Residents in York are being encouraged to form a "bucket brigade" to save the city's trees - by watering them with dirty bath water.
The council said record temperatures in July has caused serious concerns for the health of the city's trees, many of which are in danger of dying.
The public have been asked to throw the water from their baths onto trees in their gardens and in nearby streets.
The council plants between 400 and 500 trees in York each year.
Council spokesman Harvey Lowson said: "You can never over-water a tree and bath water is perfectly useable.
"Take some outside and put it on a nearby tree if you can. Something is better than nothing."