Mulches are popular in many landscapes and accumulate naturally in forests with leaves and needles that serve as a protective layer over the earth decomposing and enriching the forest floor. That protective layer helps the gardener retard weeds, protects against temperature changes, conserves water losses, and retains soil erosion. There are many to choose from, and the selection may be confusing.
Understanding the characteristics of different mulches can help you choose wisely for your particular environment. First, consider what time of year it is. Meaning there are winter mulches used for different needs than summer mulches. Winter mulches are used as insulation for your ornamental garden plants to keep the earth evenly cool throughout winter. These include straw, shredded leaves, and pine needles. Summer mulches are applied to the soil after warming begins to decrease weed growth and retain moisture.
The right mulch for the right plant material also must be considered. Some mulch, like hardwood mulches, are too heavy and thick to allow perennials, annuals, and grasses to move and spread in the garden. Fine ground pine, shredded leaves, and wood shavings can be used for these beds. Wood chips, bark chunks, and pine needles are appropriate for shrub beds and trees.
Assuming that bark mulches have been properly stockpiled and seasoned, they seldom create a compaction problem or are susceptible to wind erosion and are good as a decorative layer in the garden and slopes. They are a by-product of milled fir, pine, redwood, and spruce logs.
Wood chips are often available from municipalities and utility companies as byproducts of pruning and clearing trees. According to Cornell University, wood chips weather faster over time. While Cornell warns that over-mulching by adding 3-4 inches layers yearly can suffocate roots of shallow-rooted species, Dr. Linda Chalker-Scott, Associate Professor and Horticulture and Landscape Architecture at Washington State University claims that organic mulches of 3” or less will promote weed growth, while 4” or more will suppress it. So consider the surroundings and what you want to accomplish in the garden. The good news is termites hate wood chips and prefer nitrogen and phosphate-rich mulch.
Pine needles have an attractive appearance and look natural around acid-loving plants. They can be found in bales at your local nursery and are easiest to spread. They decompose slowly and are resistant to compaction, letting water through. Providing excellent protection around new or tender plants, you can easily move to plant and replace without noticeable changes. It is also excellent for slopes because of its knitting properties and doesn’t wash away in rainstorms. Renew annually with a thin layer for aesthetics.
Finely shredded leaves are cheap and readily available if trees are a part of the garden. Recycling them into the beds adds a nice layer contributing humus, nitrogen, and other nutrients to the soil. If not shredded finely, though, leaves tend to mat together, blocking free water and oxygen flow to your plants and soil surface.
Consult your local nursery or mulch provider for a variety of choices and to suggest the right mulch for your garden.