It does need to be the glyphosate version of roundup, or any other brand. It's getting harder to find and I believe it's banned in some countries. A lot of the easily available weedkillers are based on things like acetic acid (AKA ethanoic acid,vinegar) or pelargonic acid (AKA nonanoic acid, similar molecular structure to acetic acid but with a much longer carbon chain) which don't act systemically, they just kill off the green top growth. That might be enough to finish off small annual weeds or seedlings that don't have much of a root system yet, but it will do nothing much for more established weeds with bigger roots - they'll grow back. And I'm not convinced that beneficial soil organisms wouldn't be harmed.
I think many of us on here only turn to weedkillers where the weed roots are somewhere we can't get at to dig out or hoe off, like under a path or wall, and we wouldn't bother for little seedlings and annual weeds that are easy to pull out or hoe off, so the acetic/pelargonic acid weedkillers wouldn't be of any use. One of these days when I'm somewhere that sells that kind of thing I'll have a look at the packaging to see exactly what they claim, but I'm betting they gloss over the fact that they're just a "chemical hoe". It would be a lot cheaper and just as effective to keep cutting off the top growth every time it grows back.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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