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| There are two basic types of mulches, organic and inorganic. Organic mulches include formerly living plant materials such as wood and bark chips, pine needles, straw, and grass clippings. Inorganic mulches or inert mulches include rocks, gravel, polyethylene films and weed barrier fabrics. Organic Mulches
The use of organic mulch is one of the seven principles of Xeriscape. Organic mulches, such as wood chips and bark, offer the following benefits:- They reduce surface evaporation from the soil.
- They improve water penetration and air movement.
- They moderate soil temperature fluctuations.
- They protect shallow-rooted plants from freeze damage and frost-heave.
- They look good.
- They discourage weed growth.
- They improve soil structure and nutrient availability as they decompose.
Won't It Blow Away?
People often complain about mulch blowing away during windstorms. Our experience at the Xeriscape Demonstration Garden has been varied. We have experimented with several different types of mulch--large bark, small bark, cedar chips, aspen chips, pine needle and cone mulch, and what we call 'generic' mulch - a combination of ground wood, bark, leaves, sticks, etc. Our findings? Generally the 'generic' mulch is not only less expensive, but it is also more likely to stay put. When applied to the recommended depth of 3 to 4 inches, the mulch tends to form a mat or knit together, and is less likely to blow. To assist in the knitting process, wet the mulch, especially during the first few weeks and during prolonged dry, windy winter periods. There are other variations to the generic mulch - the recycled pallet materials also mat together. Processes are available to dye the mulch, and there is also a fine textured 'twice tumbled' mulch. These stay put, but are a little more costly. Won't It Attract Slugs?
Another question we frequently hear is, "Does the mulch encourage slugs?" Slugs like a moist environment,and mulch in an area that is constantly damp may be more prone than others to slug problems. Remember the purpose of the mulch is not to stay wet all of the time, but rather to maintain the soil moisture and to insulate the plant roots from summer and winter temperature extremes. If the mulch is located next to a bluegrass area that is watered on an every-other-day schedule and there is sufficient over spray on the mulch bed, the mulch will stay wet like a sponge and tend to harbor creatures that like wet conditions. To counteract these problems, adjust sprinklers to avoid over spray, plant ground covers which can take advantage of some unavoidable over spray, and finally, but most importantly, don't overwater turf areas. Applying Organic Mulches
Mulch should be applied on bare soil with an edging around the area. We do not recommend the use of plastic or landscape fabric under organic mulch because the mulch breaks down over time. This is actually an advantage over rock or other inorganic mulches, because as the mulch breaks down it is improving the structure of your soil. Top-dress organic mulches every other year or so. One cubic yard of organic mulch covers 80 square feet at a depth of 4 inches. Inorganic Mulches
Inorganic mulches such as gravel, stone and sand offer many of the same benefits as the organic mulches. However, over time, windblown soil and decomposing leaves build up on top of the rock. Without on-going maintenance, rock mulch becomes unsightly and creates the ideal environment for noxious weeds. Further, rock mulch creates a generally hotter and drier environment in the landscape. The use of rock mulch should be limited. If rock mulch is used, place it over a permeable weed barrier fabric. Clear or black plastic should never be used over the roots of trees or shrubs as it inhibits the movement of air and water to their roots. |
