Guerilla knitters stormed Crystal Palace Park and ‘yarnbombed’ the trees to highlight the need for more young blood doners.

Inspired by the trend for yarnbombing, staff from NHS Blood and Transplant (NHSBT) hung woolly red blood drops from trees in the park to remind people blood does not grow on trees.

More than 100 blood drops were used to create the effect last Friday and people whose lives have been saved by blood donations came down to see the spectacle.

Croydon Guardian: More than 100 woollen blood drops were used to create the effect in Crystal Palace Park

NHSBT’s lead donor relations manager for London and South East, John Canning, said: “We’ve had a fantastic response to the campaign so far and enjoyed an incredible amount of support from knitters who created the blood drops for us.”

Yarnbombing is a type of street art which involves decorating prominent buildings and places with eye-catching knitted objects, often to raise awareness of an issue or promote a worthy cause.

Go to to register as a blood donor.