Trees are being protected by wool in a pioneering project to end the plague of plastic in new woodlands.
A national scheme to test alternatives to plastic "tree guards", used to protect saplings from animals and the elements, is trialling six different methods including waterproof cardboard and a polymer made from bacteria, as well as a wool and cashew nut material.
Industry non-profit the Forest Canopy Foundation is installing 870 of the tubes at 10 planting sites across the UK this year.
Currently plastic tubes are widely used in tree-planting schemes, with millions thought to have been installed over the past few decades.
Tender saplings must be protected from being eaten by Britain's growing deer population, and the protective sheath also acts as a greenhouse shielding the plant from harsh weather.
But the plastic tubes are often not removed once the tree is grown and can remain in woodlands for years, leaving waste in the countryside which can break down into potentially harmful microplastics.
The current push for tree-planting has led to fears of a rise in plastic use, undermining the environmental goals of forest creation.
Ahead of the 2019 election the Conservative party pledged to plant 30m trees each year by 2025. The wool and cashew nut formula, created by UK company NexGen in partnership with Italian scientists, uses a cutting-edge formula never before used in any material.
Wool fibres are held together with a resin made from castor oil and cashew nut shell liquid, designed to break down over five to ten years as the tree grows.
Founder Gary Hurlstone's father Graham invented the original plastic tree sheath in the 1980s. The company uses wool bought from 1,200 UK sheep farmers and cashew nut shells left over from the food industry.
Mr Hurlstone said: "The plan is to eradicate the use of single-use plastic in forestry within five years. We've got a way to go, we've got to get them into production, but we think we can get there."
Ed Bradbury, who is coordinating the project at the Forest Canopy Foundation, said the hope was that the guards would last for five to seven years and break down after that point, meaning they don't need to be collected, cutting costs.
Testing sites include the Caradoc Estate near Ross-on-Wye in Herefordshire and Barningham in North Yorkshire.
"We're hoping to test sites with a variety of conditions, some wetter sites, and sites that will be fenced and protected. Different strengths of wind, different exposure, different saplings," he said.
The project is being monitored by certification scheme Grown in Britain and has been funded by construction company Morgan Sindall.