Answer: You will need a day or two of dry weather before you can spray a weed killer. If you use a vegetation killer such as Round Up, the effect is almost immediate (24 hours) so arrange your application so there will be at least 24 hours of dry weather. Once the weeds are dead you'll want to pull them out. An alternative is to flame the weeds with a propane torch - not enough to set them on fire but just enough to overheat them so the water within the tissues expands and explodes. This will kill the weeds.
Best wishes with your garden!
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