For those of us with those pesky dandelions, I read about a way to get them. This is supposed to work on most weeds, but I have only tried it on dandelions. Distilled white vinegar. About $4.00 for a large jug. This should be used for spot treating as the vinegar may harm your grass or plants. I used it on some dandelions in the grass and if the dandelion is large enough it and you're careful it's fine. Within 1 day they were shriveled and dried up. No harm to the pets, kids or environment.
Vinegar is a decent herbicide, it also works best if you use it on a sunny day. But it's a broad spectrum herbicide and it will kill desirable plants as well as weeds so you do need to be careful not to get it on anything you want to keep. With some weeds you need to hit them with vinegar a few times before they'll be totally dead, and for some of the tougher things it may not work as well.
And I will try it on the Mares Tail that has been introduced to my herbaceous border, it is such a tough plant to kill and as it is in among other plants, I will dab it on in a still day, let you know how it works for me, good luck and thanks. WeeNel.
In an effort to find out about replanting an area sprayed w/ vinegar, I discovered the following: That food grade vinegar you buy at the store is about 5% acetic acid, but it takes higher concentrations to kill most weeds; and that it only kills the top growth, so it's ineffective on perennial weeds.