Organic Garden Mulch: Do’s and Don’ts
Mulching your garden is one of the best things you can do for your plants and your soil. There are many forms of mulch, from organic types like wood chips to man-made plastics. Not all mulch products are created equal!
Mulching has the following benefits; it suppresses weed growth, retards moisture evaporation, moderates soil temperature and, as mulch breaks down, will improve soil texture.
For trees and shrubs, the type of mulch is less important than for horticulturists. Using the wrong mulch around vegetable plants can cause the plants to grow poorly and be susceptible to disease.
You want to choose a mulch that has a low carbon to nitrogen (C:N) ratio. The main reason for using a low C:N mulch is to ensure that all available nitrogen is not trapped trying to break down high C materials.
In nature, the first place a high C:N molecule looks for N is within the product itself. In the example of a wood chip, there is not enough N available for proper microbial growth, so the microbes search for enough N in the surrounding soil. Imagine the effect of available nitrogen to your vegetable plants if the entire soil surface is covered with several inches of wood mulch?
Worse yet, imagine if the entire soil structure was high in carbon products, such as wood chips. This would pretty much tie up all the nitrogen in your soil trying to digest all the wood chips leaving very little for your plants.
The #1 rule we give our clients is NEVER USE WOOD CHIPS, BARKS, PINE NEEDLES, or SAW DUST. On the other hand, the best types of compost are those with a low C:N ratio, such as straw, dry grass clippings that have not been treated or fertilized with chemicals, or homemade compost.
If your choice of mulch is going to be rotted manure compost, be sure to only use manure from animals that you know what they are eating. If an animal has a diet of hay that is high in salts, which is common, then its compost will also be high in salts. A medium high in salt will prevent or retard plant growth.
The best manure for composting is cow, pig, sheep, rabbit, llama, alpaca, and goat manure. The worst manure to use is horse manure, as it is high in weed seeds. Chicken and duck manure is good to use, but unless you have a professional soil test kit to test for nitrogen content, I would avoid any bird manure.
Straw mulch is our #1 choice as it is very low carbon and adds fantastic structure to the soil as it breaks down. Also, straw is very cheap and a bale of straw will last most home gardeners for a full season.