with low-maintenance ground covers and hardy bulbs.  Vigorous ground-huggers such as creeping phlox, sedums, Vinca minor, houttunia and ajuga are easily grown in most soils and relatively drought tolerant.  Both vinca and houttunia work in sun or shade; houttunia and ajuga offer variegated foliage for visual interest as well.


Moderate slopes should be planted with groups of hardy perennials with mowed areas kept to a minimum.  Clumps of ornamental grasses, junipers such as the Blue Rug variety, daylilies, echinacea, rudbeckia and hostas all work well to control erosion and to create a weed-free thicket of plants.  These plants tend to be self-mulching as well, so the need to water is minimized.


Slopes greater than 33% need the intervention of a landscape architect.  Steep grades should be shored up and leveled, and this process will involve the use of heavy equipment.  After the ground is terraced and leveled, retaining walls made from decorative concrete block, railroad ties, dry stone, mortared stone or concrete need to be installed.  The materials used to build retaining walls need to be coordinated with the overall appearance of the landscape and chosen to accommodate the soil type. For example, sandy soil may be too unstable to support concrete.  Terraced hillsides can include hardy perennials, small ornamental trees, hardy bulbs, groundcover plants and turf, if the terracing is wide enough to support a mower and easily accessed.


In addition to terracing and building retaining walls, the steeply sloped hillside would benefit from the addition of a drainage system.  A dry creek bed that meanders through the garden and runs into a spillway or the street offers aesthetic and functional benefits.  Dry creek beds can be installed as do-it-yourself projects, as the trenching doesn’t need to go deeper than 18 inches, but there is considerable lifting involved in moving gravel, boulders and mortar into the area.  One caveat here is that in many areas, the homeowner needs to obtain permits from the county engineer and have his or her plans approved prior to installing the bed.  Wastewater handling is administered under the rubric of environmental protection; a drainage system such as the dry creek may affect groundwater quality.  There also needs to be adequate assurance that the creek won’t shunt water onto another person’s property.


The final touch to a hillside is the addition of stairs ascending through the garden toward the home.  Installing stairs is definitely not a do-it-yourself effort, but it may be a less costly project than would be anticipated.  Stairs can be built with a combination of pavers and stone, and may not need to have railings or banisters installed, as the width and depth of outdoor stair steps is almost twice that of the standard indoor stair step.  Concrete can also be used in most areas for stairs, but the cost of labor to build with concrete on sloping ground drives up the project cost so that it outweighs the cost to install flagstones or paving stones.


Hilly terrain doesn’t have to become a mountain needing to be moved. The right touches turn  those slopes into a painter’s canvas, and the homeowner’s yard becomes a masterpiece visible to everyone on the street below. 

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