All mulches can be divided into organic and inorganic, with organic mulches derived from natural materials that decompose over time. The two types of mulch behave very differently, and each has its pros and cons. This article will weigh the benefits of organic and inorganic mulches, and look at their pros and cons, so that the home gardener can select the mulch that best fits their situation. First we will define what mulches are organic and which ate inorganic, then we will look at four key areas where they compare.
Organic mulches include bark and wood garden center mulches, hay, buckwheat and cocoa shells, and wastes such as sawdust, pine needles, grass clippings, and lawns. Inorganic mulches include stone mulch, which is natural but doesn’t decay, as well as plastic, weed cloth, woven landscape fabric, and rubber.
Replaceable vs. permanent: Organic mulches need to be replaced frequently, sometimes annually. Inorganic mulches endure for many years at a time. This makes a big difference, as the soil can be hard to amend when using an inorganic mulch. However, inorganic mulch does not need frequent replacement. Thus, inorganic mulch often costs more but saves money in the long run. Rocks and rubber will not decompose and will need to be directly cleaned up should the mulch be removed or stray from the flowerbed over time. Inorganic mulch is not advisable for areas subject to change, such as vegetable gardens and flowerbeds with annual flowers that are changed up every year.
Biological implications, benefits, and liability: Organic mulch decomposes, enriching the soil in the process. Inorganic mulch is inert in this regard, it just sits there. Thus, when using an inorganic mulch, the absence of integrated nutrients from the mulch needs to be taken into consideration. Organic mulch can breed mold, disease, and provide cover for insects and rodents if not used properly. Inorganic mulch is less likely to be a liability in this regard. Most organic mulch keeps out weeds well. Stones often require a layer of weed cloth underneath to prevent them sinking into the ground over time. Stones and rubber require being cleaned, lest organic matter build up and give rise to weeds in the mulch. Fabrics keep weeds out well, but need a layer of aesthetic mulch to look good. If organic mulch is used over the weed cloth, it needs to be replaced as it decomposes, or it negates the weed cloth.
Implications related to ability to irrigate the plants: Organic mulches applied properly allow water to reach the plants normally. A mulch too thick or too dry can retain excessive moisture or attract bacteria that transform the mulch into a waterproof barrier; other than that they allow rainwater to naturally reach the plants. Stone and rubber do not have this potential drawback. Weed barrier and landscape fabric allow water to penetrate, but black plastic requires irrigation.
Environmental responsibility: Organic mulches often transform waste products into a useful resource as it decomposes and returns to the environment. Rock mulches do not affect the environment in their use, as the rocks are natural. Rubber mulch utilizes a waste product, but the rubber has to be removed and disposed of when it is no longer wanted or needed. Landscape fabrics and plastics often are not biodegradable and need also to be removed and disposed when no longer fit for use.
These are the benefits and drawbacks of organic and inorganic mulches, compared with each other. Homeowners and gardeners should weigh the pros and cons of each in order to make the best decision in regards to which type of mulch to use.
