If you're talking about a glyphosate-based weedkiller, you must leave the plants to die off - at least a couple of weeks - they need to continue to photosynthesise in order to pass the poison down to their roots and kill off the whole plant. If you don't leave the plants to die and go brown you run the risk of only killing the top growth and the roots will grow again.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
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Hi Greenegene
If you're talking about a glyphosate-based weedkiller, you must leave the plants to die off - at least a couple of weeks - they need to continue to photosynthesise in order to pass the poison down to their roots and kill off the whole plant. If you don't leave the plants to die and go brown you run the risk of only killing the top growth and the roots will grow again.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.