Weed Control Tips – How to Kill Johnson Grass

Check out how to kill Johnson grass, the most annoying and nasty weed that can take over the landscape. This invasive weed rapidly colonizes the yard, usually found in disturbed sites, vegetable fields, ditch banks, roadsides, vineyards, and orchards.

You need to kill Johnson grass immediately before they can damage your crops even further.

Methods on How to Kill Johnson Grass

The best method on how to kill Johnson grass should be thorough. It should weaken and kill existing weeds and prevent the seeds’ production and spread, so they don’t grow back again.

Chemical Spray

For fast-acting methods of killing Johnson grass, you can use chemical options. Post-emergent herbicides and Glyphosphate are 2 standard options against this invasive weed.

Pros:

  • Fast-acting solution for killing weeds
  • Easy to use and apply
  • Widespread application ideal for heavy infestation

Cons:

  • Toxic to kids, pets, and other farm animals
  • Not environmentally friendly
  • Can poison the soil and kill other nearby plants

Glyphosphate-based herbicides work best in getting rid of widespread and dense clusters of this weed. Compare-N-Save Weed Killer is 41% Glyphosphate, an effective solution against Johnson grass. It’s a potent weed killer than can deliver impressive results in two to four days.

One of its best features is this weed killer becomes waterproof two hours after application, so there is no issue if it rains. This 1-gallon concentrate, once diluted in 85 gallons of water, cover up to 25,000 square feet, suitable for large infestations.

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  • Rainproof in 2 hours
  • Visible results in as little as 2 to 4 days
  • Contains 41-percent glyphosate

You can apply this weed killer in driveways, paths, patios, fences, and around trees, shrubs, and flower beds. The best time to use this product is during the day, with around 60 degrees Fahrenheit.

This weed killer is an effective way to kill Johnson grass in the yard. It doesn’t only dry out the leave but goes straight to the roots and destroy it too.

The only downside is it can also kill all types of plants. You have to be careful not to spray this solution to those you want to preserve.

Weed Control Tips – How to Kill Johnson Grass

Organic Approaches

Killing Johnson grass doesn’t necessarily mean you need to introduce harmful chemicals that can poison the soil and kill nearby plants. There are organic approaches that are also effective in getting rid of Johnson grass in your yard.

Spray Without Chemicals

You can get rid of the pesky Johnson grass from your yard using only the simplest ingredient from your kitchen, like white vinegar. The acetic acid in vinegar is potent and effective in burning the weed. It is also an inexpensive option compared to chemical solutions.

When choosing a vinegar for killing Johnson grass, check out the percentage of acid it contains. Choose one that has the highest acetic acid concentration for better and faster results.

You don’t need to dilute the vinegar in water. Spray it directly to the weed to kill it, making sure you pour in the root section as well. You may need to repeat the process every other day until the plants die.

The best time to apply vinegar to kill Johnson grass is during spring when the weeds are still young. You can also spray them with vinegar during fall when the rhizomes are building food reserves. However, make sure you don’t accidentally spray other plants when killing the weeds as it will kill them too.

Flood with Water

Flooding Johnson grass with around two inches of water can kill the underlying rhizome of the plants, which is an effective way to get rid of it. Make sure to maintain the high water level in the infested area for at least a month to thoroughly drown the plant.

This eradication technique is useful, but only for yards that get conveniently flooded.

Physically Remove Grass

Hand pulling individual plants is one of the most effective ways to kill Johnson grass. However, you need to be thorough when doing this method. Aside from the stems, you have to pull out the rhizomes as well. Otherwise, it can grow back and infest the yard again.

The best time to physically remove the Johnson grass is in spring when the soil is still moist. This way, the plant will slide out the ground without issue, and there is less chance that the rhizome breaks.

Hand pulling individual Johnson grass is time-consuming and only suitable for light infestation.

Newspaper Mulch

Another way to get rid of Johnson grass in the yard is by mulching the infested area with newspaper. After mowing the lawn, covering the ground with paper will prevent the weed from getting air, water, and sunlight. Without nutrition, the unwanted Johnson grass couldn’t thrive and will eventually die.

You can expect to see results in 2 to 4 weeks when using this method. However, ensure that you put weights on top of the newspaper mulch so it won’t get blown away. There is also no need to take the paper away after weeks as well as it will decompose.

Tips and Warnings on How to Kill Johnson Grass

  • When using Glyphosphate-based herbicides, make sure you wear protective gear such as eye goggles and gloves.
  • Most herbicides are non-selective, which means they can kill all vegetation that it touches. Be careful in getting the chemicals on plants that you want to preserve. You can cover them with a tarp if they are near the infested area to protect them from the chemical residue.
  • Check your lawn carefully if there are Johnson grass growing. Pluck them out immediately to avoid spreading into other areas.
  • Wear protective gloves when removing Johnson grass by hand.
  • Kill the weed before it starts generating seeds. It won’t be easy to get rid of them if the seed head can fly into the air. The Johnson grass usually starts developing seeds in between May and June.
  • Regularly mowing the infested area can weaken the Johnson grass and kill them eventually. However, it is a long-term method of getting rid of the weed, instead of showing quick results.
  • Spray post-emergence herbicide on your growing garden. It’s an effective way of preventing Johnson grass from growing in the area.
Weed Control Tips – How to Kill Johnson Grass

Conclusion

The Johnson grass is a rapidly growing weed that can infest your yard in no time. It is incredibly invasive when not controlled and can decrease crop production. Keep your lawn free from pesky weeds with the most effective way on how to kill Johnson grass.

Last update on 2020-10-28 / Affiliate links / Images from Amazon Product Advertising API

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Jill Sandy

Jill Sandy

Jill is a sustainable focus gardener. She loves decorating her home backyard with beautiful landscape design and creative garden care techniques she develops herself. You can reach her at jill@constantdelights.org

Chanh Ho (MD, MPH)

Chanh Ho (MD, MPH)

Chanh is our Head of Medical Review. He is a research physician at Oxford University Clinical Research Unit. After accomplishing the program of level 1 sub-specialty in Pediatrics, he was awarded the Chevening Scholarship for his Master’s degree of Public Health in the University of Edinburgh in 2019

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