I guess that whether or not the roots of a given weed will be killed by surface methods...depends on the size of the weed, how vigorous/deep the roots are, and how often a person repeats the surface treatment. My boiling water 'treatment' of weeds growing between my pavers next to my short driveway, only took one application. Seedlings show up each spring, but that's to be expected. I'm wondering if the steam treatment, if held over the larger weeds for a length of time, would 'cook' the roots and actually kill the entire plant? Or follow up treatment of any plants that didn't DIE, DIE, DIE, YOU WICKED WEED with the first steam treatment. I would be inclined to test this method out before resorting to salt or even the less invasive method of dragging the driveway.

Many weedy Lactuca grow quite tall. Scroll half way down the page in the link below. Look over the species from the USDA database which include your area. Search for images on the species listed. You may find a match. Here is a link that might be useful: Lactuca

Looks like a form of Amaranthus cruentus. Weedy but edible. Joe

Eric, that cultivar of Phytolacca americana is quite striking. I wonder if it would seed true? Pokeweed is one of the weediest plants on my lot, and one of the few wild natives that competes effectively with the exotic invasives. The same suspects that NHbabs deals with - buckthorn, oriental bittersweet, Rosa multiflora, etc. One other "worst weedy" is the species Eupatorium rugosum which I started from seed. If you think the chocolate version is weedy, you should see the regular green version. Rampant grower and seeder in shade or drought, and none of the critters eat it. At least it's native and the flowers are pretty, and the bumblebees love them.