Mulch Madness

June 26, 2025

Mulch Madness

It’s my goal to cover bare soil at FECO, both in the garden beds and in the tree guilds. You can see a variety of living and non-living mulches at FECO. See photos of of various plants and other materials: Hazelnut shells, early-flowering borage (Trachystemon orientalis), straw, leaves, prunings and recycled paper, and the edible living cover crops of dandelions, chickweed (Stellaria media) and purslane (Portulaca oleracea) – very nutritious!

I was reminded of the importance of covering bare soil while reading the June, 2025, Fruit Grower magazine. The article pertains to vineyards but the concepts hold for bare soil anywhere.

Excerpts from an article by Mary Retallack, PhD (Viti/PlantProtection), in the June, 2025 Good Fruit Grower, pages 24-27:

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“In arid Eastern Washington, nearly every vineyard features bare soil beneath the vines, thanks to herbicide or cultivation practices growers deploy to reduce competition from weeds.”

But Dr. Retallack sees the tradition of bare ground as a roadblock to Washington’s quest for sustainable wine production. As founder of the National EcoVineyards Program, Mary and her organization are dedicated to increasing the resiliency of Australian vineyards through improved soil health and functional biodiversity. 

“Please cover your soils wherever you can. Bare soil puts the microbes on a starvation diet and the soil becomes like concrete, with little to no water infiltration.” (Microbes need air, water and food.)

She counts the earthworms in a shovelful of soil as a good test of the soil ecosystem. She states that earthworms help drip irrigation penetrate the surface, but the soil must be covered with plants to attract worms! Earthworms create channels to aid water infiltration and root growth, and microbes and earthworms poop out nutrients right where you want them. For a cover crop, Mary recommends drought-tolerant native plants that provide shelter, nectar, alternative food and pollen for beneficial insects.  (https://retallack.com.au/publications/)

Growers worry that mulch, including living (grown at the same time as the crop) or non-living  cover crops, compete with your ‘cash’ crop for nitrogen, water or nutrients. Yes, you can find studies that show that production is reduced when paired with a living mulch (squash and broccoli). There are also studies showing no interference with production.

Over the years I have learned that the New Mexico universities have very good information related to growing plants with less water. (Very logical!) In a New Mexico State University publication, Principles of Cover Cropping for Arid and Semi-arid Framing Systems, the author writes that moisture utilization by the living cover crops is counterbalanced by the improved infiltration, lowered soil temperature, improvement of soil health and reduced evaporative losses when no-till and minimum tillage systems are employed. Living cover crops also suppress weeds and provide pollinator habitat.

Plant selection is key when choosing a living cover crop. A positive relationship may abound when you consider crop families and root structures (e.g. onions with a mixed grass and legume as a living mulch).

Many other forms of mulching over bare soil are available, if living cover crops seem complex. Cover crops can be grown during the “off-season” and then composted in place before the cash crop season begins.

Articles also mention reduced compaction with plants versus bare soil. Here’s is a simple compaction test for soil that you might try: Push your garden fork in soil that has not had anything growing in it and then push your fork into the soil where plants have been growing. Do you notice a difference?

What mulches do you use where you garden to cover bare soil?

Ruth

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More References and Resources:

Enhancing Biodiversity in the Vineyard – Workshop Notes
Retallack, Mary, no date (don’t you love that)

Click to access Enhancing-Biodiversity-in-the-Vineyard-Workshop-Notes.pdf

Mulching – Keeping Soils Covered
Davis, Mary Tebo, University of New Hampshire, July 15, 2021
https://extension.unh.edu/blog/2021/07/mulching-keeping-soils-covered

Landscape Mulch for Water Conservation
Feehan, Kelly, University of Nebraska at Lincoln, April 30,2 024
https://water.unl.edu/article/lawns-gardens-landscapes/landscape-mulch-water-conservation/