Most gardeners know that mulching trees, shrubs and flower beds is a good practice, even if they may not know all the reasons. Beyond the obvious advantage of its decorative use to make plantings look clean and attractive, there are real environmental benefits that can also help gardens reduce maintenance and protect every homeowner’s investment in time and plant materials.
1. Weed Control – Most homeowners understand mulch helps reduce weeds, but best results depend on understanding why. Weeds need sunlight to germinate in the soil. The proper use of a mulch that will serve as a barrier to sunlight can help decrease the germination of weed seeds. Use a shredded hardwood or softwood material at a depth of at least 2-3 inches for best effect.
HINT: If you prefer the more rugged look of larger particles like mini nuggets or nuggets, use a 1-inch layer of shredded material first and then place a 2-inch layer of larger materials on top to get the advantages of both materials.
2. Erosion Control – Mulch is often used by highway departments to stabilize roadside embankments from erosion. The same principle applies to home gardens and should follow the same guidelines. Slopes create collection points and water flows that can carry soil downhill. The same is true of large-particle wood mulches. Since wood products often float, large particle mulch may flow downhill in a significant rainfall. Shredded hardwood mulches should be used to stabilize slopes. These materials are more dense and tend to mat together. In lighter rainfall, most shredded mulches will trap and absorb moisture thereby preventing its collection and runoff. In heavier rainfall, the intertwined particles of a hardwood mulch hold the material together.
HINT: Unfortunately, a torrential downpour on a steep incline may create more force than even the best mulch can resist; so, the steepness of the slope and the frequency of torrential rains must be considered when selecting your mulch options. An inorganic mulch like rock or stones may be your best option, especially for areas too steep to maintain plants.
3. Moisture control – On the opposite extreme from torrential rains is drought, and once again, mulch can provide needed protection for landscape plants. As a wood product with a large surface area compared to its size, mulches can absorb a significant amount of water. That retained moisture, which is released over time, can reduce the need to water plants during a drought. Even more important is the ability of mulch to allow water to penetrate to the ground while forming a barrier to reduce evaporative losses under the sun.
HINT: Retaining existing moisture is just as important to reducing water use as is the retention of new moisture. Maintain a 2-3 inch layer of loose fill mulch to allow moisture access from the top and prevent moisture loss from beneath.
4. Temperature Control – Excessive heat in the soil can damage plant roots, kill beneficial bacteria and deactivate slow release fertilizers. A 2-3 inch layer of any organic mulch can reduce the soil temperature around plant roots. In colder climates, a good mulch layer can insulate the soil from excessive cold protecting the roots from freezing. Mulch can also be piled around tender plants in a freeze.
HINT: Do not leave the mulch on above-ground stems for long in warm weather. The added moisture and heat can encourage insects to attack the stems. During the growing season, keep mulch 1 inch from the base of shrubs and trees.
New iBook Resource
For more information on the environmental advantages of garden mulch and it’s benefits to your soil, the Mulch & Soil Council has created a free iBook, Mulches for Your Home, available through the on-line Apple iBook app or the Council website at www.mulchandsoilcouncil.org. The Council selected the iBook technology platform in an effort to create a highly portable information resource with cross-generational appeal to consumers. Whether standing in a garden or roaming your favorite garden center aisles, you can access this helpful reference tool on any iPhone, iPad or laptop computer wherever you go. Interactive links also provide ready access to additional support information on a variety of gardening topics.
The iBook is written and produced by Dr. Bill Fonteno, Professor of Horticulture and Director of the Horticulture Substrates Laboratory at North Carolina State University. The many key uses and benefits of mulch applications are also expertly explained in a series of short video clips featuring gardening guru Joe Lamp’l, host of the Growing a Greener World website (growingagreenerworld.com).
The Mulch & Soil Council is the national trade association for producers of horticultural mulches, consumer potting soils and amendments and commercial growing media. Founded in 1972, the mission of the MSC is to define quality products, provide industry training, promote consumer education and encourage an open marketplace for producers of horticultural mulches and growing media.