A word of introduction
Biostimulants are products used in agriculture for various purposes: increasing yields, crop quality and other aspects such as physical traits (color, sugar content etc.). In contrast to biopesticides, biostimulants do not act directly against pests or diseases, but they improve the plant's vigour when faced with biotic or abiotic stress. Biostimulants help plant growth by acting, for instance, on nutrient availability in the soil. Plant biostimulants are as diverse as their purposes and include products made of algae, micro-organisms, proteins etc.
The applicable legislation for biostimulants in the EU is either the pesticides or the fertiliser legislation, depending on use, composition and label claims. Indeed, the line between what is considered being a PPP or a fertiliser is very thin for some products. Some biostimulants, for instance, would be considered being plant growth regulators which are regulated under the Plant Protection Regulation 1107/2009.
To date, and until the updated European Fertiliser Regulation enters into force biostimulants are regulated by the national legislations in each country. Which is not what you would call a "harmonised" situation...as you will see from the information below :