Organic Vs. Inorganic Mulches: And the Winner Is…

In a garden battle that has been waged for decades, mulch vs. mulch, there are pros and cons on each side. But which type of mulch is best for your garden, and why?

Mulch is one of the best things you can do for your garden! Applying mulch can enrich the soil, conserve water, prevent erosion, block weeds, and keep plant diseases at bay. Most mulches are simple and easy to apply, and inexpensive.

But what is the best type of mulch for your garden?

There are dozens of different ways to mulch your garden, but all types can be categorized into one of two groups: organic mulches, or inorganic.

Here are some of the pros and cons of each type, to help you decide which is best for your garden!

Organic mulches include formerly living material such as chopped leaves, straw, grass clippings, compost, wood chips, shredded bark, sawdust, pine needles, and even paper. Inorganic mulches include gravel, stones, black plastic, and geotextiles (landscape fabrics).

Both types discourage weeds, but organic mulches also improve the soil as they decompose. Inorganic mulches don’t break down and enrich the soil, but under certain circumstances they’re the mulch of choice. For example, black plastic warms the soil and radiates heat during the night, keeping heat-loving vegetables such as eggplant and tomatoes cozy and vigorous.

Using Organic Mulches

There are two cardinal rules for using organic mulches to combat weeds. First, be sure to lay the mulch down on soil that is already weeded, and second, lay down a thick enough layer to discourage new weeds from coming up through it. It can take a 4- to 6-inch layer of mulch to completely discourage weeds, although a 2- to 3-inch layer is usually enough in shady spots where weeds aren’t as troublesome as they are in full sun.

Wood Chips + Bark Mulch
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Shredded Leaves

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Grass Clippings

Grass clippings are another readily available mulch, although it’s a good idea to return at least some of your grass clippings directly to the lawn as a natural fertilizer…. It’s fine to collect grass clippings occasionally to use as mulch, and the nitrogen-rich clippings are an especially good choice for mulching vegetable gardens. Your vegetables will thank you for the nitrogen boost!

Compost
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Pine Needles

Pine needles are a trim-looking mulch for garden beds. They allow water to pass through easily and they break down slowly. Despite what you may have heard, using pine-needle mulch will not make your soil significantly more acid.

Straw + Hay
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Advantages

Spreading organic mulch saves labor and nurtures plants….

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Limitations

Unfortunately, nothing is perfect. When using organic mulches keep in mind the following:

As low-nitrogen organic mulches such as wood chips and sawdust decay, nitrogen is temporarily depleted from the soil. Fertilize first with a high-nitrogen product such as blood meal or fish meal to boost soil nitrogen levels.

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In damp climates, organic mulches can harbor slugs and snails, which will munch on nearby plants; don’t spread mulch near slug-susceptible plants.

Organic mulches are usually more or less acidic, depending on their content….

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Plastic Mulch

Mulching a vegetable garden with sheets of black plastic film can do wonders. When it’s spread tightly over a smooth soil surface, black plastic will transmit the sun’s heat to the soil beneath, effectively creating a microclimate about three degrees warmer than an unmulched garden. Because the plastic film remains warm and dry, it protects the fruits of vining crops such as strawberries, melons, and cucumbers from rotting and keeps them clean. And of course, the mulch prevents weed growth and retains soil moisture.

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Because water can’t permeate plastic, the mulch retains soil moisture but it also keeps rainwater from soaking the planting bed. Thus, the ideal watering system for a plastic-covered bed is soaker hoses or drip hoses laid on the soil surface before you put down the plastic.

Don’t use plastic as a mulch under shrubs. Although it keeps out weeds and can be camouflaged with decorative mulch, black plastic destroys the shrubs’ long-term health….

Plastic Imperfections

Although black plastic mulch seems like a great boon to organic gardeners, its use is not problem free. One issue of concern with black plastic is its manufacture (it’s a petroleum product) and its disposal—there are very few places it can be recycled. If you carefully lift black plastic at the end of the growing season and store it in a dry place over winter, you should be able to reuse it for several years, but eventually if will become torn and you’ll have to throw it away.

An alternative is a biodegradable plastic mulch (cornstarch based)….

Unlike black plastic, landscape fabrics let air and water through to the soil beneath while keeping weeds from coming up. But landscape fabrics (geotextiles) have some of the same drawbacks as black plastic….

For more about organic vs. inorganic mulches, see the full article at Rodale’s Organic Life

Rose S.

An avid gardener since childhood, I love sharing my passion for gardening with others! I have gardened in a number of different climates and settings, from large fenced garden plots, to tiny patio and container gardens, and I firmly believe that everyone can learn to grow at least some of their own food - no matter where you live. Growing your own food can help you take control of your own health and food supply, and there has never been a better time to get started!


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