Hi Linda,

Thank you for your question about using other agents such as vinegar, dawn soap and salt for weedkiller. This is a common question we get about using natural or home products for weed management. The answer is that it depends on what, how much and when you apply it. 

There is herbicidal vinegar on the market with a concertation of 20% that is effective against broadleaf weeds. But it can be toxic to handle. Our everyday kitchen vinegar is at a concentration of 5%. So pretty diluted compared to the true herbicidal vinegar.

The University of Maryland Extension has an in-depth article, Vinegar: An Alternative to Glyphosate? This was shared in a previous Ask Extension question. 

The idea of using Dawn soap or any liquid dishwashing soap is to act as a surfactant which means a sticky substance that can hold water against a surface (the vinegar against the plant tissue). Yes a dish soap can work as a surfactant but its not the best surfactant. There are surfactants on the market for herbicidal use.

Finally, salt can be used to kill weeds but directly applying it to small plant better in solution. Table salt is usually sodium chloride and Epsom salt is magnesium sulfate. Epsom salt or magnesium sulfate can be used in small quantities as a fertilizer to add magnesium to the soil.

Table salt or sodium chloride can help kill weeds but to use enough of it to kill weeds effectively, it will actually cause more harm to the soil than its ability to kill weeds. It will kill the worms and beneficial insects. it can kill your trees. So be cautious with using large amounts of salt.

So if you have young weeds with only 1-2 leaves in walkways or driveways I would say go for it and use the vinegar, dish soap and salt to kill the weeds. But if they are near plants and trees you care about, please don't use these agents. 

Instead, consider pulling them out by hand and mulching the area for weed suppression. 

I hope that I answered your question. Don't hesitate to ask additional questions.

Sincerely,

You are welcome