Question about Killing "Johnson Grass"

[TransplantedTexan]

Hi All! What a cool site! I am new to organic gardening (and pretty much gardening in general) and going into my second year with a vegetable garden. I am having a problem with "Johnson Grass" invading my garden and don't know what to do about it. So far, I have been digging all new shoots and any old roots that I find and disposing of them, but I am afraid I am not going to be able to keep up with this method as my garden is fairly good size. Any ideas? Someone told me I could plant sunflowers wherever Johnson grass is and it would kill it....but my source was not sure about that!

Thanks for any input!

By the way, I am not sure Johnson Grass is the correct name for the stuff...that is the name my 95 year old grandmother calls it.

[Gary350]

I'm not sure what Johnson grass is, is it what some people call wire grass?

I have a problem with wire grass I water it with salt water and it kills it. This works good in July and August when it is hot and not much rain. I don't want to put any poison near my garden so I buy 50 bags of salt at Tractor Supply store for $4.50 per bags. A bag of salt mixed in a 30 gallon trash can of water works great for me. I use to have several spots of wire grass in my yard now I only have 2 places with wire grass.

About 1/2 my back yard is wire grass I have been tilling a 3 ft wide strip all the way around my garden to keep out the wire grass. This may be the year I kill that stuff for good. I might just till my back yard once a week until August it should be dead by then. I have a young tree in the center of the wire grass the salt water might kill it too so tilling is probably best.

[webmaster]

Putting salt in your soil is not recommended. Never do that. The salt will remain in the soil and keep killing anything that tries to grow.

[Gary350]

Putting salt in your soil is not recommended. Never do that. The salt will remain in the soil and keep killing anything that tries to grow.

I have to disagree with that. Salt will not remain in the ground very long. Every rain will wash more and more if it away until it is completely gone. It is typically considered that salt in the ground is 100% strength, after the first rain it is then considered to be 50% strength, after the 2nd rain it is 25% strength, after the 3rd rain it is 12.5% after the 4th rain 6.25%, after the 5th rain 3.1%, after 6th rain 1.5%, 7th rain .78%, 8th rain .4%, 9th rain .2%, 10th rain .1%. The salt is 99.9% gone after 10 rains, with evening showers in the summer the salt will be gone in a few weeks in TN where I live now and in Illinois where I use to live.

I know for a fact from experience that salt will kill the plant that you put it on and 30 days later new grass is coming up in the dead spot and in another month you can not find the dead spot.

One more interesting note, I don't remember the chemistry term for this but we learned this in chemistry class in high school. If you put 1/2 inch of salt in a glass then carefully fill the glass with water the crystal salt remains in the bottom of the glass. After 24 hours the crystal salt disolves into the water without stiring. The high concertration of salt in 1 spots tries to become more neutral so it spreads itself through out the entire container of water. Now you pour that glass of water into a larger container and dump in an equal volume of ice. When the ice melts you can see the seperation between the pure water and the salt water but tomorrow it will all be 1 mixture again the salt tries to become less concentrated in 1 spot and spreads it self through out the entire container of water. Salt does the same thing in the ground. You pour a cup of salt on the ground and in 2 months you can not tell salt was ever there. Naturally this will not work if you pour salt on rock or in the desert where it never rains. Research shows that salts goes down very deep in the soil.

One more fact. In the north the highway department puts several tons of salt on the roads in the winter. If salt did not go away all by itself then there would be no plant live anywhere near any highway, road or street.

[The Helpful Gardener]

Salt kills soil biology and can make life hard for any plant coming in after it. In calcerous soils the salt will lock up much faster but we have acidic soils that don't have much forgiveness about salt. I have used it in greenhouses, to knock down weeds under benches, but I do not use it outside and recommend burn down products like acetic acids to do that...


And diffusion helps a lot, but you can make that argument for any kind of pollution. That said, salt is naturally occuring and not toxic, and if it was a real invasive issue I might consider it. But I would try lesser evils first...
HG

[rtruitt]

I too have struggled with this plant as it propagates itself with both seeds and rhizomes underground.

I too use hand methods but sometimes get way behind.

I would try 20% vinegar to kill the tops. It will have to be used again a few times because the roots will resprout leaves but it should work. You might also consider orange oil. It will also kill the tops but I am not sure about the roots.

Location of the Johnson will be the determinant of what you use. If it is real close to garden plants you want to keep you will need to be very careful or not use sprayed vinegar or orange oil and concentrate on the hand methods.

Applying compost to your garden will loosen the soil over time and make hand methods easier.

No perfect answer I know but that's how it goes. I wish they had kept Johnson grass in Africa where it came from. It was imported as an animal pasture grass and became a pest.

Good luck with that garden!

[The Helpful Gardener]

True Ron, a lot of stuff came this way with human plans and figerprints all over it; we pollute with plants far too often...

We have a giant knotweed around here that most folks call Japanese bamboo, brought over as cattle feed. Nobody asked the cows; they hate it. It is a horrible clonal invasive that also throws seed to boot.

Interestingly it can be eaten by humans; perhaps we should be cleaning up our messes by cleaning our plates...?

HG

[!potatoes!]

works for dandelions.

[The Helpful Gardener]

Yep, twenty bucks a pound at the Union Square Farmers Market for dandelions and me with a yard full of organic crop... hmmm...

HG