I believe that mulching in the garden is one of the key components of a healthy soil ecosystem and growing healthy plants.
Many of you have been to my garden and greenhouse. One of the questions I get is why all the paths between our raised grow beds are mulched so heavily? The natural assumption for most people is that we do this to control weeds and grasses. My laziness is partly the reason. However, there are other, more important considerations.
You need to have a little better understanding of our garden design. All of our grow beds are at least 12” deep while many of them are deeper. We build our beds using construction grade lumber with no preservatives impregnated into the wood. These grow beds are open-bottomed. The soil in the grow bed is in full contact with the soil beneath them.
We need to understand what is going on in healthy soil. Healthy soil is teaming with life. From the smallest forms, the microbial organisms like bacteria, protozoa, and fungi, to the larger specimens such as earthworms and other multi-legged creatures. These all have a role to play in a healthy soil system.
One of the biggest players in this complicated web of organisms is the mycorrhizal fungi, which serve as the virtual living arteries within healthy soil. Fungi colonies in healthy soil form a vast interconnected web that can span thousands of square feet. This pathway or artery is how nutrients and water move to the plant’s roots from well beyond the plant’s ability to spread roots. The fungi and plant form a symbiotic relationship in which the plant exudes carbohydrates in the form of sugars through its roots, and the fungi provide water and nutrients in exchange. This exchange happens in several ways. If you are interested in this process, there are hundreds of research papers available that have studied these processes in detail.
The mulch that covers the areas outside my growbeds serves several purposes. One, it does keep down unwanted weed and grass growth and makes removing those that do gain a foothold much easier. More importantly, it allows the infiltration of rain into the soil and then acts as a protective barrier for the soil and keeps that moisture in place. This protection also extends to the microbial life in the soil, keeping the soil cooler in the heat of summer and warmer in the winter. The protection from the harsh UV light of the sun allows the organisms in the soil to work at the underlayer of the mulch, converting it into more soil.
The Expanded Soil Ecosystem
Because the beds are open-bottomed, the soil ecosystem between the beds connects to the soil ecosystem in the walkways. That mycorrhizal fungi colony can extend from the plants in the grow beds to the full extent of the area around my garden, creating a huge nutrient and water “well” from which the plants benefit. My walkways become a virtual “pump,” providing a rich source of nutrients and water to the plants.
My choice of mulch is wood chips. I try to source fresh local wood chips when I can. Fortunately, there are several sources of free wood chips available in our area.
You see, there is a method to my madness beyond my laziness and wish to keep the weeding, mowing, and weed-eating to a minimum in the garden. Mulching the pathways around my grow beds makes them a productive part of my garden rather than a maintenance nuisance.
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