Mulching to Control Weeds

Mulching to Control Weeds Information

By Josie Borlongan, Garden Guides Contributor Mulching is essential in keeping a garden weed-free. Some of the most common materials that can be used to mulch a garden are straw, sawdust, bark, newspapers, grass clippings, and black plastic.

Mulching can slow down and, in some cases, prevent the re-growth of weeds. Mulching can also help conserve water, reducing the evaporation of water keeping the soil moist. Mulch can also absorb water from sprinkling or rain showers and can prevent soil erosion.

Site Preparation

Before applying the much, remove any existing weeds and cultivate the soil appropriately. Make sure that the weed seeds that you cover over with mulch do not have enough stored energy to germinate and grow-up through the mulch. Spray with herbicides prior to mulching makes the process of controlling weeds more effective.

Mulching Materials and Methods


* Bark, Sawdust, or Pre-Moistened Peat Moist: Apply a layer of mulch approximately 1 to 2 inches deep. This mulch is effective against annual weeds and grasses. Use pre-moistened peat moss instead of dry peat moist for the latter may be blown away by strong winds. Pre-moistened peat moss can be mixed or spaded into the soil at the end of the crop season.
* During decomposition, both bark and sawdust leach nitrogen from the soil so it may be necessary to provide supplemental feeding for plants and trees.
* Straw: Apply approximately 1-inch layer to control many of the annual weeds and grasses. Straw can be raked and tilled into the soil at the end of the growing season. Straw decomposes rapidly, so you will have to replenish it to keep the weeds down. Straw is not very ornamental and is best for a vegetable garden or over newly sown lawns.
* Grass Clippings: apply 1-inch of grass clippings to control weeds. Use grass clippings that have not been treated with chemicals. Grass clippings can be tilled into the soil as a green manure. Some grass clippings may take root and require cultivation to keep them under control.
* Leaves: Apply a 2- to 3-inch layer of leaves for good weed control. To prevent leaves from getting blown away, shred them coarsely, using a shredder or lawn mower. Avoid shredding too since they do not allow water to penetrate. Leaves are easier to avail with to use as mulch. Leaves can also help improve the soils as they decompose. Dig the decomposed leaves into the soil then add a new layer of mulch on top. Use oak and beech leaves help to acidify the soil for acid-loving plants.
* Pine Bark: Applying a 2- to 3-inch layer of pine bark is good for weed control. Pine bark is attractive mulch. Pine barks can be purchased in different sizes, from shredded to large-sized particles, called nuggets. Some disadvantages of using pine barks, especially the bigger ones, are that they tend to float in water during heavy rains and may attract termites and other insects.
* Shredded Hardwood Mulch: This type of organic mulch is good at suppressing weeds. Some advantages of shredded hardwood mulch are: it does wash away easily, it decomposes relatively slowly, and it is very attractive.
* Wood Chips: This type of mulch can be made of bark and pieces of wood of various sizes. Applying a 2- to 3-inch layer of wood chips provides good weed control. Wood chips are attractive. One disadvantage is the wood chips may attract termites and other insects.


* Newspapers: Use moistened sections of newspapers as mulch between the rows of vegetable garden plants. Avoid using color print sections of newspaper as the color ink can be detrimental. Since using newspaper alone can look messy and unattractive, you can layer grass clippings on top of the newspaper. This can serve a dual purpose, covering the unsightly newspaper and also preventing the grass clippings from taking roots.
* Black Plastic: Using black plastic is one of the most popular methods of controlling weeds but can be unattractive. Black plastics are used to block out the light so the weeds and grasses cannot grow.

* To prevent the black plastics from being blown away by strong winds, add stones, blocks or any garden ornaments to hold them down. Add a layer of grass clippings or barks to cover the black plastic to make the look more attractive. Punch a few holes so that water can still enter to nourish your plants.
* Gravel, Pebbles and Crushed Stone: Applying a 1-inch layer of small rocks will provide good weed control in a garden. These types of mulch materials are permanent and are best used for permanent plantings such as foundation plants. They are also attractive. Avoid using them around acid-loving plants for they may add alkaline elements and minerals to the soil. These materials reflect solar radiation and can create a very hot landscape environment during the summer months.
* Weed Barrier Mats: Landscape Fabric or weed barrier mats can be used to help keep weeds down. To keep them in place they must be weighted down with rocks, blocks, or stones on the ends.
* Aluminum-coated Plastic and Foil: Apply a layer of either one of these materials to provide excellent weed control. Aluminum-coated plastic and foil decompose very slowly. Some of the disadvantages are that they are very expensive and quite unattractive mulches.

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