Weeds are a lot easier to kill than you may think, like flies and cockroaches.
In just the same way that many things other than insecticides will kill pests, many things other than herbicides will kill weeds.
The reason is not too hard to understand – weeds, and any plant for that matter – are carbohydrates. As well as that, they have vesicles and cells that are dependent upon delicate ionic and pH balances.
If you use glyphosate or other systemic herbicides, it takes the best part of a week for it to start working, which is often perceived as being too long.
So go into your cleaning cupboard and see what you’ve got. Any cleaner is usually alkaline or acidic, and most of them will work. What do you have – Ajax Spray & Wipe with lactic acid? That’ll do. Bam Easy Off with sulphamic acid? Yep. An oven cleaner (caustic or non-caustic)? Sure thing.
Any of these things will do the job. The only difference between these cleaning chemicals and the herbicides is the amount you will need to use – with a herbicide a light misting on the leaves will kill the plant, whereas with a cleaning chemical a more significant dousing will be required.
An excellent option that is now being used in some products (along with a herbicide) is acetic acid (vinegar). Get yourself a 5L garden sprayer, tip in a cheap bottle of vinegar, top it up, and give your weeds a dousing, and the weed will curl up and die in a day or two.
Or if you want to do it quicker, use either an oven cleaner, or hydrochloric acid (1:10 will do it).
Btw, I’m not a great fan of glyphosate (roundup, zero). It’s not strong enough. A far more potent product are the once-a-year weeders