Mulches Reduce Weeds and Improve Plant Growth

One of the best ways to reduce weeding is to apply mulch around trees, shrubs, flowers, fruits, and vegetables. The most popular mulch material is bark. Bark is available in three different size chunks and finer sizes called bark dust. Bark can be purchased in bags but is much cheaper in bulk. If you do not have access to a pickup, you can have it delivered to your property. Other materials commonly used for mulch include compost, lava rock, pea gravel, and river rock.

Most weed seeds need light to germinate. They lie dormant in the soil for years until soil is cultivated and they are brought to the surface. Placing mulch over the soil reduces light and can reduce weed seed germination by up to 90%. It requires a 2 inch layer of mulch to produce this result, but smaller amounts are also helpful.

The most effective mulch is a combination of weed barrier fabric with granular mulch. Weed barrier fabric is a black, woven plastic cloth which is porous so water and air can pass through. Polyethylene plastic should not be used as a weed barrier except for vegetables. Larger plants like trees and shrubs do not get adequate irrigation. Plant roots grow close to the surface in order to get enough air (oxygen). Trees and shrubs need deep, anchor roots for support.

When black or colored poly mulches are used for larger, heat loving vegetables, such as tomatoes, melons, squash and cucumbers, plastic strips are narrow enough so water and air can move sideways underneath the plastic, and also through holes around the plants. Poly is not covered with granular mulches because it transfers heat to the soil and reflects heat into the plants so that they grow faster.

Weed barrier fabric acts as a physical barrier to weeds, in addition to eliminating light. It will normally last for several years as long as it is covered with granular mulch, so sunlight does not deteriorate it. A few weed seeds will eventually blow in on top of the granular mulch. However, they are very shallow rooted and easily controlled.

Another advantage of organic mulches such as bark and compost is that they are converted by worms and micro-organisms into humus and eventually release nutrients to the plants growing underneath them. Typically, bark and compost mulches are added to every year or two. Organic mulches also improve water penetration and reduce water evaporation.

When organic mulches are used around annual flowers and vegetables, they are typically incorporated into the soil in the fall or early the next spring. This improves the soil and adds nutrients.

Two other readily available materials are sometimes used as mulches. Grass clippings make excellent mulch, especially for vegetables. I use grass clippings around all my flowers and vegetables. Multiple layers of newspaper make very good mulch for vegetables. However, it is necessary to put some soil on the edges to hold it in place.

We will be happy to give you a free quote for applying mulch to your property.

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