Plant biostimulants are both regulated and defined in the European Union (EU).
The EU Fertilizing Products Regulation took effect in July 2019 and defines plant biostimulants as: "A product stimulating plant nutrition processes independently of the product’s nutrient content, with the sole aim of im proving one or more of the following characteristics of the plant or the plant rhizosphere:
- Nutrient use efficiency
- Tolerance to abiotic stress
- Quality traits
- Availability of confined nutrients in soil or rhizosphere."