There are many inappropriate mulch types in use today. Let's start with mulches that satisfy very few of our conditions of what the best mulch should be and get rid of them right away:

1. Stones. Stones or gravel provide some of the benefits in that they protect the soil from erosion and decrease evaporation, but they do not breakdown and so do not do much to improve soil health. They are not one of the best mulch types.

2. Bark. Bark mulch and wood chips are no good even though they are some of the most commonly used mulching materials in the garden. You may have seen them in bags or in bulk at the garden center, or you may have used them in your organic gardening before. They do most of the above things well, but unfortunately, they have a couple of big problems making it one of the mulch types I never use.

The first is that they are very high in carbon and very low in nitrogen. This means that the beneficial microbes can pull all of the available nitrogen from the surrounding area, which often ends up causing a nitrogen deficiency in your plants.

And bark in particular is very low in nutrients (so it doesn't improve soil fertility) and often high in toxins (it's a tree's first line of defense against pests), so it causes toxicity problems in the soil. It even contains oils that repel water, rather than more appropriate mulch materials that will hold onto water.

3. Straw. Straw and Hay are not the most aesthetically pleasing, but they are fairly good mulch types. They are used in organic gardening, but the main issue for most people will be that it is not always easy to find and it breaks down so quickly that it has to be applied multiple times a year.

You may not want to use straw or hay from ryegrass as it has toxins in it, and definitely not from grass that has been sprayed with pesticides such as Roundup, which is common in many countries. The difference between straw and hay is that hay has seeds, so it will often actually produce weeds.

4. Grass. Grass clippings are not the best mulch to use in organic gardening because they get so tightly packed together that they inhibit air circulation. Besides, they are far too important for the soil of your lawn to bring into the garden. They do not contribute to thatch or any other lawn problems, but they provide many benefits so they must be left there.

5. Compost. We're getting closer to our my favorite of all mulch types, but not yet. With all this talk about organic matter, why not just use compost? A little bit of thought tells us why. It does a lot of things right, but fails to stop the weeds! The same goes with manure, and manure needs to be composted before applied to soil anyway. We can use compost and manure, but they are not really the best mulch.