What makes good mulch?
This can be very confusing, particularly because what’s sold as “mulch” in many cases isn’t really very suitable for performing the full range of duties that I think mulch should accomplish (above). Briefly, I look for a material that is:
- An organic substance (meaning deriving from some living or formerly living matter);
- Fine- to medium-textured so it will break down into the underlying soil…
- …but substantial enough to stay put;
- Preferably aged before I use it;
- Dark in color (if for the ornamental beds);
- Available locally at a good price, preferably in bulk delivery unbagged;
- Not a source of contaminants, pests or diseases.
To elaborate: Any mulch I use in my ornamental beds must be fine-to-medium textured and dark colored so it looks good. Forget anything that’s going to sit there and never break down, like big hunks of bark (which I call “baked potato mulch” because they look like giant spuds sitting on the ground to me), or anything that’s bright orange. I am completely opposed to dyed mulches.
One caveat: Very fine-textured materials like sawdust do not make good mulch as they cake and fail to decompose.
Why use a product that has been aged or composted before you use it as mulch? That extra step really makes a difference in the mulch being ready to do its job as a soil-improver. Wood products in particular may also rob soil Nitrogen while decomposing, unless composted first (before they’re spread as mulch).
I used to use bagged mulches, including cocoa hulls and various bark products, many years ago. I have since switched to local materials I can have delivered in bulk, sans plastic bags (and minus all the fuel used in processing and trucking of bagged stuff across the nation to my local garden center). Environmentally, it’s important to buy locally when you can, especially with bulky items.
Technically, plants can serve as a sort of living mulch as well; that’s why certain ones are termed groundcovers.