Mulch and Its Benefits
Mulch is any material used at the soil surface primarily to prevent loss of water by evaporation, keep weeds down, moderate soil temperature fluctuations, or promote soil productivity. This definition includes, but is not limited to a full range of organic materials such as wood chips, bark, leaves, peat moss, lawn clippings, conifer needles, hay, straw, nutshells, and more. The following information pertains to organic wood chips and bark mulch in your landscape. Click here to learn about common inorganic mulches.
Why Mulch Under Trees
Trees and grass growing together compete for moisture and nutrients. Mulch in place of grass under trees eliminates grass competition, providing a more favorable environment for the tree to thrive and grow.
Mulching also helps reduce nutrient and soil loss from erosion, and helps keep the soil temperatures at a tolerable level. By mulching under trees, you can also reduce the need for mowing, and reduce damage to trees caused by weed trimmers and mowers.
Proper Mulching Process
- Mow existing grass where mulch will be placed as short as possible.
- Place a layer of newspaper over the mowed area, to help suppress growth of weeds and grass. Spraying the grass with herbicide such as "Round-Up" can also be effective.
- Spread mulch to create a mulch ring three to six inches thick, going out to the drip line if preferred.
- Pull mulch back one inch from the trunk to avoid trunk rot.
Maintenance
Over several years, your newly mulched space can become a naturally wooded area. You can selectively keep desirable plants and remove undesirable ones. A little weeding a few times per growing season should be all that is necessary.
Each year a portion of your mulch will slowly decompose, providing organic material for your trees and plants. Every few years apply a fresh new chip layer one to two inches thick over your existing mulch, as needed.
Commonly Used Inorganic Mulches
Rock Mulch is a commonly used material in many landscapes. It can be appropriate in some areas, however it is difficult to maintain in an area with trees. Rock Mulch is heavy and does not blow away, and there is no need to replenish it. Some disadvantages to rock mulch are expense, holds in heat, does not add organic matter to soil, and is difficult to keep free of leaves.
Plastic Weed Barriers under mulch create problems in the landscape. Plastic under mulch eliminates aeration and promotes anaerobic conditions, impedes moisture infiltration, traps heat, and accumulates leaf-litter over time. This leaf litter provides an organic layer for weeds to germinate on top of the plastic.
Fabric Weed Barriers have few benefits that plastic barriers do not. Fabrics suppress broadleaf weeds and are permeable, allowing moisture and gas exchange. Similar to plastic barriers, fabric weed barriers can accumulate leaf-litter and provide an area for volunteer seedlings and weeds to germinate.
Over time rock mulches and weed barriers are difficult to maintain and are expensive and time consuming to replace.