How long does weed killer take to work?

You will usually see the weeds start to yellow and wilt within 7 to 14 days, and die off fully in about 2 to 4 weeks. Tougher, well-established weeds can take the full four weeks, so it is worth being patient rather than expecting them to drop overnight.

The reason it is not instant is also the reason it lasts. The treatment has to be drawn in through the leaves and carried down into the root before the weed dies from the inside out. A weed that looks a bit sorry after a few days is a good sign, not a slow one, it means the spray is working its way down. If something wilts within hours, that is usually just heat or damage to the leaf, not the root dying.

So the honest timeline is: a few days of no obvious change, then yellowing and drooping through the second week, then browning off and dying back over weeks three and four. Once they are dead you can brush or wash the dead growth away and the paving stays clear far longer than it would after pulling or burning.

Because of that timescale, my guarantee runs to four weeks: if the weeds on the area I have treated have not visibly died within four weeks of spraying, tell me and I will come back and re-spray that area free. I cover driveways, paths, patios and gravel across Leicestershire.

Ready for a price? Send a photo of your weeds and I’ll text you a fixed price within 24 hours.