Organic vs. Non-organic Mulch

mulchQuestion: What is the difference between organic and non-organic mulch and which is better?

Answer: Mulch serves several purposes. It can help conserve water, suppress weeds, protect plants over the winter and give a “finished” look to the garden. Organic mulches are derived from something that was once living. They will decompose over time, and some types can add nutrients back into the soil as they do. Non-organic, or inorganic, mulches are made of materials that were never alive. They will not break down over time.

Organic mulches include bark nuggets, grass clippings, straw or salt marsh hay, compost and chopped leaves. Of these, bark nuggets decompose slowest. Compost provides the most nutrients as it degrades.

Inorganic mulches include gravel, black plastic and landscape fabric.

As to which is better—organic or inorganic—it depends on how you feel about costs, garden maintenance and aesthetics.

Organic mulches need to be replaced as they decompose, so they represent a recurring cost. However, you may be able to avoid this cost if you use your own materials, such as compost you make yourself or shredded leaves from your own deciduous trees.

Gravel does not break down, so it is a one-time cost, but light-colored gravel can increase heat and dryness around plants—which may be good or bad, depending on the likes and dislikes of your particular plants.

Landscape fabric can be expensive, but it does a good job of blocking weeds when installed properly. It looks better with an organic mulch, such as bark nuggets, laid on top; however, as the bark nuggets break down they will form a layer of soil in which weeds can grow, defeating the purpose of the fabric. Topping the fabric with another inorganic material, such as gravel, avoids this problem.

Avoid black plastic around permanent plantings of trees, shrubs and perennials. It does not let air and water reach the soil. Plastic is better applied around annual food crops, such as strawberries or tomatoes. It should be removed at the end of the growing season and replaced the following year. You’ll have to also install an irrigation system under the plastic, or water the plants carefully by hand to be sure they get adequate moisture.

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Related: Can I use oak leaves for mulch or are they too acidic?

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Learn about all methods of making and using compost in The Complete Compost Gardening Guide.

Get 5 illustrated techniques for improving your soil for $3.99 in Smart Gardening Techniques: Soil.

Easily clean up gravel-mulch areas, gently rake the garden and even collect pine needles or maple seeds with the Wizard rubber rake.

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6 thoughts on “Organic vs. Non-organic Mulch

  1. I agree that rubber mulch does not seem appropriate to cover plants, however if we are recycling rubber tires and preventing their addition to landfills, then I think they are fine for pathways through the garden. The kind that is formed in mats would also reduce the problem of weeds growing in the mulch.

  2. From many years of gardening experience: Stone is NOT recommended since it is a non-renewable and non-sustainable resource. Over time it fills with organic matter and sprouts weeds (defeating it’s purpose). Being non-organic it does not breakdown and add any nutrients for plants. However it is very useful if there are areas of soil erosion where even dense plantings do not hold the soil in place.

    Landscape fabric is a disaster since weeds root into it once there is any organic matter on top of it. If any changes are required in the plantings the fabric must be pulled up or it must be cut to make openings. Rubber mulch (which can catch on fire) is also not desirable. Do we need petroleum products buried in our gardens? No!

    • Re SGP comment: No mulch is entirely without maintenance requirement. The ones mentioned probably have the least. Landscape fabric is best with stone on top. But it all depends on the circumstances and the look desired.

    • A bit more mulch-talk. Mulch should rarely be used as a design element (exceptions being decorative stone such as beach pebbles or glass mulch). Mulch is typically needed to reduce weed seeds sprouting, moderate soil temperatures, and add organic matter to the soil. Ideally plantings are spaced properly so they knit together and block the view of the ground/mulch. If the view is blocked then sunlight is usually blocked and that cuts down on weed seed germination. As plants lose their leaves they tend to self-mulch as well. In many areas mulch dyed red is available but should be avoided unless the plants are so unattractive the mulch needs to be the focal point. All mulch means some cost and/or labor but the rewards are great.

    • Hi, Bob — you’re right, strawberries are technically short-lived perennials and an initial planting of June-bearing cultivars will yield a harvest for 3 to 5 years (generally). They perform best with a yearly renovation that allows new runners to replace older plants; the runners will bear the most fruit the next year. Day-neutral or everbearing varieties are best treated as annuals, however, to be plowed under and replaced each spring, because their yield declines dramatically each year.

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