Thanks for the pics and experience. When doing comparisons, it is good to remember that vinegar is a contact killer, and does not act systemically as Roundup does. 5% vinegar typically will not kill the roots of perennial weeds. From the scientific trials I have seen, 5% vinegar also shows a great deal of variability between weeds, with some young weeds not well controlled.

Here is a link that might be useful: WSU article

Hotter temps are not better. At high temps liquids dry quickly. Couple that with low humidity and lots of sun and you have virtually instant evaporation. Better spraying at under 85 degrees. The early morning and early evening are better in my experience.

That first weed looks exactly like what is trying to take over my zone 7 bermuda lawn. Do you know exactly what it is and how to destroy it. The vinegar would be good in small sections but I have a bunch of it. I would be killing alot of lawn using it. I'm thinking it's crabgrass and should maybe use MSMA. Any thoughts?? Thanks.

Jodonne
Maybe it's dallisgrass... something like that. MSMA will definitely kill it. Keep in mind the "A" in MSMA stands for arsenic so be careful as you would any chemical herbicide.

Even though vinegar will only burn the leaves of the weeds and doesn't travel down to the root like Round Up does, I would think that repeated applications of vinegar would evenutally kill the plant by smothering it.

Todd, it may with some but does not with deep seated perennials that reproduce like Canada thistle and othets with strong rootbuds. The problem with many of the studies available (or at least the ones that I've seen) is that they do no follow up over the course of a few years-only that season. Wiith canada thistle in my yard the population of a few plants more than doubled from one year to the next using 5% vinegar for control. No, not scientific just my (alarming) observation.