Homeowners have many decisions to make when adding to or creating a new landscape that may include raised beds filled with flowers, herbs or vegetables. Considerations such as selecting the proper species of shrubs and trees, along with sun, shade and water needs are definite “to do’s” that will help create a successful and flourishing landscape. Mulch, an additional piece of the landscape puzzle, has many benefits (with some drawbacks) and there are oodles of types to choose from. To avoid using the wrong mulch, learn the facts and unearth the mysteries of mulch to find the right fit for you.
When considering all the options, it’s helpful to understand the benefits mulch provides in the landscape. These include weed control, conserving soil moisture, reducing soil erosion, providing uniform soil temperatures, protection from weedeater and lawnmower damage and adding aesthetic value to the landscape.
Mulch falls into two categories: organic and inorganic mulches. Organic mulches are natural items such as pine needles, bark, wood chips, leaves and lawn clippings; they tend to decompose or break down over time, adding organic matter and improving the soil’s structure. The disadvantage with organic mulches is the need for reapplication every so often.
Inorganic mulches such as lava rocks, pebbles, plastic and landscape fabric offer the benefit of fewer reapplications, but fail to enhance the soil’s organic matter. Additionally, it’s more cumbersome to add, divide or move plants within inorganic mulch than with organic mulch. Black plastic as another option tends to discourage weeds, but it prevents oxygen and water from reaching the plant roots unless helped with drip irrigation. Landscape fabric may be an alternative choice with products that function similarly as plastic but allow for normal water and oxygen exchange. These materials are placed on bare soil around trees and shrubs with mulch added on top. With this practice, it’s important to realize that the added “on top” mulch will eventually decompose, producing a layer of “soil” in which weeds will grow. Coarse-textured materials, such as pine bark nuggets, decompose more slowly.
When navigating the various mulch options, think about the aesthetic value and its resistance to compaction, winds and washing away from heavy rains. When it comes to visual appeal, pine needles, bark nuggets, compost and crushed rock provide the best look in the landscape. In addressing resistance to heavy winds and rain, the majority of the mulches do fine except on steep banks. On occasion pine needles become displaced with strong winds and bark nuggets are known to float away after heavy rains from water run-off. Overall, most of the mulches resist compaction, implying they fail to stick together to form a layer that prevents water from getting to the soil and roots. Exceptions include lawn clippings and leaves. Both will compact easily over time and create a barrier lessening the movement of water and oxygen to the plant roots. If lawn clippings or leaves are used as a mulch, compost them prior to application in the landscape.
Mulch can be applied any month of the year. However, the best time for established plantings is in the spring after the soil begins to warm, before the plants begin to grow and the germination of weed seeds. Apply mulch to the entire bed or to individual trees, at least 6 inches away from the trunk to help prevent bark decay and vole damage; and as far out as 6 inches or so beyond the drip line of the tree. Renew as needed to maintain a 2-inch to 3-inch depth of mulch.
Finally, avoid the “volcano” look. This practice of piling up deep layers of mulch against the trunks of trees not only suffocates the roots but encourages voles and other pests. If your trees have the “volcano” look, pull excess mulch away from tree trunks, ensuring a two to four-inch layer of mulch extending out to the edge of the tree canopy.
Christine Bredenkamp is NCSU horticulture extension agent for Jackson County.