What are Plant Biostimulants and How to Use Them to Grow Cannabis?

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Added 26 October 2022

Plant biostimulants to grow cannabis? What in the world are they?

For hundreds of years, growers have been adding various fertilizers to improve their plant growth. The same goes for cannabis growers. But these fertilizers only go so far as to improve cannabis growth — they don’t fix the issue at the root; only provide a bandage fix.

But in the last decade, growers have started using a new kind of plant amendment — plant biostimulants — to grow cannabis and other plants. Plant biostimulants make the growing environment of the plant more suitable by enriching the growing medium with beneficial microbes and activity.

Biostimulants also reduce your dependence on fertilizers and nutrient boosters by ensuring your plant gets the most nutrients from its surroundings naturally. 

But what are biostimulants and how can you use them to grow cannabis? Find out the answers in this article. 

What are Plant Biostimulants?

What are biostimulants

Before getting into biostimulants for cannabis, let’s first understand what biostimulation is. 

Essentially, biostimulation is a process of gardening where the environment is modified by applying biostimulants around or on the plant. During this process, the biostimulants encourage bacterial activity in the area, leading to better bioremediation.

Now, what the heck is bioremediation? It is another process that is specific to bacteria and microbes in the plant’s environment, which include areas like soil, surface materials, and water. During bioremediation, the contaminants and pollutants are eliminated by natural bacteria present in the plant environment.

For these two processes to occur, growers use biostimulants — organisms or substances that eventually improve the cannabis plant’s growth and overall health. 

According to the Farm Bill (2018), biostimulants can be defined as the following:

“A substance or microorganism that, when applied to seeds, plants, or the rhizosphere, stimulates natural processes to enhance or benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, or crop quality and yield.”

Biostimulants is an umbrella term that includes various materials and organisms, not defined by their chemical makeup but by how they affect the plant’s growth. Such materials and organisms include bacteria, chemical elements, or plant extracts. More on this later.

Biostimulants for cannabis are quite new to the market — they are gaining popularity in recent years — but most of the biostimulant products’ efficacy is not proven and requires further testing. However, the growing interest is a mark of an important shift in how cannabis growers treat their plants. 

How Do Plant Biostimulants Work on Cannabis Plants?

How do biostimulants work

Biostimulants are best applied early in the growth of the plant, and they include various ingredients like plant extracts, beneficial bacteria, humic acid, etc. When done right, they can have various benefits for the plant, such as the following:

1. Improves Cannabis’ Tolerance to Water Stress

Cannabis is a thirsty plant, so it is prone to experiencing water stress due to common irrigation errors like underwatering, overwatering, or the water being harsh for the plant. 

In this case, biostimulants can be used to increase your plant's tolerance to water stress. 

For instance, when cannabis experiences underwatering, it can show symptoms like wilting. With the help of biostimulants, especially microbial-microstimulants like Pseudomonas bacteria, these symptoms can be delayed while also enhancing the plant’s ability to recover from such stress.

2. Increases Bioavailability of Nutrients to the Plant

When the cannabis plant is growing, it pulls most of the nutrients from the root zone, but considering how sensitive cannabis roots are to pH, nutrient uptake can be easily hampered by new growers. That’s one of the most common reasons for stunted or slow growth in cannabis plants.

Here, biostimulants can come in handy because they increase the bioavailability of nutrients in the medium, allowing the plant to absorb nutrients more efficiently. Even if the conditions are ideal for nutrient uptake, biostimulants can still benefit the plant tremendously.

3. Reduce Reliance on Fertilizers 

Not all fertilizers are good for your cannabis plant, and even the good ones can be potentially harmful to your plant if you don't use them the right way. In such cases, you can largely avoid the use of fertilizers by using biostimulants.

This benefit is akin to the one mentioned above. Biostimulants make various nutrients already in the root zone more available to your plant by boosting the microbial activity within the growing medium. This leads to your plant getting all the nutrients without largely requiring additional fertilizers

4. Makes Cannabis Resistant to Abiotic Stress

With the help of biostimulants, cannabis plants can better withstand abiotic stress. The biostimulants regulate the production of hormones that respond to stress, leading to enhanced production of auxins, cytokinins, and gibberellins (growth-promoting hormones), while also reducing the production of ethylene (stress hormone).

This not only enhances the plant's growth but also improves cannabis’ marketability since the buds can withstand stress experienced during the post-harvest process. 

5. Enhances Soil Fertility

If you are growing cannabis in soil, you know how crucial soil health is. The soil needs to be a lively ecosystem that can sustain the plant, which is easy to miss for many new growers, especially when using regular or low-quality soil.

So, growers can use biostimulants to promote organic activity within the soil medium, making it more friendly to beneficial microorganisms that further enhance plant growth by maintaining the soil environment.

6. More Sustainable Approach to Growing Cannabis

Of course, you want to grow cannabis without harming the local environment, but that can often be difficult considering the world we live in. It is almost impossible to be 100% eco-friendly in today’s world.

But biostimulants can get you one step closer to your goals. Most biostimulants are 100% safe for the environment and they don’t harm the local environment in any way. They improve the local soil’s fertility by promoting microbial activity within, which is a terrific benefit for not only your plants but also the plants that will grow there in the future. 

What are the Best Biostimulants for Cannabis?

Humic acid liquid

While there is a lack of official definition for plant biostimulant categorization — because there are just so many sources of plant biostimulants — there are a few that are popular in the cannabis-growing community. Here are some of the best common plant biostimulants for cannabis plants.

1. Beneficial Microorganisms

Your plant’s soil is not lifeless. It is a rich ecosystem of various organisms working together to provide your plant with metabolized nutrients. It is a diverse environment that benefits your plant’s growth.

So, by adding beneficial microorganisms to your plant’s soil, you can enhance the diversity within the medium, which improves the nutrient uptake of the plant. Plus, rich biodiversity in the soil can also enhance the plant’s tolerance to environmental stressors like heat or drought. 

Plant biostimulants that contain beneficial microbes are also known as microbial inoculants, and mostly, they contain bacteria, mycorrhizae, or fungi. You can add this type of biostimulant in the form of compost or worm castings. 

These products also make your garden more eco-friendly since such products are made with relatively small environmental impact while the supply can be theoretically infinite!

2. Humic and Fulvic Acids

The breakdown of organic matter within the soil produces humic and fulvic acids, but you can also add these acids in the form of organic matter, or liquid or granular amendments. 

These acids can help reduce your fertilizer application rates, so you don’t give your plant more fertilizer than is healthy. At the same time, these acids enhance nutrient uptake and metabolism in the plant and make the plant less prone to water stress. 

Additionally, humic acids also stimulate the growth of beneficial microbes within the soil that process the nutrients in a better way and make them available to your cannabis plant more efficiently, which would otherwise be unavailable to the plants. 

3. Seaweed Extracts

Seaweed has one terrific use in horticulture — it is rich in biostimulatory compounds like phytohormones and amino acids. For this very reason, seaweed extracts have been used by growers for decades. 

Research shows that seaweed extracts can significantly enhance the root zone and phyllosphere microbiomes, which improves soil quality, nutrition absorption rates, and even deterrence to pests and diseases. This can result in significantly higher yields during the harvest of cannabis.

Most seaweed extracts that you will find in your local gardening store are made from Phaeophyceae (brown algae), where the algae either goes through a heat extraction or chemical extraction. And you can apply these extracts either as foliar spray or directly into the soil. 

4. Protein Hydrolysates

Protein hydrolysates or PHs include compounds like carbon, amino acids, and peptides. This formulation makes PHs a terrific plant biostimulant that can benefit your cannabis plant in various ways, such as the following:

  • Encourage microbial growth in the medium
  • Increase the availability of various nutrients to the plant 
  • Builds plant resistance to biotic and abiotic stresses

Protein hydrolysates are manufactured using chemical or enzymatic hydrolysis of plant biomass and animal waste, and some of the common sources of PHs are fish byproducts, casein, blood meal, legume seeds, corn wet-milling byproducts, and alfalfa hay. 

While most PH products are animal-based, you can also find plant-based ones if you are particular about what kind of amendments to use on your cannabis plant. The latter is a more sustainable way of administering protein hydrolysates to cannabis and it is quickly gaining a lot of traction. 

In most local horticultural stores, you can find PH products in either liquid or powder form and these can be used as both foliar and soil applications. You can choose the one that suits your garden the best. 

5. Biopolymers

Biopolymers are another form of popular plant biostimulants that many growers use to grow cannabis. These products are made in various ways — plants, bacteria, animals, and fungi’s natural processes. Some of the common biopolymers include compounds like plant starches, gelatin, and collagen. 

Such biopolymers even have certain characteristics that give them an edge over other bio stimulants. For example, chitosan, which is derived from crustaceans shells, helps protect the plant against harmful fungal pathogens while also improving the plant’s resistance to cold temperatures, salinity, and drought. 

On the other hand, some biopolymers like sodium alginate can improve fertilizer uptake efficiency in places. This helps the plant absorb nutrients more efficiently while preventing symptoms of over-application or fertilizer runoff-related pollution problems.

6. Inorganic Compounds

The last type of common biostimulant for cannabis is inorganic compounds. These compounds are sometimes even the same micronutrients that cannabis requires to grow properly — they double as biostimulants!

Some of the most important inorganic biostimulants include aluminum, sodium, cobalt, selenium, silicone, etc. 

These inorganic compounds boost the microbial activity within the root zone, making the grow medium more suitable for your plant, and also give a boost of micronutrients to your plant. 

Do Fertilizers Work as Plant Biostimulants for Cannabis?

Do Fertilizers Work as Plant Biostimulants for Cannabis?

Fertilizers also help your cannabis plants grow bigger and sprout bushier buds, so doesn’t that mean it is also a plant biostimulant? Not really.

There is a major difference in how plant biostimulants and fertilizers function. Essentially, plant biostimulants don’t act directly on the plant but alter the microbial environment around the plant, like the rhizosphere and phyllosphere — areas where the plant interacts with its surrounding. Biostimulants make these environments more suitable for optimal plant growth.

On the other hand, fertilizers don’t largely alter the environment and make it more suitable. They simply provide certain nutrients that can help the plant grow bigger. Fertilizers are more direct in that regard.

Sure, some biostimulants do act like fertilizers in some contexts, but the nutrients must still be derived organically. Similarly, some fertilizers can also alter the surrounding environment if they contain biostimulants but this is a general distinction between the two.

How to Use Plant Biostimulants to Grow Cannabis?

How to Use Plant Biostimulants to Grow Cannabis?

Unlike fertilizers or boosters, biostimulants work to enhance the environment around your plant as opposed to boosting the nutrient levels for the plant to absorb. So, avoid thinking of biostimulants as fertilizers or boosters — they are more of an insurance. You only use biostimulants to prepare plants against stress so they can grow to their full potential. 

Depending on the type of biostimulant you use, you can mostly incorporate them into your preexisting cultural practices. However, each biostimulant product may have a different administration technique.

The most common form of administration for biostimulants is to either use it as a foliar spray or directly into the soil. Some biostimulants also come in granular form that can be incorporated into your growing medium during a transplant. Whichever biostimulant you choose, it is advisable to check the manufacturer's recommendations for the best results.

And considering the variety of biostimulants available on the market, you need to again follow the manufacturer's recommendation for dosing and other aspects of the administration. 

If you are still in the planning stage of growing cannabis, you can save the hassle and simply choose a growing medium with pre-incorporated microbial inoculants, which already contain beneficial microbes like mycorrhizae, so you don’t have to worry about biostimulants when growing the plant. 

When is the Best Time to Use Biostimulants for Cannabis?

When is the Best Time to Use Biostimulants for Cannabis?

The best time to use biostimulants for cannabis plants is as early as possible. This is because biostimulating products are most useful and effective when they are applied during the early stages of plant development. 

Applying biostimulants early allows the plant to grow healthy during the vegetative stage, which is the most important growth stage for the plant, while also making the plant capable of overcoming stress that it may face during its growth. 

Biostimulants also need time to work their magic, especially microbial inoculants, since they gradually alter the environment of the plant. So, don’t expect your plant to fight environmental stress just a day after applying biostimulants, give it more time. 

So, the best time to use biostimulants is as early as possible. You can apply biostimulants to grow cannabis when it is only a seedling or in the early vegetative stage to promote root development and plant growth. 

Depending on the type of biostimulant you use, you can also apply them during the final transplant of your cannabis plant into its final container. 

Remember that this is merely a general guideline and the best time to use biostimulants for cannabis depends on your local region’s climate, type of biostimulant you use, and your cannabis strain. So, refer to the manufacturer’s recommendations to know the right time for this.

You should also participate in local grower’s forums or here on our site so you can learn more about other growers’ experiences of using biostimulants on their plants and apply their learnings to your garden. 

Do a Test Run Before Using Biostimulants to Grow Cannabis

There are virtually hundreds of biostimulant products you can purchase to grow cannabis these days, but you should choose the right one for the best results. Otherwise, the results may turn out to be unsatisfactory. 

The first step in choosing the right biostimulant for the cannabis plant is to choose products that have undergone independent trials that back efficacy claims. 

The second step is to do a test run of the products regardless. You must carry out trials before implementing the biostimulant in your garden to ensure that the biostimulant works for your garden and does not waste your money and efforts.

This is because each cannabis garden is unique with its own sets of features and challenges. Some biostimulants may be more suitable for your garden than others. Doing test runs and trials allow you to double-check the efficacy of biostimulants without posing any direct threat to your cannabis garden. 

What is the Future of Plant Biostimulants for Growing Cannabis?

What is the Future of Plant Biostimulants for Growing Cannabis?

In recent years, climatic changes have become drastic in most parts of the world due to global warming. Drought, heat waves, and pollution have become quite common and each has the potential of hurting your cannabis plants’ growth and yield.

And some part of such changes is due to various agricultural practices that use synthetic fertilizers, leading to pollution and soil degradation.

While this may not affect cannabis growers as much as it would affect the farmers, we as growers must adopt the most sustainable techniques in growing cannabis to reduce our industry footprint as much as possible. 

And plant biostimulants are one way of doing that. They allow you to grow terrific yields while using fewer resources. Plus, they bring down your garden’s reliance on the use of fertilizers since they naturally improve nutrient bioavailability within the root zone while promoting water retention and root growth.

Biostimulants also go a long way in protecting your plant against abiotic stresses of drought and heat that are a result of recent climate changes as mentioned above.

Yes, a lot is still unknown about plant biostimulants — they are a relatively new type of plant amendment — but they are sure to play a major role in the coming years, not just for cannabis growers but for farmers around the world. They have the potential to make gardening and farming more sustainable and make plants more resilient.

Summary: What are Plant Biostimulants and How to Use Them to Grow Cannabis?

Traditional growers largely focus on improving the yield of their cannabis plants but don’t focus much on other aspects of plant growth like water, soil, and climate. The new rise of biostimulants is perhaps the next stepping stone to getting better at growing cannabis — this practice aims to balance yield with soil health, long-term resilience, and freshwater supplies.

Not only that, but plant biostimulants offer a lot more than just a new way of growing plants. 

For instance, biostimulants can improve plant growth significantly because they contain compounds that are essential for the natural processes of the plant. Biostimulants directly influence the microbes that promote plant growth and can be applied to seeds, shoots, and the root zone.

Additionally, biostimulants can also improve your cannabis plant’s yields. If you apply them properly, the organic alteration of the environment will lead to your plant growing bigger and healthier, which will further lead to better bud development. And better resistance to biotic and abiotic stresses will only aid the benefit. This will eventually lead to a much bigger yield that would have been difficult to achieve without plant biostimulants. 

Biostimulants promise a lot of benefits for your cannabis plant. So, consider using them on your cannabis plant and you will be rewarded with significantly better plant growth and higher yield. 



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Great Article very informative 😊