If it is the Path Clear type which contains sodium chlorate then at least three months, possibly even 6 months to be certain. If the bed is empty of all plants then you are wasting money putting Roundup type weedkiller as it needs to be absorbed by green leaves to work.

Thank you for your help. I'll give hard work a go :)

Don't use weedkiller, ever thought of the insects & wildlife?

All weeds are a part of nature, they grow for a reason.

If you must destroy them, remove by hand and compost them. :)

I would take issue with Dongdong on this point. There are a fair number of plants which should not be put on a compost heap, if only because the heat generated in a domestic type pile is just not enough to kill off the roots. Anything diseased or with really persistent roots should be disposed of either to the Council waste or by burning. And there are, sadly, many weeds which no amount of digging and removal by hand will ever clear. We have ground elder and couch grass in the roadside border coming in from the road verges. The only way we can even keep it under some semblance of control is with weed killer. You take your pick, you either have a garden full of the plants YOU want to grow or you have one where there are plants which grow where THEY want to. And let's face it a garden is a highly artificial thing.

When you study Ecology, anthropology, Ethnobiology ethnobotany, Ethnomycology and numerous other subjects you will see that nature does best when left alone.

Here are just a small number of extremely dangerous substances found in weed killers, Glyphosate Isopropylamine,Tallow alkylamine ethoxylate, Goal (oxyfluorfen), Gramoxone Inteon (paraquat), Weedtrine-D (diquat). phenoxy and pyridinoxy-phenoxy , dinitroaniline and miscellaneous others.

All of the above ARE 'Toxic to aquatic organisms' or organic life forms.
Anybody with half a brain would know that also means humans.

I can see where you are coming from Owdboggy, but lets think on a larger scale and in holistic manner.

Now I wonder how many tons of this poison is poured into the soil each day, most of which ends up leeched into our children's and our own drinking water.
Not to mention the devastating effects it has on the natural environment, insects and wildlife.

To round it up, personally I would rather choose to sacrifice the occasional hard work to remove anything unwanted, than to contribute towards the destruction of the planet for something that simply looks artificially, 'Neat & tidy'

No offence, just my view. :)

I agree with your main point, but still stick to mine, that there are some plants which have to be controlled chemically in the highly artificial environment of a garden.
Try getting rid of Japanese knotweed any other way! Even the bug they are introducing from Japan that eats it, will only reduce the problem, not remove it.
With native plants it is a different matter, those we live with, but so many things have been brought in which have proven to be 'thugs'. Ground elder is not native, Bindweed is not native, Russian Vine is not native, Policeman,s Helmet is not native and there are plenty more of these alien invaders which are causing far more damage to our native plants than the chemicals used to control them.
Mind I do agree that the indiscriminate spraying of chemicals on the land is not a good thing. There needs to be the careful (and I stress, careful) use of weed killers. On the occasions when I use Glyphosate, I am careful not to allow it to touch the soil for example.
Oh and yes I have studied most of the subjects mentioned and in a perfect world there would be no need for human intervention, but it is not a perfect world.
My original comment was not in anyway meant as an attack on you by the way, only a statement of my slightly differing opinion.
And now I am off out to dig up some more of the thousands of Allium farreri seedlings which are infesting my Crevice garden and which weedkiller does not touch, grrrr.

Oh dear, I only wanted to clear my little flower beds so that I can plant something in them later in the year. I now feel like a real eco criminal! Wait until I tell you about the ants!! ;)
Thank you for your comments, nonetheless.