Much Ado About Mulch
More than once I’ve pulled a back muscle lugging around hefty bags of mulch, so the idea of a “green mulch” alternative has immediate appeal to me. But I think you’ll find there are many other good reasons, beyond injury prevention, to rethink our reliance on shredded wood as a fixture in our gardens.
A Bit of History
If you’re as old as I am (the exact same age as George Clooney, if you must know), and you think back, you may recall that hardwood mulch hasn’t always been a thing. Our annual ritual of spreading thick layers of wood products on our bare dirt is a relatively new phenomenon.
It started around 1970, with the passage of the Clean Air Act. The law prohibited sawmills from burning their leftover sawdust, wood chips and tree bark, which is how they had previously disposed of their by-products. Around the same time, the U.S. Department of Agriculture’s Forest Service issued a paper lamenting that “surplus bark” had become “the most perplexing residue problem” facing the timber processing industry and proposing some solutions. After outlining the barriers to using bark as fuel or in construction materials, the report landed on the idea that one of the most attractive “low-grade outlets” for excess bark was to package it as mulch. The authors said, in so many words, that if you squinted at bark from the right distance, it could kinda be considered a “soil conditioner.” They went on to predict that creating “a new industry” of selling bark as mulch would “boost the economy by making a valuable asset out of a costly waste.” They also noted that bark would encounter competition from other materials in the mulch market, so “bark product manufacturers” were advised to “advertise their wares vigorously and strive to educate the public in their use in order to gain wide consumer acceptance.” In other words, the USDA counseled the lumber industry on selling us a product we didn’t need and hadn’t asked for.
The Mad Men of the 1970s apparently understood the assignment. Fast forward to 2022, and many of us have internalized as gospel that tidy beds of fresh, dark mulch are a required ingredient in our gardens. I’m no exception – I have the lumbar strains to prove it! Stroll around most neighborhoods in the US, and turfgrass lawns and pine bark mulch will stand out as the dominant features of residential, commercial and public properties alike. We spend upwards of a billion dollars a year on the stuff.
What’s more, mulch made from lumber byproducts has taken on a life of its own. Its original purpose as a soil conditioner – however contrived that rationale may have been – has been overtaken by its role as decoration. Intentionally or not, people use it instead of plants. In nature, plants grow cheek-to-jowl in communities. But in many of our gardens – mine included – plants are spaced like little islands of green in an ocean of mulch. In keeping with the decorative function, we now have dyed mulches (available in red, brown or black and won’t fade for a year) and even rubber pellets manufactured to resemble shredded pine bark (won’t fade or rot for 12 years).
The Purpose of Mulch
To be clear, mulch is neither a bad nor a new thing. Surely humans have been devising ways to cover bare soil for as long as they’ve been practicing agriculture. It’s useful for deterring weeds, conserving moisture, and moderating soil temperatures. In addition to wood products, people have used pine needles, hay, compost, manure, leaf litter, seaweed, landscape fabric, oyster shells, gravel – and probably many other materials. There is definitely a place for mulch in a new garden that’s getting established or in areas with heavy foot traffic.
That hardwood or pine bark mulch, though? It’s cost- and labor-intensive to put it down every year. It doesn’t do much for the soil. If we pile it too high, it kills plants by suffocating roots, promoting fungal and bacterial growth, or altering the composition of the underlying soil. The practice of building “mulch volcanoes” around tree trunks is particularly damaging. (In fact, if you’re bound and determined to mulch a tree, there’s a 3-3-3 rule: pile it no more than 3 inches deep in a 3-foot radius from the tree and with a 3-inch gap right around the trunk.) In addition, wood mulch provides no benefit to insects, birds or wildlife.
Maybe Give Green Mulch a Try?
“Green mulching” simply means using living, growing plants to fill in between other living, growing plants. These plants can be short, medium or tall, depending on your functional and aesthetic needs. Native plants are ideal for this purpose, because they can provide all the benefits of pine bark mulch (moisture retention, weed prevention and sun protection) without the downsides. AND they provide habitat, food and pollen for your backyard ecosystem. AND they’re beautiful. A win-win-win-win.
By creating layered plant communities in your garden, including trees, shrubs and herbaceous perennials, you’ll attract more songbirds, butterflies and bees. By combining plants that naturally congregate together in nature, you’ll be creating a system that’s self-reinforcing. Best of all, perhaps, you’ll get to enjoy a lush, year-round tapestry of flora and fauna.
Don’t worry, you don’t have to go cold turkey. For example, you can add a handful of native groundcover plants to your beds and, as they spread to fill the spaces between more established plants, cut back on the wood mulch over time. You’ll want to choose plants that suit your ecoregion (see here for more on that topic) and the particular site you have in mind, taking into account soil composition, light conditions and moisture levels. Focus on plants that spread easily but won’t be so aggressive they’ll crowd out everything else. Whatever you do, avoid invasive species. Ixnay on the vinca minor and English ivy, for example. You can use seeds, plugs, flats or potted plants, depending on your budget and time horizon. Your local native plant society is probably the best resource for ideas, but you’ll also get help from the National Wildlife Federation’s native plant finder.
For most of us, there will be dozens of plants to choose from. In the past I’ve relied on plants that are known for their foliage rather than their flowers for our groundcovers – aiming, I guess, for a sort of minimalist aesthetic. There are certainly plenty of native species in that category. But what the heck, what about flowers? That’s what supports and attracts the pollinators, after all. Just to give you some inspiration, here are just a few of the flowering “green mulch” options that are suited for my neck of the woods.
Aren’t these more fun than an ocean of rebranded lumber industry byproducts?
Resources:
Brandon Everett and Louise Schaefer, “Living Mulch (Part One) – an Ecological Alternative to Wood Mulch,” Edge of the Woods Native Plants website, July 10, 2019.
John M. Harkin and John W. Rowe, “Bark and Its Possible Uses,” Forest Products Laboratory, U.S. Department of Agriculture Forest Service, Revised 1971.
Adrian Higgins, “Americans Love Mulch – and Many of Us Are Misusing It,” Washington Post, September 13, 2017.
Deborah Smith-Fiola, “Problems with Over-Mulching Trees and Shrubs,” Rutgers Cooperative Research and Extension Fact Sheet, Revised April 2000.
Thank you, Lolly, for shedding so much light on mulch and for offering really good alternatives!
Good to see creeping phlox on the list! I have that. I also have ajuga, I wonder how that is for the job and the bees