Do I need to add log erosion barriers if converting a grassy slope to native perennial flowers? - Ask Extension
Our new yard includes a slope that's steep enough to be challenging to mow, though that portion is only five or six yards long (see photos). We would ...
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Do I need to add log erosion barriers if converting a grassy slope to native perennial flowers? #872647
Asked June 11, 2024, 3:20 PM EDT
Our new yard includes a slope that's steep enough to be challenging to mow, though that portion is only five or six yards long (see photos). We would like to replace the grass with native perennial flowers, and got a load of wood chips to use for that purpose, but belatedly realized that the grass which currently there may be what's keeping the soil in place on the slope, and that new plants may take a few years to be established enough for their roots to fill a similar purpose. Adding logs for erosion control seems like it may help with that, but I'm not sure how thick they should be, if they need to be the full length of the area or can be smaller, if one log (or row of logs) is enough or if they should be spaced much more closely, if they need to be braced with stakes (and if so what material and size stake would be best), etc. Any guidance on how to determine what would be needed to make this conversion project safe would be welcome. Thanks.
Montgomery County Maryland
Expert Response
Unfortunately we don't have that level of detailed information regarding this kind of erosion suppression technique, and the solution may also depend on the soil texture present, so consulting with a landscape architect may be in order. You want a professional with training and experience in re-grading and soil stabilization techniques so that the slope top, which appears to be closest to the house, isn't destabilized. (Not likely, perhaps, from surface erosion alone, but we can't say with certainty what the risk may be.) Extension doesn't collect information on businesses or make company recommendations, but the Maryland chapter of the American Society of Landscape Architects might be able to point you towards a business listing. Or, the Chesapeake Bay Landscape Professional program, which provides certification in sustainable landscaping techniques (one of which is stormwater management) to the landscaping industry, might have a contacts list via their "find a pro" directory page. Your local Soil Conservation District office might also have some tips for what methods to consider using and where to find professional help.
As for more nuisance-level erosion that's not the degree of a bank stabilization threat, you could use a biodegradable barrier that's more solid underneath a wood chip mulch layer if it helps suppress erosion. There are paper-based landscape "fabric" rolls available, for example, and a layer or two of untreated burlap might also help to stabilize soil between plants if you find the wood chips too loose or prone to tumbling downhill in heavy rains. Both the paper and burlap will rot away on their own without needing removal as the new plants establish; each will probably last through one growing season before degrading. There might also be other natural-material rolls that can be laid down as a type of matted/knitted-together mulch layer, possibly made from coconut coir or excelsior (wood shavings, basically), that could serve a similar function.
Logs (whether unprocessed wood from tree removal or the manufactured coir log style) could be used like you mention to slow the water flowing downhill, since they are in essence helping to terrace the slope, but we don't know what spacing interval, and of what log length, would be appropriate for this site. (Bracing either type, though, would almost certainly be a good idea, at least if they're laid largely on the soil surface and not buried for most of their girth.)
Miri
As for more nuisance-level erosion that's not the degree of a bank stabilization threat, you could use a biodegradable barrier that's more solid underneath a wood chip mulch layer if it helps suppress erosion. There are paper-based landscape "fabric" rolls available, for example, and a layer or two of untreated burlap might also help to stabilize soil between plants if you find the wood chips too loose or prone to tumbling downhill in heavy rains. Both the paper and burlap will rot away on their own without needing removal as the new plants establish; each will probably last through one growing season before degrading. There might also be other natural-material rolls that can be laid down as a type of matted/knitted-together mulch layer, possibly made from coconut coir or excelsior (wood shavings, basically), that could serve a similar function.
Logs (whether unprocessed wood from tree removal or the manufactured coir log style) could be used like you mention to slow the water flowing downhill, since they are in essence helping to terrace the slope, but we don't know what spacing interval, and of what log length, would be appropriate for this site. (Bracing either type, though, would almost certainly be a good idea, at least if they're laid largely on the soil surface and not buried for most of their girth.)
Miri
