5 methods for combating weeds without chemicals
Apr 27, 2024 10:11AM ● By Bryan Reed
At a farming conference I attended, one speaker noted, “Organic farming is weed management.”
Indeed, weed management takes a lot of energy. When chemical herbicides became available to homeowners, they offered a quick and efficient solution for killing weeds.
However, the convenience of herbicides comes with downsides, including harm to soil microbes, local water systems, native wildlife and our health.
Additionally, these chemicals have led to the emergence of stronger weeds. As of October 2023, there are 255 identified herbicide-resistant weeds in the U.S. and 523 worldwide. We’re learning that herbicides tend to harm only the susceptible weeds, allowing the more resilient ones to live on and pass on their resistance genes.
Avoiding chemicals requires a diverse set of strategies to effectively keep weeds under control.
PURE VINEGAR
The easiest transition to chemical-free weed management is using 30% acetic acid vinegar.
Household vinegar contains only about 5% acetic acid, which isn’t enough. Concentrated vinegar is now readily available in 1-gallon jugs at local garden centers. This stronger vinegar can be applied using a simple pump sprayer, ideally around midday when the sun is strongest.
The downside is that it can’t kill a plant if sprayed over the outer canopy of the weeds. It is most effective when used on young, recently germinated plants or on weeds that have been cut down after mowing or weed whacking. This allows the vinegar to permeate all the leaves and damage them beyond functioning.
SOLARIZATION
Solarization is another effective technique for managing weeds in your garden.
Before you begin planting, dig a shallow trench around the edges of your garden bed, then cover the area with clear plastic sheeting. Use the soil from the trench to anchor the edges of the plastic, making sure to seal it tightly to maximize the internal temperature. Under the right conditions, temperatures can reach up to 175 degrees F beneath the plastic, which is hot enough to kill weeds without penetrating deeply enough to harm beneficial soil organisms.
Most weeds are annuals, so once you’ve killed them, they’ll never germinate again. It’s advisable to amend the garden soil and form rows before solarizing the beds. When the plastic is removed, working the soil won’t bring a buried new crop of weed seeds up to the soil surface.
SEED TIMING
If you already have crops going, seed timing is a handy technique.
One method involves irrigating the beds to germinate weed seeds, then removing these weeds before planting your desired crops.
However, I prefer a different method: planting a monitor crop alongside your primary seed choice.
For example, when planting carrots, which have a germination rate of 7-10 days, you can also plant beet seeds at the end of the row, which germinate in 5-7 days. Once the beets germinate, you can remove the weeds without disturbing the soil, allowing the carrots to emerge within a day or two without competition.
For beet crops, planting arugula, which germinates in 3-5 days, can serve a similar purpose. While vinegar is a useful tool for this method, flame weeding is often faster and more effective.
FLAME WEEDING
Flame weeding was the primary weed management technique used in the U.S. agricultural industry during the 1930s. It fell out of favor after World War II when herbicides, developed from chemical warfare techniques, became widespread.
However, flame weeding is gaining popularity again due to its non-toxic nature. Modern farms often use implements that are pulled behind a tractor, equipped with a propane tank and flame bells that are adjusted to target the weeds directly without harming the crop foliage. This technique provides a powerful, environmentally friendly alternative to chemical herbicides.
On smaller farms, flame weeding involves using a 2-gallon backpack-mounted propane tank equipped with a single weed burner hose and bell. This setup allows the user to operate the flame with one hand while using the other hand to maneuver a snow shovel, which is used to gently lift the branches of the plants.
A low-level flame is all that’s needed; the goal is to singe the tops of the weeds, which destroys the cells responsible for photosynthesis and the plant growth hormones located at the tips of the leaves. A slow walking pace is ideal to ensure thorough coverage without overexposing any area.
If a weed doesn’t die immediately, it typically takes several weeks for the plant to regenerate its growth hormones and redistribute them to the top for new growth. Research conducted by Colorado State University at their organic farm in Fort Collins found that bindweed could regrow within seven days after being cut back with a weed whacker. However, it took an average of 21 days to regrow after flame weeding. A low flame makes for safer weeding and doesn’t use a lot of propane.
MULCHING
Mulching conserves water and suppresses weeds in your garden. Various materials can be effective depending on what you have available:
- Cardboard: Overlapping layers of cardboard by about 8 inches provides a sturdy barrier against weeds.
- Straw: Straw is another great option that also adds organic matter to the soil as it decomposes.
- Leaves: While not as effective as straw or cardboard, leaves can still serve as a good mulching material.
- Landscape fabric: This is a popular choice for long-term weed suppression.
- Newspaper: Laying down newspaper in layers about 4 sheets thick can also block light and suppress weed growth.
If you’re like me and enjoy hands-on garden maintenance, my favorite weeding hand tool is my colinear hoe. This tool features a long handle for ergonomic use, reducing strain on your back. The wide blade is perfect for a sweeping motion that cuts weeds just below the soil level, allowing for precise weeding around the bases of plants without needing to kneel. I use the model with a removable blade so I can easily sharpen it each year.
