Organic mulches such as shredded bark, wood chips, bark chips and others are commonly used on landscape plantings. As with anything, they have both pros and cons although few would argue that the advantages do not outweigh the few disadvantages.

On the plus side, organic mulches on ornamental beds and borders help to conserve moisture which helps reduce the amount of irrigation needed. It also helps keep the plants growing at an even rate uninterrupted by periods of drought stress.

A two or three inch layer of mulch makes it difficult for most weeds to emerge into the sunlight. This greatly reduces the amount of hand weeding or chemical herbicides needed for a bed.

Mulch also has an impact on soil temperatures. For some plants such as clematis, high soil temperatures are detrimental to maximum growth. A layer of mulch during the summer helps keep the soil cooler. Conversely, in the winter, mulch will help to keep the soil frozen and prevent the damaging effects of the alternate freezing and thawing of soils called heaving.

Since these mulches are organic in nature, they too will decompose over time. This will result in an organic layer which is an excellent place for earthworms and other desirable organisms to thrive.

Finally, organic mulches look good. The aesthetic properties of much should not be forgotten. A uniform layer of mulch on all beds in an area will bring a sense of unity to the layout. It will help tie the beds together and make them look as if they all emerged from the same plot.

There are some negatives to the use of organic mulches but these are generally minor. Of course, there is usually some cost involved with using the mulches listed above. Whether purchased by the bag or by the cubic yard, it costs money to put down mulch. Also, it has to be applied which takes time and it may need to be replaced over the years as it decays.

In extremely rare instances, plant diseases may be spread by mulches. The most serious potential seems to be in the spreading of certain root rots by using the mulch made from trees that were infected. The best bet is to use materials that have been partially "composted" by setting in a pile for six months or more. This will help to minimize this problem.

As these mulches decay, they become excellent breeding grounds for slugs. When the mulch becomes water soaked and slimy, slugs love it. So, if this pest is a problem, instead of adding new mulch on top of the old, rake up the old and put it in the compost pile. Replace it with fresh, new mulch.

Finally, some people do not like the fact that most mulches lose their looks over time. The crisp, bright color of the fresh mulch fades away as it ages. There are even products available to spray on the mulch to keep it looking fresher longer.


Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

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