British researchers have identified a genetic trait that causes willow trees to yield five times more biofuel if they grow diagonally, compared with those that are allowed to grow naturally up towards the sky.

Scientists led by Dr Nicholas Brereton and Dr Michael Ray, both from the Imperial College London, found that when willows grow at an angle, such as when they are bent by strong winds, they produce high-energy sugar molecules in an attempt to strengthen their stems and straighten the plant upwards.

These high-energy sugars can be fermented into biofuels when the trees are harvested, although the process needs to be more efficient before it can rival fossil fuels.

Willow is already cultivated widely across the UK for biofuel for motor vehicles, heating systems and industry. The researchers say that in the future all willow crops could be bred for the genetic trait to produce the extra sugars and be a more productive and greener energy source.