Farm News

In Praise of Weeds

Brassica 'weed'

“Weeds reduce yield and quality of vegetables through direct competition for light, moisture, and nutrients as well as by interference with harvest operations. Noxious weeds are plant species so injurious to agricultural crop interests that they are regulated or controlled by federal and/or state laws.” -Knott’s Handbook for Vegetable Growers

Pick up any gardening magazine, search any website devoted to landscaping or read any textbook on farming and you will find a thousand reasons why humans think weeds are bad.

Likewise, stroll through the local garden center and take notice of the product labels. How many times do you see the words: control, combat, fight, or kill? A quick Google search uncovers HGTV which encourages us to “Learn how to identify and remove common weeds that may be taking over your lawn and garden spaces.” Meanwhile The DIY experts at The Family Handyman have a blog post titled, “How to Eliminate Weeds from Your Grass.”

This would be downright funny to me if it weren’t so sad. On the one hand, we dislike weeds because they ‘take over.’ Some people would argue that a lawn entirely composed of dandelions (a monoculture, i.e. not just one species growing in high density, but one single variety of one single species), is totally un-loveable. But on the other hand, the same people think a monoculture of turf grass is highly desirable. Why do humans think one is ugly and the other is beautiful? Seems rather subjective, doesn’t it?

At the root of all this ‘weed advice’ is a common belief about what makes a weed actually a weed. Humans are in fact, the only species on the planet to make such categorical plant distinctions based on looks. Fascinatingly, other species do preferentially select certain plants, but not for aesthetic reasons, rather for nutritional ones. Dr. William Albrecht, a prestigious soil scientist from the University of Missouri, was famous for clarifying the direct link between soil health and livestock and human health. Part of his foundational work included a study on cow forages. He determined that bovines very quickly sense if a plant is worth the energy to chew it. If it isn’t, they’ll pass over it. In a cow’s world, orchard grass, just because it is orchard grass, is not always ‘good’ to eat. If it happens to be grown in depleted soil, it may not contain adequate nutritional value to make it worthwhile.

weeds heal

Chef Dan Barber, in his book The Third Plate, highlights this aspect of Albrecht’s work. Barber writes, “Albrecht watched as cows walked past what was commonly considered “good grass” to eat seventeen different types of weeds that had been fertilized with calcium limestone, magnesium and phosphate.” He goes on to quote Albrecht: “The cow is not classifying forage crops by variety name, nor by tonnage yield per acre nor by luscious green growth,” then Barber himself adds, “but she is more adept than any biochemist at assessing their true nature. Albrecht came to the humbling conclusion that we can’t really identify a healthy pasture just by looking at it — we have to really see it, and that requires a deeper understanding.”1

For me, this deeper understanding begins very simply. It begins with the basic definition of a weed. Over and over, I hear and read this definition: Weeds are plants that grow where they are not wanted. This description is much too superficial for me because it assumes an arrogant, human-centric view.

A more accurate definition, which highlights our narrow vision and allows for other perspectives, might read: Weeds are plants that grow where humans think they do not want them.

Farming, and specifically my work with weeds, has caused me to shun the language of war and to question any impulse to judge right from wrong or good from bad. The longer I farm, the deeper my appreciation of weeds grows. Why? Over the next few weeks, I’ll share my top three reasons. For starters, here’s reason number one.

Weeds Heal. In temperate climates, Nature does not leave disturbed soil uncovered for any length of time. Bare soil is inherently unstable; it can easily be blown or washed away, cause serious erosion and the loss of important nutrients. Unstable, bare soil eventually causes the death of the millions of microscopic plants and animals that form the basis of our entire food web.

Bare soil leads to the demise of our precious topsoil. It takes “at least 100 years” to form a mere 1-inch of topsoil 2 and we human beings are absolutely dependent on this thin crust of our planet. Without healthy, living topsoil, we have no ability to feed ourselves.

(Ironic then, that it is humans who most extensively and repeatedly disturb the soil. Talk about being one’s own worst enemy!)

But as anyone who has ever tilled up a garden knows, after a soil is disturbed, Nature rushes right back in. While this is annoying to a gardener, viewing weeds from an ecological perspective is quite eye opening and anything but offensive. Weeds actually come to our rescue because they act as Nature’s first line of defense to heal the exposed ‘skin’ of the soil. Here are the attributes of weeds that make them superior soil healers:

a) abundant seed production;
b) rapid population establishment;
c) seed dormancy;
d) long-term survival of buried seed;
e) adaptation for spread;
f) presence of vegetative reproductive structures; and
g) ability to occupy sites disturbed by human activities.3

Because they establish quickly and prolifically with limited water and nutrients, weeds act as that first band-aid to protect an ‘injured soil’ from further damage. The roots of rapidly growing plants like pigweed create a network that holds fragile soil in place. Weeds shade the topsoil, (a kind of living mulch), which lowers surface soil temperatures and helps preserve moisture, both of which support the survival of soil organisms. When weeds die they contribute organic matter, which adds tilth and structure to the soil. This enables the soil to more easily absorb and store future rainfall, which subsequently assists in the establishment of a more diverse group of plants.

So ironically, weeds, for all the reasons we dislike them, are supremely suited to repair the soil we humans insist on disturbing. The logical conclusion is this: in a very important way, we owe our continued existence to the healing work of our many unloved weeds. –AJ


Footnotes

1Excerpt from Barber, Dan. The Third Plate:
Dr. William Albrecht, the longtime chairman of the Department of Soils at the University of Missouri, was born on a farm in central Illinois in 1888… He earned a medical degree but then abandoned formalized medicine because he found treating disease much less interesting, and a lot less effective, than exploring its causes. Albrecht went to the cause.

He began with a simple observation, which more or less informed his life’s work. He saw cows straining their necks to eat grass on the other side of the fence, much like the cows I had once watched at Blue Hill Farm. Why, he asked himself, would a cow risk entanglement with barbed wire when acres of pasture were free for the taking? The question… led Albrecht to discover that cows—supposedly “dumb beasts,” passive and indiscriminate about their diet—actually spend their days in one long, exhaustive search for more nutritious pasture. Cows determine their next bite by swiping their facial hairs against the tips of the grass. The hairs act like antennae, sensitive to the grass’s richness. A quick calculation is made: Does this plant hold enough nutrition to be worth expending the energy required to take a bite? In many cases, Albrecht noticed, the cows didn’t bother.

He had a hunch that these discerning diners made choices based on minerals potentially available in certain grasses. Chemistry, in other words, could explain a cow’s preference. Albrecht watched as cows walked past what was commonly considered “good grass” to eat seventeen different types of weeds that had been fertilized with calcium limestone, magnesium and phosphate. No wonder the cows deemed the other grass a waste of their energy.

“The cow is not classifying forage crops by variety name, nor by tonnage yield per acre nor by luscious green growth,” he wrote, but she is more adept than any biochemist at assessing their true nature. Albrecht came to the humbling conclusion that we can’t really identify a healthy pasture just by looking at it — we have to really see it, and that requires a deeper understanding.

2http://www.nrcs.usda.gov/wps/portal/nrcs/detail/wa/soils/?cid=nrcs144p2_036333
3List courtesy of Dwight D. Ligenfelter, Extension Agronomist, at Penn State University


“You have to have a vision. Unless you do, nature will never reveal herself.”
~Dr. William A. Albrecht

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