Digging Deep: How to Suppress Weeds Organically Without Chemicals
December 21, 2021
Weeding is one of the most important tasks to get under control if you want your farm or garden to be productive. As weeds grow, they create shade and also require their own use of water and soil nutrients, competing with your crops (“crops” are the plants you have purposely planted for production). Weeds have evolved to adapt to most growing conditions in order to survive, meaning, not only will they survive in drought and low fertility — they may thrive in it. In a garden of healthy, established weeds, your crops won’t stand a chance.
It’s important that we analyze the usage of the word “weed” before we go any further. This word is thrown around, in my opinion, quite flippantly, to designate or label any plant that is growing in a spot where we don’t want it. The thing is, weeds are plants, and they grow where they grow for many reasons.
“Weeds” are plants that have actual names and carry many beneficial properties that are helpful for us to become familiar with. These plants are sometimes invasive and can be nuisances that require their removal — but not always. Some of these plants are actually lovely — some are beautiful, and many are edible and quite delicious and nutritious (hello purslane and chickweed!) Some of these plants enrich the soil, leaving nutrients behind after they die off. All weeds prevent harmful soil erosion, because anything with a root ball does.
Related: Foraging My Yard: Early Spring in WNY
I’ll stop there — The benefits of “weeds” is a topic for another post. I do want it to be noted here though, that not all “weeds” are bad, nor should they necessarily be referred to as “weeds.” In order to coexist with nature in her current non-natural state (as humans have been manipulating the land for hundreds of thousands of years and even the wildest of what’s left, in its current state, is neither “wild” nor “pristine”), we must gain respect for these plants. And in order to gain respect for them, we must get to know their names and properties…
Our flower farm in 2020
legendary Wendell Berry once said:
“We have the world to live in on the condition that we will take good care of it.
And to take good care of it, we have to know it.
And to know it and to be willing to take care of it, we have to love it.”
Regardless of the love-or-hate relationship you have with the weeds in your farm, garden or yard, we know that, in general, a weed-free garden bed is best practice for growing a successful crop of vegetables or cut flowers.
The biggest challenge of growing organically, based on my 10 years of experience, is keeping the weed growth in check without the use of herbicides. I’ve grown in over 150 gardens over the past decade. It goes without saying: the bigger your plot is, the more opportunities you present for weeds to become a problem. Below is commentary on all of the ways I have attempted to suppress weeds using organic methods.
How to suppress weeds in organic farming, gardening or landscaping without using chemicals
#1 Rule = Get to the weeds before they go to seed
If there is any “big mistake” I’ve made in growing my flower farm, it is that I let the weeds go to seed in multiple areas of the farm. I let this happen because I didn’t have enough time nor person-power in my first two growing seasons to pull all of the weeds out before they produced seeds that then dropped/scattered all over the rest of my farm. My biggest word of advice — DO NOT LET THIS HAPPEN. I will be performing damage control on the weed seeds for years to come due to my negligence.
If you remove the weeds before they are fully mature/dropping seeds all over the place, then you won’t ever have a weed problem.
Learn How to Identify Weeds — this is super important!
Know what you’re working with. You need to know the invasive weeds that need removal ASAP (mugwort, bindweed, gooseneck loosestrife, wild grapevine, pokeweed). You need to know which ones propagate new plants from tiny pieces of broken roots (mugwort and motherwort, I’m looking at you two). It would be nice to know which ones are edible so you can use them for a delicious salad or pizza topping (purslane, dandelion, chickweed, purple dead nettle, clover blossoms, lamb’s quarters, queen anne’s lace greens & roots). You should know which ones fix nitrogen from the atmosphere and deliver it to the soil at their rhizosphere (root ball) after they die, making that nitrogen available for your crops (clovers, vetch and legumes) — in which case, if they’re not overtaking anything, you might choose to leave them be.
Knowledge is power when dealing with “weeds.” It simply does not work in your favor to go over all the weeds with your hoe, thinking it’s helping when it may be hurting. I learned (and continue to learn) to identify the weeds on my farm by taking photos of them and googling later on. I will also find local extension office lists of weeds per state or region of the country and look through all the photos, learning about the weeds I have. It’s a journey that has helped me understand these plants in a different way — their way. Once you arm yourself with plant knowledge, you’ll be able to make better decisions about who can stay and who has to go.
No-Till Approach
Not tilling your soil is the best, most important decision you can make for your farm. Tillage (even “light” tillage) destroys microbial systems and soil structure, leading to soil compaction, low organic matter, low nutrient levels, low soil moisture holding capacity… etc. No-Till farming and gardening is an entire topic in itself — I’ve written extensively on the subject of no-till and encourage you to become familiar with the benefits of this method.
Tillage, which kicks up layers of soil, exposes millions of weed seeds in the process. When these formerly dormant weed seeds are exposed to fresh air, sunshine and moisture, guess what they do. They germinate! You can avoid exposing millions (billions? trillions?) of dormant weed seeds by leaving your soil alone.
Learn more about no-till farming/gardening here - 5 Steps to Building Healthy Organic Garden Soil, Part 1
Apply Organically-derived Mulch
Using a thick layer of mulch after planting is beneficial for many reasons — mulch blocks light and prevents weed seeds from germinating; it keeps soil temperatures lower in the hottest parts of the summer; it holds moisture and prevents soil moisture from evaporating; it breaks down over time and contributes to soil organic matter; and it even tucks in and protects soil microbes from harsh conditions during all parts of the year, including winter.
My favorite mulch to use is shredded leaf mulch, which I collect from the side of the road where my neighbors’ landscapers have dumped it. The shredded leaves provide a thick, cozy layer of insulation and over time, are broken down by worms and soil microbes into a rich black gold that ups the organic matter in the soil. “Organic matter” is anything that has been added to the soil that was previously alive, such as rotted leaves, stems, small sticks, flower heads, etc. that has broken down and provided food for soil microbes. Organic matter also holds onto moisture, so having a lot of it in the soil is beneficial to help reduce the need for excess watering.
Related: Fertilizing and “The Law of Return” <— all about using shredded leaves!
Other great organically-derived mulches:
Straw (avoid Hay, which contains seeds)
Woodchips (to be used in abundance for perennials but avoided for annual plants, as woodchips tie up nitrogen, a necessary nutrient that most annual plants need in abundance)
Compost (technically compost is not a mulch but rather, it should be used as a microbe inoculant for your farm; however, when weed-free compost is used in a thick layer on top of your growing bed, the compost is very effective in suppressing weeds below).
Mulches to avoid using in organic gardening:
Bagged mulch that has been dyed
Hay or Straw bales that have visible seed heads
Peat Moss (not a mulch nor a sustainable material to be using for any reason)
Wood mulches on annual plants (ties up nitrogen)
More commentary on using mulches for winterizing the farm/garden here — Winterizing the Flower Farm Using No-Till Soil Building Techniques
A mixture of leaves and woodchip mulches add a plethora of microbial activity to the soil — evidenced here by visible mycelium on woodchips
5. Using Paper Mulches
There are two types of paper that can be used effectively to keep weeds down — 1) plain old cardboard, and 2) rolls of thick paper for construction purposes, such as this type. Because both of these options are natural and biodegradable, they can simply be layered on top of an existing garden bed, covered with a thick layer of new soil, and planted directly into. Applying cardboard and thick paper this way does a phenomenal job of keeping weeds down. Worms absolutely love cardboard and paper and will eat it up, leaving behind a rich layer of worm castings.
I’ve made entire new gardens using this cardboard layering system, usually referred to as “Sheet Mulching” (read my Cardboard Sheet Mulching tutorial here). Entire new gardens can be created by layering cardboard, leaves, and new soil or compost, without digging up any grass. Similarly, these materials can all be layered on existing gardens to suppress weeds.
Biodegradable paper mulch added on top of a layer of straw.
A thick layer of compost added on top of paper mulch.
Tips for using cardboard MULCH & paper mulches
Make sure to use cardboard that only has black ink. Colored and white inks are derived from chemicals
Cardboard requires 6-8 weeks to soften/break down before digging holes in it for planting. Paper can be immediately planted into using my favorite garden tool - a dibber.
If you’re planning on mulching with builder's paper, look for a roll that is the width of your bed (36” or 48”). I add leaf mulch to the bed, then roll out the paper, then cover with 2-3” of fresh compost.
Always err on the side of reusing cardboard boxes rather than purchasing new cardboard or rolls of paper, when you can. We want to reduce our consumption as much as possible.
6. using burlap
Burlap is an effective material to use to permanently keep leaf mulch in place on a crop of perennial shrubs or trees.
Visit this blog post for step-by-step instructions on how to use burlap on perennial beds and This Post for winterizing annual beds.
7. Woven Plastic Landscape Fabric
A common material in the commercial farming world, woven plastic landscape fabric is an incredibly effective tool to suppress weeds. On our flower farm, we use Sunbelt brand landscape fabrics as permanent pathways to keep weeds under control. In much of the perennial section of the farm, the plants are actually planted into the fabric where holes have been burned using a handheld propane torch.
Here, landscape fabric is used on planting beds and pathways on our farm in 2019.
There are pros and cons to using landscape fabric, which I have detailed in this blog post here <—Lots of good info in there about how to use landscape fabric! Keep in mind that landscape fabric is made of woven plastic and carries a heavy carbon footprint. As such, I am working on using less of it in the future.
Below is the brand of landscape fabric we use on our farm and highly recommend, in either 3-foot rolls or 6-foot rolls. Rolls in 6-foot widths can be burned in half with a handheld propane torch. You’ll save money this way!
8. Silage Tarping / Occultation
To effectively clear a large area of weeds or overgrowth, placing a Silage Tarp on top of the area for several months will kill most annual weeds underneath. A Silage Tarp is a thick (yet easily movable) sheet of plastic with absolutely no holes in it. Typically, one side is black and the other side is white. Silage Tarps come in all sizes, although commonly they are very large (50’x100’, 100’x200’, etc) but can be easily cut in pieces to fit smaller areas, if necessary. The act of using a Silage Tarp to suffocate vegetation (usually weeds or cover crops) is called “Occultation.”
Silage Tarps work because once an area is covered, everything underneath the tarp is suffocated. The tarp will initially trap heat, causing dormant weed seeds to germinate, then once the seedlings are deprived of sunlight and moisture, they will die underneath. After several months of tarping, the Silage Tarp will effectively kill most annual weeds and cover crops underneath. Perennial weeds will need an entire season of coverage before they die (although I doubt that amount of time would kill the most noxious ones — mugwort, I still see you).
I have some qualms with Occultation, in that I’m not sure how healthy this method is for soil microbial life when the soil is being suffocated for months and months on end. I choose to use this method when an area is so weed-infested and overgrown that I can’t possibly deal with pulling it all out by hand. I dealt with the very back overgrown part of my farm using silage tarping and it worked splendidly. I do not, however, plan on using Silage Tarps to kill weeds in already-established garden beds. The environment seems much too harsh for the soil life I have worked so hard to create.
Related: The Difference Between Regenerative, Sustainable, Organic and No-Till Farming
The overgrown part of the garden has been covered with Silage Tarp and held down by heavy rocks.
After a few hot summer months, the Silage Tarp has killed off the weeds underneath.
8. Living Pathways
If you’re starting a new farm or garden in a grassy area, the easiest way to maintain pathways (and weeds in pathways) is to simply leave the grass where it is. Grass is a wonderful weed suppressant, and if your garden/farm beds are wide enough, the grass will not encroach on your growing space. Anywhere there are roots growing in the ground, good things are happening: soil microbes are being fed, soil erosion is being prevented, and atmospheric carbon is actually being sequestered! If you have the opportunity for grass pathways, consider it. Keep the pathways the width of your mower and it will be incredibly easy to maintain!
If you don’t have grass already and want to establish a living pathway, white clover is a wonderful option. White clover is low-growing and therefore does not even require mowing. It is one of the earliest spring bloomers, providing a spring feast for bees when they need it most. Best of all, it is drought tolerant requiring no water, and it does a great job perennializing itself in thick clumps, preventing other weeds from growing through the fibrous roots. The easiest way to establish a clover patch or pathway is to scatter seeds by hand — here is a great White Clover seed option for that.
White clover grows in thickly and makes a great walking pathway material.
9. Ensure You’re Using Clean, Seed-Free Compost
There is absolutely NOTHING WORSE than spreading weed-filled compost all over your beautiful garden beds. This is, most definitely, worse than letting all of your plants go to seed (at least that was your fault and you had some control over it). Weed-filled compost, on the other hand, is an absolute nightmare and if you’re not careful, you won’t know the compost is full of weeds until they start growing in your garden. Weed-filled compost has been a problem everywhere I’ve gardened — from Michigan to Illinois to New York State.
My general rule is, I don’t use municipal compost (it’s filled with more than just weed seeds — try gardening in chemicals and trash!). Nor do I use compost from landscape suppliers anymore (try gardening in aggregates and rocks the size of your head). My go-to compost solution is sourcing animal manure (particularly cow or a mixture of cow/horse) that has been fully composted (finished) by a local farmer. They need to have made it themselves and know what went into it, and if any weed seeds are present.
To learn more about sourcing compost, read this — Outsourcing Compost and the Risks Involved
Related: How to Start a Biodiverse Compost Pile
10. Embrace the Weeds (as cover crops)
That might sound counter-intuitive, but hear me out.
All types of vegetation that grows out of the ground can essentially be used as cover crops — this includes weeds. The purpose of cover cropping, in regenerative farming systems, is to: keep the soil covered; keep the microbes fed, and in turn, keep the microbial activity going; add organic matter to the soil once the cover crop cycle has ended; and overall, add nutrition to the soil by keeping that organic matter in place.
Taking all of the benefits of cover cropping into consideration, if there is a garden bed you need to keep fallow for part of a season, or if you have a thick cover of weeds growing on your garden beds at the end of the season… why not just leave them be, as if they were cover crops?
That’s exactly what I’m doing in one of my annual beds at the flower farm. One bed is decidedly weedier than the others, and I made a choice at the end of the season to just leave the weeds in place and let them enrich the soil over winter.
Allowing the weeds to act as a cover crop over the winter will keep the soil insulated and protect from erosion. This annual bed has grown a mixture of dead nettle, motherwort, queen anne’s lace and re-seeded borage.
Should you have any other ingenious earth-loving tips to keep “weeds” in check, I’d love to hear them — leave a comment below!
peace, love, plant magic & happy weeds,
Fran Parrish
