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Mulch has an Important Job in the Garden

Sunday, May 21, 2023

Gardening requires a few tools such as a rake, a trowel, loppers or a lawnmower, but keep in mind that mulch is also an important gardening tool.


Mulch has multiple benefits in the garden, including reduced surface evaporation, improved water penetration and air movement, soil temperature fluctuation, preventing weed growth, improved aesthetics and protection from frost/freeze damage.


There are two types of mulch available – organic and inorganic. Organic mulches include things like wood and bark chips, straw, grass clippings and seed hulls. Bark chips are often available in several colors to help blend in with any landscape. Inorganic, also known an inert mulches, include things like polyethylene film, gravel or weed-barrier fabrics. Consider what you want the landscape to look like before choosing a mulch.


When gardeners are looking for a mulch, select one that doesn’t compact easily, doesn’t interfere with water and air movement into the soil, breaks down easily and isn’t a fire hazard. Also look for a mulch that is uniform in color and won’t blow away easily in the Oklahoma wind.


How to choose the perfect mulch will depend on its purpose. Sometimes appearance is the most important aspect. In other cases, the goal may be to improve soil conditions. The size of the area needing to be mulched in relationship to the cost should also be factored in. If the garden is 80 square feet and the mulch needs to be 4 inches deep, gardeners will need 1 cubic yard of mulch. That same amount of mulch will cover 100 square feet at 3 inches, 160 square feet at 2 inches and 325 square feet at 1 inch deep.


When should mulch be applied? For those starting with seeds in the ground, wait until the seedlings have emerged. If you’re installing plants, spread the mulch after transplanting. If the soil hasn’t warmed sufficiently yet, consider delaying mulch application for a while.


Gardeners who plan to use organic material such as straw or grass clippings, keep in mind these materials may harbor rodents. They’re still fine to use, but don’t place the organic mulch closer than 6 inches to the base of woody plants. If placed closer, rodents may chew the bark on the plants which could result in plant injury or death.


Be careful to not deplete the nitrogen in the soil when using organic mulch. As the material decomposes, the breakdown organisms use some of the soil nitrogen in contact with the mulch. This may result in nitrogen deficiency. Keep an eye out for plant yellowing, particularly on the lower leaves. Adding nitrogen fertilizers can help remedy the issue.


For more information on mulches, see Oklahoma State University Extension fact sheet HLA- 6005 – Mulching Garden Soils.

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