Whether you have used herbicides to kill the weeds and they haven't worked or you don't want to spray harsh, pollutant chemicals, you can try burning your weeds with a propane torch. Torches do not work as well on lawns and might actually harm your grass, but if herbicides do not work, a torch will. Typically, torches are used to burn weeds that are growing up between sidewalk cracks, in the roads and in driveways where they are surrounded by asphalt, rock or concrete instead of grass, bushes or other vegetation. Propane torches heat the cells causing them to expand and burst, killing the weeds.
Contact the fire brigade before burning any weeds. Ask the department if weather conditions are favourable for burning your weeds. Listen to the firefighters' advice and follow their instructions carefully. Obtain a burn permit from the fire brigade if one is needed.
Carry the propane and torch in a safety case to the location where you will be burning weeds.
Load your backpack so that the pressure valve is pointing away from you if you are using a torch that requires a backpack. Keep your backpack or propane tank away from the flame.
Ignite the propane torch with a flint lighter. The torch heats quickly, so don't lay the torch down.
Steady the torch about six to 12 inches above the weed. Walk slowly as you swish the torch from side to side so that it overlaps.
Burn the plant until it begins to wilt. This is enough to kill the weed. If you hold the fire over the weed until it catches on fire, this stimulates root growth. Focus your burn on the stem base.
Search for wilting 24 hours after you burn the weeds. Burn the weeds the rest of the way once they are dried out and dead. This might be one or two days after your first burn.
Allow your torch to cool down completely before you disconnect and store it.
Repeat the treatment the next season.
Wear leather gloves, face shields and hard hats when using torches. Bring a first aid kit to the site with you in case you get burnt. Work with someone who can watch for fires and monitor your progress.
Do not use fire to burn your weeds during drought or burn bans, because it is dangerous.