What Are Biostimulants? Types, How They Work and How to Use Them

Biostimulants are one of the fastest-growing product groups in plant nutrition – and one of the most confusing. This guide explains what a biostimulant is (and is not), the main types, how they differ from fertilizers, and how to add them to a feeding program in a way that lets you see what they actually do.

What is a biostimulant?

In the EU, plant biostimulants are defined by what they do, not by what they are made of. The Fertilising Products Regulation (EU) 2019/1009 describes them as products that stimulate plant nutrition processes independently of their own nutrient content, with the aim of improving one or more of these characteristics:

• nutrient use efficiency;
• tolerance to abiotic stress, such as heat, drought or salinity;
• quality traits of the crop;
• availability of nutrients that are bound in the soil or root zone.

Biostimulant or fertilizer?

A fertilizer supplies nutrients. A biostimulant works on the processes around those nutrients – root growth, uptake, metabolism and the life in the root zone. That is why a biostimulant never replaces a base feed: without enough nitrogen, phosphorus, potassium and micronutrients, there is nothing for it to improve.

The main types of biostimulants

Biostimulants are usually split into two groups: microbial products, which contain living organisms, and non-microbial products, which contain substances.

• Humic and fulvic acids – organic substances used in the root zone, in mineral as well as organic programs.
• Seaweed extracts – extracts from brown seaweeds, applied to the root zone or as a foliar spray.
• Amino acids and protein hydrolysates – often used around transplanting, phase changes and other stress moments.
• Enzymes – used in substrates and recirculating systems, for example when substrate is reused.
• Mycorrhizal fungi and beneficial bacteria – microbial products that colonise the root zone, mostly used in soil and living-soil systems.

How to add biostimulants to a feeding program

1. Get the base right first. A stable base feed, EC and pH come before any additive.
2. Choose by goal. Decide what you want to improve – rooting, a stressful phase, the root zone – and pick the product type that fits.
3. Introduce one product at a time, at a fixed dose and in a fixed phase.
4. Record and compare with previous cycles, so you know what the product contributes before you add the next one.

Common mistakes

• Stacking several new products in one cycle – you cannot tell which one made the difference.
• Using microbial products together with oxidising cleaners or sterilising agents in the same tank.
• Expecting a biostimulant to correct a deficiency that is really a base-feed or pH problem.
• Buying products without a clear statement of what is in them and at what concentration.

Frequently asked questions

Are biostimulants always organic?

No. Many are of natural origin, but “biostimulant” describes a function, not an organic certification. Check the product documentation if you need inputs for an organic program.

Can I use biostimulants in hydro and coco?

Yes. Non-microbial products such as amino acids, seaweed extracts and humic/fulvic acids are widely used in hydro and coco. Microbial products are mostly used in soil and living-soil systems.

Is silicon a biostimulant?

Silicon is a beneficial element and is often discussed alongside biostimulants. Read more in Silicon for plants: how orthosilicic acid works.

Looking for a supplier? FertiQi develops and produces biostimulants in-house near Barcelona – for growers, distributors and private label brands. See biostimulants for professional growers and private label, or read our 6-step guide to a consistent cannabis feeding program.