The Safest Weed Killers for Vegetable Gardens


For centuries people have been fighting weeds in their vegetable gardens. There are some tried and true methods for killing them that have been passed down through time. But there are also some newer things like herbicides that are quite effective. All herbicides are not created equal, though. Some are safe to use around your vegetables, and others are not.

What are the safest vegetable garden weed killers? The safest ways to kill garden weeds are to mulch, use a weed barrier, and cultivation. You can also use scientifically-proven safe herbicides like:

  • Corn gluten meal
  • Pendimethalin
  • Trifluralin
  • Natural oil products
  • Acetic acid products
  • Herbicidal soaps
  • D-Limonene
  • Sethoxydim
  • DCPA
  • Glyphosate

Whether you choose to pull them by hand or use a safe herbicide, it is possible to get the weeds out of your vegetable garden. If you do it by hand, try to disturb the soil as little as possible. If you use herbicides, it is essential that you carefully read the labels.

Safe Weed Killers for Vegetable Gardens

It is always safer if you don’t introduce chemicals to your vegetable garden. Here are three of the safest ways to get rid of weeds.

Mulching

Mulching is one safe way to control weeds in your vegetable garden. Mulch can be natural or inorganic. Some examples of organic mulch include shredded wood, cocoa hulls, pine bark or needles, and straw. Inorganic mulches include recycled rubber, fabrics, and plastic.

When you cover the ground with mulch, it prevents the seeds close to the surface from receiving enough light for germination. That means fewer weeds in your vegetable garden.

If you put a thick enough layer of mulch on your garden, it can also smother germinating seedlings.

One thing to note is that organic mulches won’t prevent perennial grasses from growing through the barrier. If you have well-established weeds, you will need to remove them before you lay down the mulch.

Killing the weeds is not the only benefit to using mulches. When you cover the soil, you also slow the rate of evaporation. That means that you are preserving most of the water for plant use. This is especially important during dry weather.

Use a Weed Barrier

Another option you have to remove weeds from your vegetable garden safely is to use a weed barrier. Landscape fabric is excellent for preventing weed growth because it blocks out all of the sunlight.

You can either buy a ready-made barrier, or you can make your own with strips of black plastic or even an old carpet. If you decide to do it this way, make sure that you use pieces or strips. You don’t want to use a solid piece of plastic or carpet because they would prevent water from getting to the soil.

Newspaper is another excellent barrier to use in your garden. You can make the barrier look better by covering it with mulch.

Dig, Pull, and Hoe

This is not the easiest method of killing weeds in the vegetable garden, but it is useful. You just need to be very careful around the roots of the vegetables. When you hoe up weeds, you should make sure that the blade is sharp. Use it to slice through weed roots just beneath the surface.

Just remember that whenever you loosen up the soil, you are also exposing any weed seeds to the light, potentially causing them to germinate. So be careful that you don’t disturb the dirt too much. If your weeds have longer roots, you can use a garden knife, a hand weeder, or a dandelion digger.

Are Herbicides Safe to Use in Vegetable Gardens?

When it comes to killing weeds in vegetable gardens, not all herbicides are created equal. Some herbicides are safe to use around edible crops, and others are not. Some will actually damage the vegetables. I can’t stress this enough. You must read the labels on the herbicide thoroughly to be sure that the application is safe.

The best way to deal with weeds in your vegetable garden is to use cultural techniques like mulches and cultivation. Use herbicides only after reading the label. Herbicides are best for spot treatments or specific crops.

Types of Herbicides

Here are some of the terms that you need to know if you’re going to use herbicides in your vegetable garden:

Pre-Emergent Herbicides

Pre-emergent herbicides, also known as “weed preventers,” kill weeds as they sprout from seeds. They work by forming a barrier against germinating seeds. You can use these herbicides by working the product into the soil by watering it in, or you can do it manually.

As I said, the label will tell you how to use the product safely.

It’s important to note that these herbicides don’t kill the seed or prevent weed seed germination. Instead, the pre-emergent herbicide limits the root system development of the seedling. They prevent the weed from ever establishing.

Pre-emergents won’t control existing weeds. But they will control seedlings of perennial or annual plants if you apply them before germination.

Post Emergent Herbicides

These herbicides won’t stop new weeds from sprouting from seeds. They will, however, control existing weeds. The label on the product will tell you the right amount to use and the correct timing.

There are two types of post emergents. One will burn back the portion of the weed that is above ground, but typically these won’t kill the root. The other is absorbed and transferred through the weed plant, destroying the source.

These herbicides work best when they’re well-timed. The key is to use it when the weeds are no taller than six inches. Some plants may require several applications.

Selective Herbicides

Herbicides are either non-selective or selective. Selective herbicides will kill some plants but not others. These are useful in controlling weeds in the lawn because they will kill weeds like thistles and dandelions, but they will not kill the grass.

Selective herbicides can be useful in killing weeds in vegetable gardens. But you should read the label on your product carefully to be sure that it is safe to use around fruits and vegetables. Some are, and some aren’t.

Non-Selective Herbicides

The problem with using non-selective herbicides in vegetable gardens is that they kill or damage all plants. They will kill the weeds, but they’ll also destroy your veggies. So if you use non-selective herbicides in your garden, you must be careful not to let the chemicals touch the vegetable plants.

Non-selective herbicides can be useful for killing weeds in places like along fences or in cracks in the sidewalk or driveway. If you use this type of herbicide, you must use caution around your desirable plants.

Contact Herbicides

Finally, herbicides can be classified as systemic or contact. Contact herbicides will only kill the part of the weed that you spray. With contact herbicides, the root system is not destroyed. That means that the plant will likely grow back.

Systemic Herbicides

Systemic herbicides will kill the entire plant. When you use systemic herbicides on weeds, the product is absorbed by the plant and carried into the root system, effectively getting rid of the weed entirely.

Herbicides Safe to Use in Vegetable Gardens

These ten herbicides are safe to use in your garden. But it’s worth noting that you have to be careful with all of them and utilize proper safety measures. At the risk of sounding like a broken record, the most important thing is that you thoroughly read the labels.

1. Corn Gluten Meal

Corn gluten meal is an organic product that you can safely use to control weeds in your vegetable garden. It is a pre-emergent herbicide. It contains 10 percent nitrogen. So it can double as a fertilizer.

Research done by Iowa State University showed that corn gluten meal stopped the germination of many weed seeds. However, it’s worth mentioning that it’s not always effective on all weeds.

When you use corn gluten meal in your garden, you may have to do repeated treatments to get rid of the weeds.

2. Pendimethalin

Pendimethalin can be used to control weeds around many different types of vegetables. It is a selective herbicide so that it won’t kill everything. 

You can use pendimethalin as a pre-emergent or an early post-emergent. You incorporate this herbicide by irrigation or cultivation. And it is available as a wettable powder, emulsifiable concentrate, or dispersible granules.

Read here for more information about pendimethalin.

3. Trifluralin

Trifluralin is a pre-emergence, selective herbicide. It can be used on many different grain crops, vegetables, nuts, and fruits. And it is effective on many broadleaf weeds and annual grasses.

To apply this herbicide, you add it to the soil by mechanical means. It should be incorporated into the soil within 24 hours of application.

You can add granular trifluralin by overhead irrigation. This organic herbicide is available in emulsifiable concentrate and granular formulations.

You can learn more about trifluralin here.

4. Natural Oil Products like Weed Zap

Weed Zap and other natural oil products are organic. They contain natural oils like clove oil and cinnamon.

These herbicides are contact, non-selective products that can control actively growing weeds. Because this is a contact herbicide, only the parts of the weed covered with the spray will be affected. It does not absorb throughout the whole plant. So it won’t kill the root system.

You can also use Weed Zap as a burn-down product or for spot treatment. Just be careful not to make any contact with the vegetable plants.

5. Acetic Acid Products like SummerSet AllDown Concentrate

These organic products contain vinegar (acetic acid). Some also contain citric acid. These are non-selective contact herbicides that are safe and effective for controlling weeds.

You will likely have to use multiple applications, especially for more substantial weeds or perennials.

This is a safer alternative to glyphosate. Acetic acid products break down rapidly in the environment, and they generally have low toxicity. But you have to be careful not to let the product touch your vegetable plants.

You can use this product selectively by drenching, spraying, or painting. One downside with using this type of herbicide is that it is usually quite expensive. You may also find quality differences between different batches.

Read more about acetic acid products here.

6. Herbicidal Soaps

Herbicidal soap is another non-selective, post-emergent, contact weed killer. These organic herbicides work best on succulent, young weeds that are less than five inches tall. They work better on small, actively growing plants than on larger woody weeds.

Several re-applications will be needed because perennial weeds can show regrowth. You can also use herbicidal soaps as burn-down materials and spot treatments. But you should not let the product get on your vegetable plants.

According to the University of Arizona, herbicidal soaps contain fatty acid salts. These salts break down into carbon dioxide and water. They work by disrupting the cell membranes, and they only kill the tissue that they contact. 

7. D-Limonene

Researchers at Georgia Tech University have found that using a combination of vinegar, clove oil, and d-Limonene was effective at controlling and killing weeds in vegetable gardens. D-Limonene is the oil found in citrus fruit skins.

This organic material works by destroying the waxy cuticle of the weed. D-Limonene is a non-selective, post-emergence herbicide. Like the others, it can be used in vegetable gardens, but you must be careful not to get the chemical on your crop plants.

8. Sethoxydim

Sethoxydim is a post-emergence herbicide that is safe to use in vegetable gardens. Poast is the most common brand of sethoxydim. This product will only kill weed grasses. It won’t affect broadleaves.

Poast can be sprayed directly over the top of many vegetables. For your exact crop, check the label.

You should apply Poast to grass weeds before the plant reaches eight inches tall. For most annual grass, you will only need one application. But if you want to control perennial grasses like bermudagrass, then several applications may be required.

9. DCPA (Dacthal)

DCPA, sold as Dacthal, is another effective weed killer safe to use in vegetable gardens. Dacthal is a selective, pre-emergent herbicide, and it can be used to control weeds around root vegetables like potatoes, onions, and turnips, as well as plants such as broccoli, cauliflower, and cucumber.

DCPA must be used before the weeds emerge. It will provide weed control for up to two months after planting.

You can learn more about DCPA by reading here.

10. Glyphosate

Roundup or glyphosate is the most common herbicide used in home vegetable gardens in the United States. It’s popular because it’s so effective. It is a broad-spectrum product that can kill many weeds, including perennial and annual grasses, trees and shrubs, and broadleaf plants.

You apply glyphosate to actively growing plants. It works by absorbing throughout the plant. According to Michigan State University, glyphosate “inhibits the enzymes involved in the synthesis of the aromatic amino acids: tyrosine, tryptophan, and phenylalanine.”

The weeds then begin to die as a result of the process. Annuals will start to die in two to four days. Perennials may take up to 10 days to die off. The reaction may be delayed if the weather is cold and cloudy.

Weed Prevention

The best way that you can keep weeds out of your vegetable garden is to stop them before they ever grow. Beyond what we’ve already discussed today, here are some other things you can do to prevent weeds.

  • After you have planted and mulched your garden, you should be careful not to disturb the soil as much as possible. The truth is, weed seeds can remain dormant in the ground for years. When you cultivate your garden, you can uncover these dormant seeds, and before you know it, you have weeds growing. Try to use no-till growing methods as much as you can.
  • If you decide not to use mulch, you should try to limit areas of bare soil. Don’t overcrowd them, but plant your vegetables close together enough to cover the spaces where weeds can grow.
  • Because some crops can offer natural weed control, you should use crop rotation in your garden.
  • Throw away the weeds after you pull them. If you leave them lying around, they can retake root and start to regrow. This is especially a problem in wet weather.
  • Planting cover crops like buckwheat or winter rye can prevent weed growth. They contain organic growth inhibitors that can suppress certain weeds through the release of natural toxins.
  • You can use a stirrup hoe to dig up weeds. Do it when the plants are young. And leave the soil as undisturbed as possible, so you don’t uncover dormant weed seeds.
  • If you have substantial weeds, pull them out by hand. Be sure that you pull out the entire plant, including the root. This process is much easier when the soil is wet.

The Bottom Line

If you want to keep the weeds out of your vegetable garden, it’s crucial that you not let them get out of hand. You have to put some work into it, but if you stay on top of it and kill or pull the weeds as soon as you see them, you will have a better shot at going weed-free.

Herbicides are an excellent option for killing weeds, but to keep them safe, you must read the label for directions. Mulching and pulling them by hand are the most reliable ways to get rid of weeds, but it’s a little more labor-intensive.

Good luck with whichever method you use.

Happy gardening!

Sources:

University of Nebraska-Lincoln

North Carolina State University

University of Maryland

Iowa State University

Cornell University

Cornell

University of Maryland

The University of Arizona

Georgia Tech

Mississippi State University

Utah State University

Michigan State University

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