10 Reasons to Use Mulch in the Landscape

Mulch comes in many different flavors, from shredded hardwood to pine needles to hay to bark chips, and may include inorganic materials like chipped rubber. But why should a gardener bother with mulch? What possible benefits are there in blanketing the ground under plants with the stuff?

Mulches can enhance the garden experience in many different ways.

The Benefits of Mulch

1. Mulch insulates the ground. It keeps roots cool in summer and warm in winter. This insulating quality also speeds seed germination in the spring.
2. A 2″ to 3″ layer of mulch helps retain soil moisture, decreasing the need to water frequently, thus preserving water while making it more available to the plants during hot months.
3. Well-maintained mulched beds tie planting masses together and add to the beauty and harmony of a landscape. Mulches come in many colors and textures. Gardeners can usually find one that works aesthetically with other garden elements.
4. The edge of a mulched planting bed can define the boundary between the lawn and planted areas.
5. Applications of mulch can deter weed development. Before planting shrub beds, gardeners should place a layer of newspaper on the ground. Dig through the newspaper to set the plants. Water well, and top dress with 2″ to 4″ of mulch. Most weeds won’t be able to gain a foothold.
6. Mulch does a good job of hiding drip irrigation lines, valve boxes and other landscape utilities.
7. Decomposing mulch adds nutrients to the soil and improves the ability of the soil to transfer moisture to the plants. Increasing organic matter in the soil also helps it percolate excess water.
8. Mass shrub plantings benefit from the application of mulch, but so do trees, or combination plantings. Planting beds or individual trees scattered throughout a turf area can be tied together with an application of mulch that encompasses them all, creating unity and making it easier to mow.
9. Sometimes mowers or string trimmers can damage plant stock. Creating a mulched planting bed that extends several inches wider than the planted area can serve as a buffer to protect the plants from over-zealous landscape crews. This works especially well if an edge element (like commercial steel edging, brick or a foot edge) is installed to keep the mulch in bounds.
10. Mulch can also cushion planted areas, roots and underlying soil from the impact of foot traffic, and negate the force of falling raindrops to decrease the chance of erosion.

Correctly Applying Mulch

In an article in the September 2009 edition of Total Landscape Care entitled “Getting the Most From Mulching – Do You Mulch Too Much?”, Cindy Ratcliff explains that like too much of anything, going overboard on the mulch can be bad for plants.

Ms. Ratcliff says that gardeners should apply mulch to a depth no greater than 2″ to 4″. When mulching around newly planted trees, leave a 3″ to 4″ space between the mulch and the tree’s trunk. Leave an 8″ spacing for mature trees.

The thickness of the mulch gardeners apply will depend on their plant’s moisture needs and soil drainage abilities. For permeable soils, 2″ to 4″ of mulch is plenty. As the soil becomes more impermeable, decrease the mulch depth. Permanently waterlogged soils may need no mulch at all.

Avoid creating what the International Society of Arboriculture terms the “mulch volcano”, where mulch is piled high and thick on the base of a tree. Mulch volcanoes can create an environment for disaster, causing root suffocation and dehydration. They also can become transfer vectors for fungal growths, pathogens, insects and animal pests. Mulch volcanoes also live up to their name – decomposition causes them to heat up, generating temperatures up to 140 degrees Fahrenheit. Soon, all that remains is a dead tree erupting from a mulch volcano.

Mulch Maintenance

After some time in the elements, mulch deteriorates. Gardeners should top dress planting beds with fresh mulch either annually, or when the mulch has decomposed or compacted to a depth of 1″ or less.

Some mulches, like pine park, are notorious for floating away in runoff from heavy rain. Use shredded hardwood in areas subject to inundation, like rain gardens, or on sloped areas where rainfall may sheet flow in high volumes. Avoid using organic mulch in swales or areas of concentrated runoff. Instead, substitute an inorganic material such as river stone or lava rock. Other options: create a dry stream bed, or use a ground cover plant suitable for erosion control.

Mulches are inexpensive, protect valuable plantings, and enhance the landscape both aesthetically and functionally. No garden should be without these multi-purpose materials.