As stated above roundup, or the equivilent is gallup 360, both glyphosphate based weedkillers, they will need a couple of hours dry weather,
scutchout 360, or weedfree 360 is the exact same thing.
All these products kill from the root back so it will be about a week to 2 weeks before you see the weeds dying,
2 to 3 sprays a year should see you right,
If bramble type weeds, try garlon, scrubkiller, grazon 90.
hope this helps...
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