A Guide to Types of Mulch

If you go to a garden supply store, there are usually several different types of mulch to choose from. How do you decide what is best for your native garden? What are the relative pros and cons of each?

If you have been following our 7 step guide to removing your lawn, then you have already used several types of mulch--the lawn clipping is mulch, the newspaper mulch, as well as the compost mulch. With this much mulch, why, you might ask, do you need yet another layer of mulch? These types of mulch will biodegrade rather quickly, or get washed or blown away, and will only last one season. So it is best to use a bigger material as a top layer.

Never apply more than about 3" of mulch since putting in too much in this case is not a good thing. When the mulch is too thick it keeps moisture and air away from the soil and this leads to unhealthy soil ecology and ultimate disaster for your plants. You will need about one cubic yard of mulch to cover a 100 square foot area to a 3" depth.

Before we go any further, for general garden use, we recommend either the wood chips, which is free, or the 3/4" shredded bark if you want a more finished look. But don't believe us, make your own informed choice. To this end, here is a guide on the pros and cons of the different types of mulch before you make the final decision.

  • Bark Mulch: is available as ground, shredded, or in chips. Ground bark mulch is attractive and long-lasting.

    Ground mulch is not advisable where it is gets dry and windy since the finer material will blow away, or where rain can wash it down, for example on a slope. Shredded bark or chips are a better option in these scenarios. The smaller chips will decompose sooner than the larger ones.

    Pine, Fir, or Redwood bark that is about 3/4" in size looks nice and is reasonably long lasting. They will need renewing about once every 2 years with normal wear and tear. Note that I also throw my tree's leaves on the mulch so it has company in their state of decomposition. Get 1" of mulch every two years and throw in the leaves as well. The combination works better because of the different decomposition rates, and more closely resembles what nature would do on the forest floor.

  • Wood Chips: from trees that are being pruned or cut down are always a great inexpensive mulch.

  • Tree Leaves: are free and relatively long-lasting if you use a nice thick layer. Note that tree leaves are mother nature's preferred mulch. Leaves from trees such as oak that have thicker texture make a better mulch than the leaves of trees such as maple which are thinner. The thin leaves can compact down together to form an impermeable layer, so this is not a good choice.

  • Pine Needles: are a wonderful mulch if you can get enough of it. You can always use it to supplement you other mulch like tree leaves. We enjoy the cushiony feeling of walking on pine needles, but beware that they do tend to make the soil acidic and this must be compensated for by adding some

  • Sawdust and wood-shavings: might be available free if you live near a sawmill or lumber-mill. You will probably need to add a nitrogen supplement since they will require nitrogen to decompose. You will also probably have to deal with some of it blowing off on windy days.

  • Glass clipping: can mat together forming an impermeable layer. So one thin layer will need to be put down and allowed to dry before adding another layer. Unless you have acres of grass, this is probably not a viable mulching material to obtain. Also, if you are getting it from elsewhere, you must ensure that the grass is free of pesticides and weed seeds.

  • Straw: is inexpensive and short-lived, apply about 4" deep and you would need to reapply after one year. This is more labor intensive because of the yearly renewable and probably not worth it. Also, we noticed that the straw tends to get shuffled away in more frequented areas, exposing the soil, and needs to be re-distributed more frequently.

  • Inorganic mulches: like stone, gravel, rubber, all have their uses, but not in a native garden. Since the inorganic materials do not decompose and add to the soil, they are not a good choice as a general mulch. If you are using one of these materials, then you must have a specific reason for this, that is, you are building a feature like a path, a dry creek-bed, a children's play area, etc.

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