The Roundup concentrate weedkiller is for use on unwanted vegetation and areas such as hard surfaces including drives, patios, paths, tarmac, gravel and paving not intended to bear vegetation. Always apply roundup between May and September to an actively growing lawn before the onset of dormancy. The solution gets degraded into the soil by the microorganisms, killing the roots so, weeds don't come back and removing dying and dead lawns. The liquid usually takes 7 to 10 days to translocate to the roots of the treated lawn. Size: 280ml.