Ethylenediurea (EDU) is a chemical which protects plants against O3-induced stress.
It is unclear if EDU is toxic to terrestrial plants or if it acts as N fertilizer.
We exposed willow plants to an ambient O3 level and high chronic doses of EDU.
EDU did not cause toxicity to plants and increased the N content of leaves.
We estimated that low EDU doses do not act as N fertilizer.