WASHINGTON, Monday 12 July 2010 (AFP) - Residents of the leafy US capital were delivered an unusual request Friday as the city sweltered under a prolonged heatwave: please water our trees.

A statement from the forestry administration said it was "launching an effort to engage as many residents as possible in watering street trees so they survive this hot summer."

Temperatures have soared along the East Coast in the past days, creeping above 100 degrees Fahrenheit (37 degrees Celsius) and cloaking the city's tree-lined streets in a stifling early summer heatwave.

"Summer heat and normal urban pressures create intense stress for street trees," said chief forester for the District of Columbia, John Thomas, who keeps a close eye on the 140,000 trees that flourish in Washington.

"We are calling on district residents and businesses to help water street trees close to their homes and offices."

Residents have been asked to sign up to take care of one or several trees during the hot summer season, becoming an official "canopy keeper" and receiving a free "watering device."

The drip device fits around the tree trunk and is filled up once a week, emptying slowly at the foot of the tree.

"We are getting the word out to people that we need their help. Because of the weather, trees are really in danger," spokesman for the city authorities, John Lisle, told AFP.