- Organic mulches refer to mulches made from plant material. Many types of organic mulches, including shredded bark, bark nuggets, cypress mulch, aged wood chips, pinestraw, shredded leaves and composted yard trash effectively prevent weed growth. You can also use shredded newspaper or sheets of newspaper weighted down with other types of mulch. Inorganic mulches such as crushed rock, black plastic film and woven ground cloth will also suppress most weeds, although crushed rock can damage soil and black plastic film may lead to root diseases.
- Some types of mulch don't suppress weed growth, although they may benefit plants or soil in other ways. For example, straw and peanut hulls may contain weed seeds, as may uncomposted yard trash. Weeds also grow easily in sawdust. Clear or translucent plastic film doesn't suppress weed growth because it allows sunlight to reach weed seeds. Grasses may grow through the holes in woven ground cloth, although it deters many other weeds.
- Mulch may not suffocate existing weeds, so always pull weeds from the soil before adding mulch. Add a 2-inch layer of mulches composed of small particles, such as small wood chips or shredded leaves. Add a 4-inch layer of coarser mulches, such as pine needles or larger bark nuggets. Leave 1 to 2 inches of space between the edge of the mulch and the stem or trunk of the plant for air circulation. You can add mulch to trees and shrubs at any time of year, but always mulch newly established plants after planting.
- Mulching not only prevents weeds, but also prevents moisture loss, insulates the soil from hot and cold weather, prevents soil crusting and reduces erosion. In addition, organic mulches gradually improve the structure of the soil as they decompose. Mulching around trees in a lawn makes mowing easier and reduces the chances of tree damage. Many people also find the uniform appearance of mulch attractive.
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