CSU Extension does not recommend using homemade mixtures of items found in home kitchens like epsom salts, vinegar and dishwashing liquid. There is simply no way to ensure quality-control with them.

There are herbicides that can be applied to gravel to eliminate weeds, however, because there are many different factors that need to be considered when choosing the best product for your situation, I recommend you contact Karim Gharbi, the Denver County Horticulture agent. His email address is <personal data hidden>.