How Weeds Heal Our Soil

I grew up pulling weeds. We would have anywhere between 80 – 120 acres of soybeans that could only be weeded with tractor-driven equipment and hand pulling the remaining weeds. We would also pull or cut thistles in our pastures and fence lines. Then there was the 2-acre veggie garden, which seemed to generate more weeds than the 80 acres of soybeans.

What I have learned in the last 40 years of research into soil and plant health is that WEEDS ARE NOT THE PROBLEM. They are the band-aid or medicine that Nature uses to heal sick, damaged soil. We can help weeds do the healing, so we will have fewer weeds and healthier soil. Nature wants to return the Twin Cities to an Oak Savanna, which was the original landscape. After decades of farming, building cities, roads, and shopping centers, our soil is pretty beat up. The whole ecosystem, our natural world, was once a thriving grassland with trees and many plant communities. These plant communities worked together to create a healthy, productive landscape that supported wildlife, pollinators, rivers, lakes and people who lived with Nature. Now we have pavement, chemically treated farmland, and weeds.

What Weeds Tell Us

There wasn’t creeping Charlie, Kentucky bluegrass, buckthorn, or dandelions in an oak savanna. These weeds are a response to unhealthy and damaged soil. Nature uses weeds to heal soil problems. In fact, you can tell what the soil problems are by which weeds are present. Dandelions indicate a compacted soil with low fertility. That big taproot will break through compaction, pull minerals up from deep in the soi,l and deposit them on top for microbes to make into food for other microbes and plants. If you let the dandelions do their work for a few decades or centuries, they will relieve compaction and improve soil fertility.

Creeping Charlie indicates a skewed pH and nutrient deficiency. Again, this weed will mine the soil for nutrients, add organic matter, and cover bare soi,l usually in the shade. Over time (a long time), creeping Charlie will change the soil and work itself out of a job.

Every weed has a soil problem to fix. Clover puts nitrogen in the soil. Crabgrass, buckthorn, and Canadian Goldenrod are all fast-growing and add lots of organic matter to the soil.

Why Organic Matter Matters!

So why does organic matter matter? Organic matter is the part of soil that is either alive or was once alive. Plants, microbes, and people are mostly carbon from the CO2 in the air. When plants and microbes die, they are broken down by microbes into a few minerals and lots of carbon or organic matter. Carbon is the fuel for plants and the soil microbe community nutrition and nitrogen is the spark. The more organic matter in soil, the healthier that soil will become. Since soil carbon comes from plants breathing in CO2, a major greenhouse gas responsible for climate change, the air will become healthier, too.

As the organic matter changes, so does the soil microbe community. In disturbed soil, you have more bacteria by weight than other organisms. A healthy soil has more fungi than bacteria. In a climax community like a prairie, pine, or broadleaf forest, the fungi completely dominate the soil biology. The driving force in this change is the amount of organic matter in the soil

The more we keep roots in the soil, leave plant residues, and keep soil covered, the faster we build organic matter.

The benefits from organic matter are increased biological function, greater nutrient content, increased structure/stability, increased water holding capacity, and improved erosion control. Organic matter creates synergies in biology, chemistry, water, and soil structure.

Pesticides & Nitrogen Do More Harm than Good

Herbicides and pesticides destroy beneficial soil microbes, leaving only a remnant of bacteria, which blossoms and creates perfect conditions for weeds and other pathogens.

Lack of microbes and excess nitrogen burning off organic matter leads to the collapse of soil structure (all the little tunnels that microbes and other soil critters make). This results in compaction of soil to the point of water is unable to infiltrate. This water pools below ground and ferments, causing bio-slime to grow on roots, resulting in roots being unable to consume nutrients or water. The excess water becomes low in oxygen and acidic, 2 conditions that weeds love.

Our feeble attempts to kill weeds with herbicides actually create conditions that encourage weeds. Leaving the microbes and weeds to correct soil problems is a process that would take decades if not centuries to complete. Most of us don’t have that kind of time. We can speed up the process by stopping synthetic inputs and focusing on soil health.

4 Principles for Finding a Balance

There are 4 principles to follow to create healthy soil. These were developed by the Natural Resource Conservation Services (NRCS), a department of the USDA, to help farmers with soil problems. The principles are broad and simple, but neatly encompass soil health.

Principle # 1 - Minimize Disturbance

Disturbance can be many things. Some need to be eliminated, while others only need to be limited. The centuries-old practice of tillage is very destructive to soil. Beneficial soil microbes and the structure (tunnels) they create are destroyed when a plow or tiller rips through the soil. Often called a “tornado in soil town”, tillage crushes microbes, soil structure, and chops up the vital fungal networks that transport nutrients and water to plant roots. Chemical herbicides and pesticides kill many of the beneficial soil microbes. The soil structure collapses with no microbes to use and maintain those tunnels. Water pools, and we get the anaerobic sludge in the soil. This is a very sick soil that will create weeds in an attempt to clean it up.

There are other disturbances, some man-made. Fires, floods, grazing livestock for a long time, logging, and construction all take a toll on soil health, but there are solutions.

Principle # 2 - Maximize Biodiversity

Mono cultures - where there is only one species of plant growing, like lawns, cornfields, etc - are inherently vulnerable. One insect or disease can cause widespread damage. Healthy plant systems have lots of diverse plants. Each plant has a role to play to help support the community. Oak trees host hundreds of species of insects. The larvae of these insects provide food for baby birds. The larvae that survive fall to the ground into a complex community of plants. Some of these plants cover and protect the soil, while others gather nutrients and cycle them for other plants’ benefit. There are plants that act as hosts for specific insects, like Monarch butterflies and milkweed.

We can mimic this diversity with companion plants in a garden, like using Marigolds to keep bad insects away. Native grasses create habitat for bees that, in turn, pollinate everybody with a flower.

Our monoculture lawns are not good for soil health and are where lots of herbicides and pesticides are used, not to mention they are a desert for pollinators looking for a meal. We can break up this monoculture by introducing pollinator plants like self-heal, yarrow, blue-eyed grass, and others. We can shrink the areas of lawn by converting turf to native plantings, which benefits soil, pollinators, and the ecosystem.

Principle 3 - Maximize Soil Cover

Often called soil armor, these are plants and organic matter, like leaves. Their job is to cover soil. Like a jacket or a blanket, they keep soil cool, or protect it from freezing, or soften the impact of rain. They also keep soil from eroding by wind or water. The best soil cover is living plant communities.

I like to plant my veggie garden thick. While it may cause some plants to produce a little less, that thick canopy of leaves holds moisture, suppresses weeds, and keeps the roots cool.

The same is true of perennial gardens. Using groundcovers to create a living mulch provides the same benefits as in the veggie garden.

There is a method called matrix design. The idea is to mimic nature and have a layered, densely planted, and interconnected design. This provides a resilient, biodiverse, and ecologically functional garden. The bottom layer is different groundcovers that will blanket the entire area and prevent weeds. Other species are added in according to layered height and ecological function. Incorporating many species of cooperating plants is a sure-fire way to achieve healthy soil and suppress weeds.

Principle 4 - Maximize roots in the ground.

The 3 previous principles will automatically create roots in the ground. One important note on roots is that natives have roots that go many if not dozens of feet into the ground. Lawn grass roots go from 3” to 12”. Some fine fescues and tall fescues go deeper, but even they can’t match the root mass of native plants.

Even in agriculture, continuous roots in the ground are achievable. The use of cover crops to be planted with or after crops will perform all of the above soil health principles. Often, cover crops consist of a cocktail of species, which gives us diversity and different ecological work being done.

Healthy Soil Means Fewer Weeds!

The benefit of healthy soil is FEWER WEEDS! There will also be fewer inputs, like fertilizer, water, and chemicals. Plants will be stronger and less vulnerable to pests and diseases. Food will have greater nutritional density. There will be less erosion, which creates healthier water. Pollinators and wildlife will benefit, and there will be less maintenance.

Here’s what you can do. Go organic with your yard. Stop using chemicals and start adding organic matter with good biology that is available in quality compost. Get rid of the marginal areas of lawn that are tough to maintain, like deep shade, boulevards, hot, dry areas, and steep slopes. Plant natives in these places. It takes about 3 years to get the soil healthy, so be ready and patient.

If you would like an assessment of your yard and soil, please reach out. I can set up a program for you to follow so you can fire your weeds! Contact me, I’d love to help!