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Mulches - The Good, The Bad & The Ugly Newsletter




Mulching the bare soil around plants is a major part of the basic organic program and should be the last step when new planting is done. But, there are some good and bad choices. Here’s a run down for you and some tips that might help.

The worst choice - rubber mulch made from ground up tires. Full of toxic chemicals, doesn’t break down to feed microbes and holds heat that will damage microbes and plants. This product should never be used.

Shredded tree trimmings as shown here are an excellent mulch choice, but when plastic is used under it, the benefits are eliminated. Plus, this obviously looks terrible. Mulches should touch the soil so that their breakdown into humus feeds the life in the soil.

Shredded native mulches are the best choices. They help prevent weeds, help maintain lower temperatures in summer, protect against harsh weather in winter, recycle local materials, are loaded with nutrients, lock together and stay in place well, breathe properly and break down fairly quickly to feed microbes in the soil. The specific one shown above is shredded cedar which is an excellent choice.

Pine bark I used to recommend. The large nuggets are better than the medium and fine-textured products since they will at least stay in place a little better. The small pieces blow and wash away to eliminate the benefit and create a maintenance problem. Plus, all pine bark products contain natural chemicals that are not good for soil health or plant growth.

Cypress breaks down very slowly. That’s not what we want. The rotting of mulch is an important source of natural fertility. Cypress also tends to fuse together and not breathe properly. The way it is harvested from wetlands and shipped across the country is an environmental problem. Not a good choice.


Pecan shell mulch is a fairly good choice, if it is partially composted first. Fresh, new shells don’t behave very well. Like pine bark, they blow and wash around and fresh shells usually have some pecan meat left that attracts fire ants.


Partially completed compost is good mulch. When ingredients are still identifiable, this compost shouldn’t be used in bed preparation but it is good to use as a topdressing mulch.


Shredded hardwood bark is a good mulch. It is not as good as shredded tree trimmings because of much less nitrogen. As apposed to shredded tree trimmings, there is little protein tissue (buds, stems, cambium, leaves, etc.) that is the source of nitrogen and other nutrients.

Little closer view of shredded hardwood bark.


Closeup of shredded hardwood bark.

Pine straw or pine needles do not have the same natural chemical issues as pine bark. Plus they stay in place and work well as mulch. Only issue is that this mulch can look out of place if no pine trees are growing on the site. This is an excellent mulch for the vegetable garden because it breaks down quickly and effectively helps feed the soil.


Lava gravel is an excellent mulch if you like the look. It helps grow plants and helps keep them healthy. However, plastic should never be used under it. That destroys its benefits and hurts the soil and plants. Also, as you see here, it looks bad.

Shredded native tree trimmings in the foreground, same material in the background turned into beautiful compost by waiting a year and turning once. This is an extremely efficient way to make a high quality compost.


Tree flares should always be exposed (of course) and proper mulching should not be piled up on stems and trunks of plants. Shredded native tree trimmings shown here.


The second worst mulch choice - colored mulch. These ugly red and black products are all over the place in the marketplace but should not be used. Some of the dyes used in these products are very questionable in toxicity but there are more serious problems. These “mulches” are made from ground-up wood such as siding, palettes, lumber, etc. These things are all carbon and totally unbalanced due to lack of protein/nitrogen. They not only don’t feed the soil properly, they actually rob nitrogen from microbes and soil health.

On a second issue here - the kind of tree mulching shown here is completely inappropriate. This “volcano” type mulching looks horrible and because it is piled high up on the tree trunk, the flare is completely covered and the moisture resultantly kept on the trunk is highly detrimental to the tree.

I didn’t have a shot of cocoa mulch but it’s a bad one. It smells good but is expensive and very dangerous to dogs. Don’t use.

Here are some other useful resources from
To discuss this newsletter or any other topic, tune in each Sunday 8am - 11am central time to the Dirt Doctor Radio Show. The call-in phone number is 1-866-444-3478. Listen on the internet or click here to find a station in your area.

Please share this newsletter with everyone in your address book and all your friends on Facebook and Twitter to help me spread the word on the proper way to select, plant and maintain plants.

Naturally yours,

Howard Garrett
The Dirt Doctor


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