Growings On: Taming sloping landscapes

Roger Gates

Physiography involves the study of the physical landscape features resulting from underlying geology. Ridge and valley is a descriptive phrase geologists and geographers use to describe the dominant landscape forms of northwest Georgia.

Similar geology gives rise to this landscape in a band adjacent to the Appalachian Mountains from Georgia into New York. While “ridge” and “valley” may be descriptive, most of the landscape lies between those extremes and, by necessity, is sloping. The degree of relief may range from gentle to steep, but most farmers, land managers and homeowners must manage vegetation on a hillside of one form or another.

A major challenge on sloping landscapes is the persistent effect of moving water. As water responds to gravity and seeks the lowest level, it can create substantial energy and move anything that obstructs the most direct path toward the bottom of a slope. This erosive force can remove soil, but also shallow-rooted vegetation and a gentle trickle may soon become a steep gulley.

Evidence of land management decisions made by the earliest settlers can still be observed. Some early farmers attempted to conquer nature by removing existing perennial vegetation and planting annual crops. Soil surfaces remained unprotected for extended periods and slopes that once were covered with fertile topsoil were eroded to subsoil that was unproductive and eventually abandoned.

Rather than conquering nature, contemporary homeowners and landscape managers can attempt to observe and imitate natural systems. The ridge and valley physiographic province is dominated by forest. Trees provide a near continuous canopy that redirects precipitation and offers roots and litter that cover and protect the soil surface. Forests typically are also characterized by an understory of herbaceous perennials and shrubs. Although not frequently observed in today’s natural landscapes, extensive grasslands, maintained by periodic, low-intensity fires, composed of a great variety of grasses and forbs were an important feature of historic landscapes.

Today’s gardeners can take a lesson from nature and choose plants for slopes that are deep-rooted and provide longterm cover for the soil. Degree of slope should also be considered. Soil scientists consider slopes angled at more than 20 degrees as steep. Steep slopes are at greater risk for soil erosion and extra care needs to be extended to protect them.

Even steep slopes have been farmed for centuries. The primary technique to do so successfully has been terracing. If it is desirable to produce annual plants on a sloping area, constructing a terrace is likely the best approach. Gentle steps of level areas can retain soil and provide an area that can be cultivated. Materials selected to retain soil above the terrace should be chosen to be as permanent as possible. Visualize the area above the retaining structure as a wading pool filled with water. The terrace wall needs to be substantial enough to support that weight when the soil is saturated after a heavy rain.

If landscape relief challenges your gardening aspirations, consider attending an upcoming presentation. master gardener and Extension volunteer Anna Gewecke will talk about hillside gardening on Thursday, Aug. 22, at 6 p.m. Anyone interested in hillside gardening is welcome to attend the presentation at Anna Shaw Children's Institute, 1201 Burleyson Road. The presentation is in the Southern Room.

Considerations for gardening on slopes, three methods for implementing gardens and how to prepare soil will be presented. Several alternatives and options for managing hillside vegetation will be discussed. Ms. Gewecke’s presentation will conclude with a discussion of what plants might be most appropriate for different approaches and intentions for a particular slope or hillside.

Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at roger.gates@uga.edu.

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