Chitosan in Cannabis Cultivation: Resin, Terpenes, Roots and Natural Plant Defense

Chitosan is one of the most exciting natural active substances in modern plant cultivation. Nevertheless, the substance is still comparatively little known in cannabis cultivation.

This is also because chitosan is difficult to place in a familiar category.

It is not a conventional fertilizer. It does not provide the plant with large amounts of nitrogen, phosphorus or potassium. Nor is it an ordinary root stimulator or a simple contact agent against pests.

Chitosan primarily acts as a biological signal.

The plant recognizes certain structures of chitosan and responds to them. It activates defense mechanisms. It changes the composition of its root exudates. It produces certain enzymes and protective proteins. Specialized plant metabolism can also be influenced.

This area is particularly interesting for cannabis.

CannaSelection has been working with chitosan for several years. In our internal trials, we repeatedly observed a higher absolute resin quantity on treated flowers. The resin appeared more pronounced, and the plants’ aromatic expression was more intense and clearer.

This is explicitly not a claim that chitosan increases THC content.

It is about the quantity and quality of the resin produced. It is about the activity of the resin glands and the question of how well a plant fulfills its genetic potential.

Our results are internal practical observations. They were repeatedly observed over several years and across different applications. However, they are not a published field study. We therefore clearly distinguish in this article between published research, biologically plausible effects and our own observations.

What is chitosan?

Chitosan is a natural polysaccharide. It consists of long chains of linked sugar molecules.

The starting material is chitin.

Chitin is very common in nature. Among other things, it forms an important component of:

• crab and shrimp shells
• shells of other crustaceans
• the exoskeletons of insects
• the cell walls of various fungi

Chitin is a stable structural substance. Chemical or enzymatic processing removes some of its acetyl groups. This process is called deacetylation.

Chitin thereby becomes chitosan.

This is not an insignificant processing step. The properties of the material change considerably. Chitosan has free amino groups. These can become positively charged in an acidic environment. This makes chitosan more soluble and biologically reactive.

Chitosan is not ground crab shell powder

In the grow sector, chitosan is occasionally described as simple crab shell powder.

That is not technically correct.

Crab shells can serve as a raw material for production. However, in addition to chitin, they contain calcium compounds, proteins, pigments and other components.

These components are largely removed during production. The resulting chitin is then deacetylated. Only this process produces chitosan.

In simplified terms, conventional production proceeds as follows:

1. Crushing and cleaning the raw material
2. Removal of minerals
3. Removal of proteins
4. Removal of pigments and residual substances
5. Obtaining the chitin
6. Deacetylation of the chitin
7. Purification and drying of the chitosan

The finished chitosan is therefore a processed biopolymer. It must not be equated with ground shells or chitin meal.

What raw materials can be used to produce chitosan?

Most commercial chitosan products are produced from by-products of crustacean processing.

Typical sources include:

• crab shells
• shrimp shells
• crayfish shells
• other marine crustaceans

These raw materials are generated in large quantities during food processing. Instead of being discarded, they can be used to produce chitin and chitosan.

Chitosan from fungi

Chitosan can also be obtained from fungal biomass.

Fungal cell walls contain chitin. Some fungal groups also already contain a certain proportion of chitosan. Production from fungi can take place under controlled conditions and is less dependent on seasonal fluctuations in marine raw materials.

Fungal chitosan is also of interest for applications where animal-derived starting materials are deliberately to be avoided.

Nevertheless, fungal chitosan is not automatically better than chitosan from crustaceans. The actual product properties are decisive. These include purity, molecular weight, degree of deacetylation and solubility.

Chitosan from insects

Insects also contain chitin.

Therefore, by-products from insect farming can in principle also serve as a raw material. These include, for example, shed pupal skins or other chitin-rich components.

This raw material source is increasingly being researched. In commercial plant cultivation, however, it has so far played a much smaller role than crustacean or fungal chitosan.

Chitin, chitosan and chitosan oligosaccharides are not the same

These terms are often confused. However, they describe different materials.

Chitin

Chitin is the original natural substance. It is practically insoluble in water and relatively unreactive.

Chitin can nevertheless be interesting in Living Soil. It serves as a substrate for certain microorganisms. This can promote chitin-degrading microorganisms. This process tends to proceed slowly.

Chitosan

Chitosan is produced through the deacetylation of chitin. It has significantly more free amino groups and can become positively charged in an acidic solution.

This makes chitosan more biologically active and more suitable for targeted use as an elicitor.

Chitosan oligosaccharides

Chitosan oligosaccharides are often abbreviated as COS.

These are very short chitosan chains. They have a much lower molecular weight and are often more water-soluble than long-chain chitosan.

COS may behave differently from high-molecular-weight chitosan. They are more mobile and can interact more easily with biological systems. Dosages and effects therefore cannot simply be transferred between the forms.

Chitosan salts

Chitosan can also exist as a salt. One example is chitosan hydrochloride.

Such forms may have better water solubility. Nevertheless, they are not automatically the same material as ordinary chitosan powder, which is first dissolved in an organic acid.

Why is precise chitosan quality so important?

Chitosan is not a uniform substance with an identical effect every time.

Two products can both carry the name chitosan and still differ significantly.

The following are particularly important:

• molecular weight
• degree of deacetylation
• purity
• residual moisture
• ash content
• source material
• particle size
• chain-length distribution
• actual solubility
• acid used and pH of the solution

These properties influence how quickly chitosan dissolves, how viscous the solution becomes and how it affects plants or microorganisms. Scientific studies therefore regularly point out that molecular weight and degree of deacetylation must be taken into account when evaluating a chitosan product.

What does the degree of deacetylation mean?

The degree of deacetylation is often given as DD or DDA.

In simplified terms, it describes what proportion of the original acetyl groups in chitin were removed during production.

A higher degree of deacetylation generally means:

• more free amino groups
• a potentially higher charge density
• different solubility
• stronger interactions with surfaces
• different biological activity

However, a high degree of deacetylation alone does not automatically make a product better. Molecular weight and production also play an important role.

What does molecular weight mean?

Molecular weight provides information about the length of the chitosan chains.

In simplified terms, a distinction is made between:

• high-molecular-weight chitosan
• medium-molecular-weight chitosan
• low-molecular-weight chitosan
• chitosan oligosaccharides

The boundaries between these groups are not uniformly defined in the literature.

Low-molecular-weight forms usually dissolve more easily and may be more mobile. High-molecular-weight forms form longer polymer chains and often more viscous solutions. They may also adhere more strongly to treated surfaces.

Which form is best suited depends on the application.

One study with industrial hemp even compared three different molecular weights. In this trial, the lower concentration of 50 mg/L with low-molecular-weight chitosan led to the clearest changes in many of the plant substances examined. However, no general rule for every cannabis cultivar and every chitosan form can be derived from this.

CannaSelection chitosan

CannaSelection deliberately offers chitosan in powder form.

According to the specifications of our raw material supplier, the product has the following properties:

• raw material from crab shells
• purity of at least 90 percent
• degree of deacetylation of at least 85 percent
• molecular weight of approximately 300 to 800 kDa
• ash content of no more than 2 percent
• residual moisture of no more than 10 percent

This makes it a medium- to high-molecular-weight chitosan. It is not a directly water-soluble chitosan oligosaccharide.

The powder form offers several advantages. No unnecessary water is transported. The concentration can be adapted to the respective application. In addition, a fresh solution can be prepared precisely when it is needed.

However, this flexibility also requires correct processing. Chitosan powder should not simply be stirred into a finished nutrient solution.

Why does chitosan not dissolve in ordinary water?

Ordinary medium- or high-molecular-weight chitosan is only poorly soluble in water at neutral pH.

This is due to its amino groups.

In an acidic environment, these amino groups are protonated. They thereby acquire a positive charge. The polymer chains repel one another more strongly and can disperse better in water.

The relevant pKa value is approximately 6.5. The further the pH falls below this range, the more amino groups become protonated. Higher-molecular-weight chitosan therefore generally requires an acidic aqueous solution.

Dilute solutions of the following organic acids, for example, can be used for preparation:

• acetic acid
• citric acid
• lactic acid

The amount of acid required depends on the water and the chitosan concentration. Hard water with a high bicarbonate content binds significantly more acid than demineralized water.

A blanket recommendation such as “one milliliter of vinegar per liter” is therefore not reliable.

What is an elicitor?

Chitosan is primarily interesting as an elicitor.

An elicitor is a substance that is recognized by a plant as a biological signal. In response, the plant changes certain processes in its metabolism.

In simplified terms, it can be imagined as a fire drill.

The plant is not necessarily being attacked by a pathogen. However, it receives a signal that could correspond to a possible biological attack. It then increases its state of defense readiness.

Among other things, it can:

• activate defense enzymes
• produce protective proteins
• strengthen its cell walls
• change root exudates
• release signaling substances
• increase its antioxidant protection
• activate parts of its specialized metabolism

This process is called elicitation.

If the plant is prepared for later stress through prior treatment, this is also called priming.

Chitosan does not simply make the plant think it is being attacked by pests

The common explanation that “chitosan makes the plant believe it is being eaten by insects” is understandable. However, it is somewhat too simplistic.

Chitin-like structures occur in both fungi and arthropods. During their evolution, plants developed mechanisms that allow them to perceive certain of these structures.

Chitosan can therefore influence several signaling pathways. Exactly how a plant responds depends on the plant species, genetics, chitosan form, concentration and type of application.

It does not simply flip a single switch.

The plant adapts several processes simultaneously.

What has been directly demonstrated in cannabis?

For a long time, the effects of chitosan in cannabis cultivation were derived almost exclusively from research on other plant species.

There are now several studies directly involving Cannabis sativa.

This is important. Cannabis does not necessarily respond in the same way as tomato, maize, sage or Arabidopsis.

Activation of defense in the root zone

A study published in 2023 treated cannabis roots with chitin or chitosan.

Chitosan increased total chitinase activity in the roots. Several genes involved in plant defense were expressed three to five times more strongly.

The root exudates also changed.

Higher chitinase and peroxidase activities were measured there. In addition, the plant released more defense proteins. These included PR protein 1 and endochitinase 2.

Chitin did not trigger a comparable response in this experimental setup.

This directly demonstrates that cannabis perceives chitosan as a biologically active signal.

Changes in the phytochemical profile of the flowers

Another study examined foliar treatment of an industrial hemp cultivar during flowering.

The following were used:

• 50 mg/L chitosan
• 250 mg/L chitosan
• three different molecular weights

The treatment measurably changed the phytochemical profile of the flowers.

Depending on the treatment, the total content of phenolic compounds increased by 36 to 69 percent. Various tocopherols also increased significantly. At the lower concentration of 50 mg/L, the total content of the flavonoids examined increased by 12 to 27 percent.

The response depended on concentration and molecular weight. The lower dosage was more effective than the higher one for various measurements.

The study therefore directly demonstrates that chitosan can influence the specialized metabolism of cannabis flowers. However, it does not establish a general increase in THC or any other individual cannabinoid.

Chitosan and cannabis resin production

For CannaSelection, this is one of the most exciting areas of application.

Cannabis produces its resin primarily in glandular trichomes. These resin glands are particularly dense on female flowers and the leaves close to the flowers.

A complex secretion is produced and stored in the gland head.

It contains, among other things:

• cannabinoids
• monoterpenes
• sesquiterpenes
• flavonoids
• waxes
• lipids
• other specialized plant compounds

In grower terminology, this is often referred to as resin or oil.

Chemically, it is not a single oil. It is a complex mixture of various predominantly fat-soluble and volatile compounds.

What CannaSelection has observed in its own trials

CannaSelection has used chitosan in various cannabis cultures over several years.

We repeatedly observe:

• a higher visible quantity of resin
• heavier resin coverage on the flowers
• more oily secretion in the glands
• more intense aromatic expression
• more clearly recognizable cultivar-specific terpene profiles
• an overall higher sensory quality of the finished product

These observations were repeatedly made under our trial conditions. They are therefore relevant to our practical work.

Nevertheless, we do not describe them as a published scientific field study. Factors such as genetics, lighting, climate, maturity, nutrition and harvest timing also influence resin production.

Our statement is therefore not:

Chitosan guarantees a fixed percentage increase in resin quantity in every plant.

Our statement is:

In multi-year internal applications, CannaSelection repeatedly observes higher absolute resin production and better terpene expression in appropriately treated plants.

Why can chitosan influence resin production?

Resin is not a useless by-product for the cannabis plant.

The substances it contains serve various protective functions. Among other things, they can support the plant in defending itself against herbivores, microorganisms and environmental influences.

Chitosan activates precisely those areas of the plant associated with defense and specialized metabolism.

One possible sequence is:

1. The plant perceives chitosan as a biological signal.
2. Defense and stress signaling pathways are activated.
3. Gene activity and enzyme activity change.
4. The plant invests more in protective substances and specialized metabolites.
5. This can also alter the activity of resin-producing tissues.

Existing cannabis research confirms the first four points in various areas. It shows activated defense genes, more defense enzymes and a changed composition of flower compounds.

However, the literature we evaluated has not yet clearly examined whether the higher visible resin quantity results from more glandular trichomes, larger gland heads or more secretion per gland.

More visible resin can generally have various causes:

• a higher density of glandular trichomes
• larger trichome heads
• more heavily filled secretion chambers
• higher production by individual glands
• a changed composition of the secretion
• a combination of several factors

This area should be specifically investigated microscopically and gravimetrically in future cannabis studies.

More resin does not automatically mean more THC

This distinction is central.

The percentage THC content of a flower sample and the absolute amount of resin produced are not the same thing.

A plant can produce more resin without the THC concentration within that resin increasing.

In simplified terms:

• more resin means more secretion produced
• more THC percentage means a higher THC concentration in the sample examined
• both can change independently of one another

CannaSelection therefore makes no blanket claim regarding an increase in THC.

Our observations relate to:

• absolute resin production
• the visible and tangible quantity of resin
• aromatic intensity
• sensory quality
• the expression of the genetically present terpene profile

Genetics remain the foundation.

Chitosan cannot create terpenes in a cultivar if it lacks the genetic prerequisites to produce them.

However, it can influence how strongly existing metabolic pathways are used under the respective growing conditions.

Chitosan and terpenes

Terpenes shape a large part of a cannabis cultivar’s aroma.

They are produced through various metabolic pathways and are sensitive to:

• genetics
• light intensity
• temperature
• water availability
• nutrient supply
• developmental stage
• harvest timing
• drying
• storage
• biological signaling substances

Chitosan should therefore not be understood as a simple “terpene booster.”

The more accurate description is:

Chitosan is an elicitor that can influence specialized plant metabolism.

In various aromatic plants, changes in the quantity and composition of essential oils have been observed following chitosan treatments. Results differ depending on plant species, dose and environmental conditions. In a study of Salvia species under drought stress, chitosan nanoparticles influenced both physiological parameters and essential oil production. These results cannot be transferred directly to cannabis or ordinary chitosan powder. However, they show that chitosan-based elicitation can also influence terpene metabolic pathways.

Our own observation in cannabis is less a completely new aroma. Rather, the existing terpene profile often appears:

• more intense
• clearer
• deeper
• more cultivar-specific
• more complete from a sensory perspective

This statement is also based on internal CannaSelection applications and sensory comparisons. No universally applicable guarantee can be derived from it.

A controlled stimulus is not the same as harmful stress

In the grow sector, people often say:

“Stress produces more resin.”

This statement is too simplistic.

Severe stress can impair photosynthesis, water uptake, root growth and flower development. A plant under constant excessive strain does not automatically produce a better end product.

Chitosan is therefore not used to place the plant under maximum stress.

The goal is a controlled stimulus.

The plant should be able to respond without its basic growth processes being significantly restricted.

This is precisely why dosage is so important.

With elicitors, the following does not apply:

More active substance automatically produces a stronger effect.

Often, the best response occurs within a relatively low concentration range. An excessively high concentration can place unnecessary stress on the plant.

Chitosan and the root system

Chitosan is often marketed as a root stimulator.

This may be true. However, it is not a blanket effect.

In various crops, positive effects on root development, nutrient uptake and plant vitality have been observed following low or appropriately formulated applications.

At the same time, direct cannabis studies show that high concentrations in the root zone can significantly inhibit root growth.

One cannabis study used 0.1 percent, 0.2 percent and 0.5 percent colloidal chitosan. This corresponds to 1, 2 and 5 g/L.

The defense response was strongly activated. Under these experimental conditions, however, root growth was severely inhibited. Above-ground development was much less affected.

That is not a contradiction.

The plant had to reallocate resources from growth to defense.

The most important practical conclusion is therefore:

Chitosan can biologically activate the root zone. However, excessive amounts can slow the roots down.

What are root exudates?

Roots do not only absorb water and nutrients.

They also constantly release substances into their surroundings.

These substances are called root exudates. They include, among other things:

• sugars
• amino acids
• organic acids
• enzymes
• proteins
• signaling substances
• phenolic compounds

Through these secretions, the plant influences its immediate surroundings.

It can attract microorganisms, mobilize nutrients and alter its defense against pathogens.

In cannabis, chitosan increased the release of various defense enzymes and protective proteins through the roots. In tomatoes, chitosan treatment also caused changes in hormones, lipid signals, phenolic compounds and defense substances in root exudates.

This is particularly interesting for Living Soil.

The plant does not only defend its own tissues. It actively changes the conditions around its roots.

Direct and indirect effects against fungi

Chitosan can act against plant-pathogenic fungi in two ways.

Direct effect

In an acidic solution, chitosan carries positive charges.

These can interact with negatively charged structures on the cell surfaces of microorganisms. Depending on the chitosan form, pH, concentration and fungal species, this can impair membrane functions, spore germination or hyphal growth.

The effect is not identical for every fungus. In a comparative study, plant-pathogenic and mycoparasitic fungi were in some cases more sensitive than beneficial nematode- or insect-pathogenic fungi.

Indirect effect

Chitosan can place the plant itself in a heightened state of defense readiness.

The plant then produces, among other things:

• chitinases
• peroxidases
• PR proteins
• other defense substances

Chitinases can break down chitin-rich structures. Since many fungal cell walls contain chitin, these enzymes are an important part of plant defense.

The indirect effect has been directly demonstrated in cannabis.

Does chitosan help against root diseases?

Chitosan has interesting potential against soil-borne pathogens.

However, it is not a reliable curative agent for every root disease.

In a cannabis study, roots were treated with 0.2 percent colloidal chitosan before infection with Athelia rolfsii. The fungus causes the disease known as Southern blight.

The chitosan treatment activated root defense. Among other things, peroxidase activity increased. More defense-related proteins were also found.

Under the experimental conditions, however, the infection was not completely prevented. Both treated and untreated plants developed disease symptoms. At the same time, root growth was significantly restricted by the high chitosan concentration.

The correct classification is therefore:

Chitosan can prepare cannabis for an attack and activate root-zone defense. It does not replace root-cause analysis or targeted treatment of an already advanced root disease.

Chitosan against Fusarium, Alternaria and other soil fungi

A 2025 field study examined the effect of chitosan on natural soil microbiomes.

Chitosan primarily altered the composition of the fungal community.

The chitosan solution studied reduced the occurrence of Fusarium falciforme by approximately 50 percent. A chitosan coacervate formulation reduced Alternaria atra by approximately 20 percent.

In the same study, no comparably strong change was observed in the overall bacterial community.

These results did not come from cannabis crops. However, they show that chitosan does not simply sterilize soil completely.

The effect may be selective.

Can chitosan prevent Botrytis or powdery mildew?

Chitosan has antifungal and plant-strengthening properties.

However, this must not be interpreted to mean that chitosan treatment reliably prevents bud rot or powdery mildew.

For these diseases, the most important measures remain:

• stable climate management
• sufficient air movement
• appropriate humidity
• clean plant stock
• removal of infected plant parts
• appropriate plant spacing
• no persistently wet flowers
• early detection

Chitosan can be part of a preventive system. It does not replace that system.

Especially during advanced flowering, foliar treatment itself can become problematic. Every spray solution adds moisture to the flowers and leaves substances on the surface.

CannaSelection therefore does not recommend unnecessary foliar treatment on dense, well-developed flowers.

Does chitosan have insecticidal effects?

Direct and indirect effects of chitosan have been described for various insects.

Possible effects include:

• reduced feeding activity
• growth inhibition
• impaired development
• increased mortality
• altered plant defense
• use as a carrier substance for other active ingredients

The effect depends heavily on the insect species and the chitosan form.

One study tested four different molecular weights against oleander aphids and cotton leafworms.

For two chitosan variants, mortality rates of 48 and 49 percent, respectively, were observed in aphids after 24 hours. A concentration of 1,000 mg/L was used.

In the caterpillars, feeding inhibition and delayed growth were also examined. Here too, the effect depended on molecular weight.

These results demonstrate insecticidal potential.

However, they do not mean that every chitosan at every dosage reliably works against every cannabis pest.

Direct and plant-mediated effects on pests

Two levels must also be distinguished for insects.

Direct effect

The pest itself comes into contact with chitosan or consumes it through food.

Depending on the species and formulation, feeding, development or survival may be affected.

Indirect effect through the plant

Chitosan activates the plant’s own defense.

This can change the composition of the plant tissue. The plant may become less attractive or more difficult for a feeding pest to utilize.

The second effect is less comparable to a conventional contact insecticide.

Chitosan does not kill the pest immediately. It changes the plant’s readiness to respond.

Chitosan against fungus gnats

Fungus gnats are particularly relevant to cannabis cultivation.

Their larvae live in moist substrate. They mainly feed on fungal material and organic components, and in heavier infestations also on young roots and root hairs.

Chitosan is interesting for this area for several reasons:

• It can alter the fungal community in the substrate.
• It can activate root defense.
• It changes root exudates.
• It can promote certain microorganisms and inhibit others.
• Feeding-inhibitory and development-inhibitory effects are known for other insect species.

Nevertheless, there is currently no robust direct cannabis study demonstrating reliable control of fungus gnat larvae using ordinary chitosan powder.

Therefore, it should not be claimed:

Chitosan reliably kills fungus gnats.

The correct statement is:

Chitosan is an interesting component of a biological root-zone and prevention system. For an acute fungus gnat infestation, targeted measures such as BTI, SF nematodes, adapted irrigation and yellow sticky traps should still be used.

Chitosan against thrips, aphids and spider mites

Aphids

Direct studies exist for individual aphid species. The results indicate a possible effect. However, they are dose- and species-specific.

Thrips

The data is significantly weaker for ordinary chitosan as a standalone measure against thrips.

Activated plant defense can fundamentally help. However, in an existing infestation, chitosan does not replace beneficial organisms or suitable contact measures.

Spider mites

Spider mites are not insects but arachnids.

Chitosan should not be understood as a reliable contact agent against spider mites. For reliable control, predatory mites and suitable direct measures remain much better researched.

Root aphids

There is also a lack of robust direct cannabis data for root aphids.

Improved root defense may provide support. However, with an established infestation, an elicitor treatment alone is very unlikely to be sufficient.

Chitosan and nematodes

Chitosan is also being studied in connection with plant-parasitic nematodes.

The effect may have several causes:

• direct influence on nematodes
• activation of plant defense
• alteration of the rhizosphere
• promotion of nematode-feeding or nematode-parasitizing microorganisms

In the field study already mentioned, a naturally occurring fungus of the genus Purpureocillium increased approximately fiftyfold after a specific chitosan formulation.

Purpureocillium includes species known as antagonists of nematodes and other invertebrates. This does not mean that every chitosan application automatically eliminates nematodes. However, it shows how strong the indirect effect through the soil microbiome can be.

Chitosan in Living Soil

At first glance, chitosan appears contradictory to Living Soil.

Why add a substance with antimicrobial effects to a living soil?

The answer is:

Antimicrobial does not automatically mean sterilizing.

Chitosan does not affect every microorganism in the same way. The response depends on:

• microorganism species
• chitosan form
• molecular weight
• concentration
• pH
• contact time
• substrate composition
• organic matter
• existing chitosanases and chitinases

Some microorganisms can break down chitosan or chitin and use them as a nutrient source. Others are sensitive.

Trials with various fungi showed significant differences. Plant-pathogenic and mycoparasitic fungi were in some cases more sensitive than certain beneficial insect- or nematode-pathogenic fungi.

The field study also does not show complete sterilization. It primarily altered the fungal community. Certain pathogenic species declined. A potentially beneficial antagonist increased significantly. The composition of the bacterial community changed considerably less in the same experimental setup.

Is chitosan harmful to mycorrhiza?

This question cannot be answered with a blanket yes or no.

High chitosan concentrations can fundamentally also impair beneficial fungi.

At the same time, studies with certain chitosan oligosaccharides show that short chitin signals can even promote the formation of arbuscular mycorrhiza in certain plants. This was observed, for example, in Medicago truncatula.

This does not mean that high-molecular-weight chitosan automatically promotes every type of mycorrhiza.

Chitosan oligosaccharides and CannaSelection chitosan powder are not the same form.

For practical use, this means:

• use low and targeted dosages
• do not stir mycorrhiza directly into a concentrated chitosan solution
• apply concentrated products at separate times
• first test new combinations on a small number of plants
• do not carry out unnecessarily frequent root treatments

Chitosan and MicroBio+

MicroBio+ contains living microorganisms.

Depending on concentration and pH, chitosan can have antimicrobial effects. A concentrated and acidic chitosan stock solution should therefore not be mixed directly with MicroBio+ and stored.

The more sensible approach is to apply them at separate times.

Based on CannaSelection practice, we recommend:

• do not prepare chitosan together with MicroBio+ in a concentrated stock solution
• dilute both products separately
• allow a gap of preferably 24 to 48 hours between applications
• only apply MicroBio+ once the root zone is no longer in contact with a concentrated acidic chitosan solution
• start with a small test group when trying new combinations

This does not mean that the two approaches fundamentally contradict one another.

Chitosan provides a targeted stimulus and influences the rhizosphere. MicroBio+ subsequently supports the development and stabilization of the microbial system.

The sequence and correct dilution are decisive.

Chitosan and abiotic stress

Not every stress affecting a plant is caused by pests or pathogens.

The following factors also cause stress:

• drought
• salt stress
• high temperatures
• strong changes in light
• transplanting
• root damage
• heavy defoliation
• fluctuations in water supply

Chitosan can activate various signaling and antioxidant systems. In the cannabis root studies, changes in abscisic acid balance were observed, among other things. Abscisic acid plays an important role in water balance and stress responses.

Other plant species have been studied to determine whether chitosan can mitigate the effects of drought or salt stress. In some cases, water balance, antioxidant protection and plant development improved.

These results are interesting. However, they must not be understood as a blanket guarantee for cannabis.

Chitosan can help a plant activate its own protective mechanisms more quickly. It does not replace correct watering or a suitable climate.

Foliar or root treatment?

Both application methods can be useful. However, they do not pursue exactly the same objective.

Foliar treatment

With foliar treatment, chitosan comes into direct contact with the plant surface.

Possible benefits:

• direct elicitation of leaf tissue
• even distribution when finely sprayed
• potential film formation on the surface
• good control over the applied concentration
• rapid response of the treated tissues

The industrial hemp study using 50 and 250 mg/L involved foliar treatments during flower development.

For cannabis cultivation, foliar treatment should nevertheless mainly take place during the vegetative phase or very early flowering.

Advanced flowers should not be sprayed unnecessarily.

Root treatment

With root treatment, chitosan enters the rhizosphere.

Possible effects:

• activation of root defense
• alteration of root exudates
• influence on the fungal community
• support of a resilient root environment

The biggest mistake here is excessive dosage.

Cannabis studies clearly show that gram quantities per liter in the hydroponic root zone can severely restrict root growth.

Seeds and cuttings

Chitosan is also being studied in various plants as a seed treatment or during early rooting.

Particular caution applies to cannabis cuttings.

Young, not-yet-rooted cuttings have little reserve. An excessively strong elicitor stimulus can hinder rather than help at this stage.

Treatment should therefore be dosed very low and first tested on only a few cuttings.

When is chitosan particularly interesting for cannabis?

From our perspective, the following timings are especially suitable:

Vegetative phase

Chitosan can be used here to prepare the plant early for biological stress.

The leaves are easily accessible, and foliar treatment does not yet cause residues on mature flowers.

After transplanting

A cautious application may be useful once the plant has resumed active growth after transplanting.

Immediately after severe root injury, an unnecessarily strong stimulus should not be applied.

Before known stress phases

These may include major climate changes or the transition to a more intense light phase.

The plant should be healthy and adequately supplied.

Early flowering

This is when strong formation of flower and resin structures begins.

Controlled elicitation can be particularly interesting here. Foliar treatments should be stopped before the flowers become dense and moisture can dry less effectively.

During mid-flowering

Here we prefer applications that do not unnecessarily wet finished flowers.

Whether a root application is appropriate depends on the system, concentration and condition of the plant.

Late flowering

During late flowering, one should not attempt to force more resin at short notice through a strong final treatment.

By this point, the plant has already completed much of its developmental program.

Spraying too late also increases the risk of residues and moisture in the flowers.

How is chitosan powder dissolved correctly?

CannaSelection chitosan is not intended to be stirred directly into neutral water.

A sensible basic procedure is:

1. Use soft or demineralized water

Hard tap water can make preparation more difficult. Bicarbonate neutralizes some of the acid.

Demineralized water makes the preparation easier to control.

2. Acidify part of the water

Part of the required amount of water is adjusted to a clearly acidic pH using a diluted organic acid.

For the initial solution, a range of approximately pH 3.5 to 4 is often favorable.

Depending on the application, suitable options include:

• acetic acid
• citric acid
• lactic acid

Always add the acid carefully and measure the pH.

3. Sprinkle in the chitosan slowly

The powder is slowly added to the acidic water phase while stirring vigorously.

If the entire quantity is added at once, lumps may form. The material dissolves on the outside while dry powder remains trapped inside.

4. Allow time for swelling

Medium- and high-molecular-weight chitosan does not dissolve immediately.

The solution should be stirred sufficiently and then given time to swell. Depending on concentration and temperature, this process can take significantly longer than a few minutes.

5. Top up with the remaining water

Only once the chitosan is evenly distributed should the solution be brought to the desired total volume.

6. Check the final pH

The finished application solution should not be uncontrolled and strongly acidic.

At the same time, the pH must not be raised so far that the chitosan precipitates again.

High-molecular-weight chitosan increasingly loses its solubility above the mildly acidic range. A final pH below approximately 6 is therefore usually necessary. Plant tolerance and the respective growing system must nevertheless be taken into account.

7. Use fresh

Self-prepared chitosan solutions should not be stored unnecessarily long.

The pH, viscosity and microbiological stability may change.

Why we do not specify a fixed amount of acid

The amount of acid required depends on several factors:

• water hardness
• bicarbonate content
• acid used
• acid concentration
• amount of chitosan
• degree of deacetylation
• molecular weight
• desired final pH

A pH meter should therefore be used.

A formula without measurement may be too acidic with soft water and completely insufficient with hard water.

Study concentrations are not general dosage instructions

The industrial hemp study used 50 and 250 mg/L as foliar treatments.

This corresponds to:

• 0.05 g/L
• 0.25 g/L

At 50 mg/L, stronger positive changes were observed in several groups of substances examined than at 250 mg/L.

The cannabis root studies used significantly higher concentrations of 1 to 5 g/L or 2 g/L, respectively.

Although these quantities triggered clear defense responses, they also inhibited root growth.

These differences show why study values must not simply be adopted.

The decisive factors are:

• foliar or root application
• chitosan form
• molecular weight
• solution
• plant age
• frequency
• cultivar
• growing system

For CannaSelection chitosan, the current application instructions on the product label and product page apply.

When trying a new application, always begin with a small group of plants.

How often should chitosan be used?

Chitosan is not a base fertilizer that is necessarily required with every watering.

Elicitation relies on a targeted stimulus.

Continuous or overly frequent application can cause the plant to invest unnecessarily much energy in defense instead of growth.

The appropriate frequency depends on the application and concentration.

As a general rule:

• do not automatically use it with every watering
• observe the plants’ responses
• allow sufficient time between applications
• do not increase the dose simply because there is no immediate response
• do not expose plants to several strong elicitors at the same time

Resin production and metabolic changes are not an immediate contact reaction. The plant needs time to respond to the signal.

What should not be mixed with a chitosan stock solution?

Concentrated chitosan solutions can react sensitively to other components.

The following can be particularly problematic:

• strongly alkaline products
• silicates
• carbonates
• concentrated calcium solutions
• highly concentrated fertilizers
• hydrogen peroxide
• other strong oxidizing agents
• concentrated microbial products
• untested plant protection products

An unfavorable combination can cause chitosan to flocculate or lose its solubility.

Interactions with other active substances are also possible.

Therefore:

• prepare concentrates separately
• first dilute in sufficient water
• test miscibility in a small container
• do not use a solution that flocculates or gels
• check the pH before application

Common mistakes with chitosan

Adding the powder directly to tap water

The chitosan floats, clumps or settles. This does not produce an even application.

Using too high a dosage

More chitosan does not automatically mean more resin or stronger roots. High root-zone concentrations can significantly inhibit root growth.

Ignoring the chitosan form

A study result with low-molecular-weight chitosan or COS cannot be directly transferred to a high-molecular-weight powder.

Ignoring the pH

Without sufficiently acidic conditions, ordinary chitosan dissolves poorly. Conversely, an excessively acidic finished application solution can stress the plant.

Spraying directly onto mature flowers

This can result in residues, additional moisture and an increased risk of flower problems.

Viewing chitosan as an acute treatment for every pest

Chitosan can influence plant defense and certain pests. However, it is not a universal substitute for targeted pest control.

Equating chitosan with chitin

Both substances can be useful. However, they do not act identically and are processed differently.

Promising an increase in THC

The research available to date does not support such a blanket claim.

Completely ignoring soil life

In a biological system, chitosan should be used in a controlled manner. Concentrated solutions should not be applied directly to living microbial preparations.

What chitosan can do and what has not yet been sufficiently established

Is chitosan a fertilizer?

No.

Chitosan does contain organically bound carbon and nitrogen. However, the quantities typically used do not make it a conventional nitrogen fertilizer.

Its primary effects lie in:

• elicitation
• plant strengthening
• altering the defense response
• influencing root exudates
• interacting with microorganisms
• potentially influencing specialized metabolism

It should therefore not be used to compensate for inadequate basic nutrition.

Can chitosan compensate for poor genetics?

No.

Genetics determine, among other things:

• which cannabinoids can be produced
• which terpenes are fundamentally present
• how many resin glands are formed
• the yield potential
• how the plant responds to stress signals

Chitosan can influence existing processes.

However, it cannot create traits that are not genetically present.

A weakly aromatic genetic background will not suddenly become a completely different cultivar.

Does chitosan work the same way in every cannabis cultivar?

Very probably not.

The industrial hemp study used a single cultivar. Even there, the results differed depending on molecular weight and concentration.

Cannabis cultivars differ considerably in:

• growth type
• resin gland density
• terpene biosynthesis
• ripening time
• stress response
• hormonal balance
• root development
• susceptibility to pathogens

Different responses should therefore be expected.

What is highly visible in one cultivar may be significantly weaker in another.

Is chitosan suitable for Hydro, Coco and soil?

In principle, chitosan can be used in different systems.

However, the application must be adapted.

Hydroponics

In hydroponics, chitosan reaches the roots directly. This can make the effect strong.

At the same time, there is an increased risk of:

• root inhibition from overdosing
• flocculation
• deposits
• filter or line problems
• interactions with nutrient salts
• unstable pH values

A concentrated stock solution should therefore never be added to a tank without testing.

Coco

Coco has less biological buffering than an active Living Soil.

A root application can act relatively directly. Here too, begin with a low dosage and observe the plant response.

Organic soil

Organic soil also involves interactions with humic substances, microorganisms and organic matter.

The system can buffer certain effects. At the same time, chitosan is biologically processed.

Living Soil and No-Till

Here, it is not only the plant’s response that matters.

Long-term changes in fungal and bacterial communities must also be taken into account.

Targeted applications are more sensible than continuously using a high dosage with every watering.

Safety when handling chitosan powder

Fine powder should generally not be inhaled.

The following are advisable during processing:

• gloves
• clean equipment
• safety goggles when handling acids
• a suitable dust mask when significant dust is generated
• good ventilation
• slow stirring in rather than pouring

CannaSelection chitosan is derived from crab shells.

People with a pronounced crustacean allergy should therefore take particular care when handling the dry powder. Even at high purity, minor residual components cannot be completely ruled out depending on the production process without product-specific analysis.

Always use acids diluted and in a controlled manner.

Legal classification

In 2022, chitosan was approved in the European Union as a basic substance within the meaning of plant protection law. The approval applies under the conditions set out in the European assessment and approval documents.

This does not automatically mean that every chitosan product may be advertised with every conceivable fungicidal or insecticidal claim.

Relevant factors include:

• precise substance identity
• purity
• intended use
• product presentation
• application recommendation
• specific advertising claims
• national implementation and monitoring

A raw material, a plant-strengthening product and an approved plant protection product are not automatically the same thing legally.

This article describes the biological properties and the current state of research. Specific use is governed by the current product information and the applicable legal requirements.

Chitosan powder at CannaSelection

CannaSelection now offers chitosan as a pure powder for the individual preparation of application solutions.

The powder form is intended for growers who want to control their own applications and value transparent raw material data.

It allows:

• flexible concentration
• freshly prepared solutions
• foliar or root applications depending on the concept
• lower transport weight
• no unnecessary pre-diluted liquid
• in-house trials with documented dosage

At the same time, a pure powder requires more care than a ready-formulated liquid product.

The pH must be controlled. The chitosan must be completely dissolved. The concentration must be suitable for the application method.

Chitosan is not a product for the “more is better” principle.

Used correctly, it is a highly interesting tool for growers who do not merely want to provide nutrients but want to work deliberately with the biological responses of their plants.

Our conclusion

Chitosan does not belong in the category of ordinary grow boosters.

It does not work by simply supplying the plant with more nutrients.

It sends a signal.

Cannabis responds with measurable changes:

• Defense genes are activated.
• Chitinase and peroxidase activities increase.
• The composition of root exudates changes.
• Protective proteins are released.
• The phytochemical profile of the flowers can be influenced.

These effects have been studied directly in cannabis or industrial hemp.

In addition, CannaSelection observes higher absolute resin quantity and better terpene expression in multi-year internal applications.

We do not claim that chitosan generally increases THC content.

We see its benefit elsewhere.

Chitosan can provide a healthy and well-supplied cannabis plant with a controlled biological stimulus. This may enable it to activate its defense and specialized metabolism more strongly.

This may manifest as a more robust plant response, a more active root zone, more resin and more intense expression of the existing terpene profile.

The prerequisite is proper application.

The right chitosan form, a low and appropriate dosage, the correct pH and a sensible timing determine whether an interesting raw material becomes an effective tool.

Frequently asked questions about chitosan in cannabis

Does chitosan increase THC content?

CannaSelection does not make this claim.

Existing research shows that chitosan can influence the specialized metabolism of cannabis. A blanket and reliable increase in THC cannot be derived from this.

Does chitosan increase resin quantity?

In multi-year internal trials, CannaSelection has repeatedly observed a higher absolute resin quantity.

A published cannabis study on the exact absolute resin mass per flower is not yet available in the literature we evaluated.

Does chitosan improve terpenes?

Our internal applications often show more intense and clearer terpene expression.

The strength of this effect depends on genetics, the growing environment, dosage and timing.

Is chitosan the same as chitin?

No.

Chitosan is produced from chitin. Deacetylation changes solubility, charge and biological activity.

Can chitosan simply be stirred into water?

Ordinary medium- to high-molecular-weight chitosan dissolves poorly in neutral water.

It must first be dissolved in a sufficiently acidic water phase.

Is chitosan suitable for Living Soil?

Yes, when used in a controlled manner.

However, it should not be used continuously at high dosages. Its effect on microorganisms is selective and depends on many factors.

Can chitosan be used together with MicroBio+?

Yes, but not as a concentrated joint stock solution.

CannaSelection recommends separate applications with an interval between them.

Does chitosan kill fungus gnats?

A reliable direct effect against fungus gnats in cannabis substrates has not yet been sufficiently established.

Chitosan can influence the root zone and fungal community. Nevertheless, targeted measures should be used in the event of an acute infestation.

Can chitosan cure root rot?

Chitosan can activate root defense and influence certain pathogens.

An advanced root disease is not automatically cured by this. The cause, irrigation, temperature, oxygen supply and pathogen must be taken into account.

Should chitosan be used with every watering?

No.

Chitosan is an elicitor, not a base fertilizer. Targeted applications with sufficient intervals are more sensible than continuous high stress.

Can chitosan be sprayed during late flowering?

CannaSelection does not recommend unnecessary foliar treatment on dense and mature flowers.

Additional moisture and residues on the finished product should be avoided.

Scientific sources and further reading

1. Beleggia R. et al. 2023: Impact of Chitosan-Based Foliar Application on the Phytochemical Content and the Antioxidant Activity in Hemp Inflorescences. Plants, 12, 3692. DOI: 10.3390/plants12213692. The study examined 50 and 250 mg/L chitosan with different molecular weights on industrial hemp flowers.
2. Suwanchaikasem P. et al. 2023: Effects of chitin and chitosan on root growth, biochemical defense response and exudate proteome of Cannabis sativa. Plant-Environment Interactions, 4, 115 to 133. DOI: 10.1002/pei3.10106. Direct evidence of altered defense genes, enzymes and root exudates in cannabis.
3. Suwanchaikasem P. et al. 2023: Hormonal and proteomic analyses of southern blight disease caused by Athelia rolfsii and root chitosan priming on Cannabis sativa. Plant Direct, 7, e528. DOI: 10.1002/pld3.528. Study of root defense and the limitations of high-dose chitosan treatment.
4. Pellis A. et al. 2022: Chitosan: Sources, Processing and Modification Techniques. Overview of raw material sources, chitin extraction, deacetylation and chitosan modification.
5. Aranaz I. et al. 2021: Chitosan: An Overview of Its Properties and Applications. Description of the relationships between molecular weight, deacetylation, charge, solubility and biological activity.
6. Suarez-Fernandez M. et al. 2020: Chitosan Induces Plant Hormones and Defenses in Tomato Root Exudates. Study of changes in hormones, lipid signals and defense substances in root exudates.
7. Badawy M. E. I. and El-Aswad A. F. 2012: Insecticidal activity of chitosans of different molecular weights against cotton leafworm and oleander aphid. Plant Protection Science, 48, 131 to 141. DOI: 10.17221/67/2010-PPS.
8. Palma-Guerrero J. et al. 2008: Effect of chitosan on hyphal growth and spore germination of plant pathogenic and biocontrol fungi. Journal of Applied Microbiology, 104, 541 to 553. DOI: 10.1111/j.1365-2672.2007.03567.x.
9. Lopez-Nuñez R. et al. 2025: Chitosan reduces naturally occurring plant pathogenic fungi and increases nematophagous fungus Purpureocillium in soil under field conditions. Frontiers in Agronomy. DOI: 10.3389/fagro.2024.1502402.
10. Volpe V. et al. 2023: Long-lasting impact of chitooligosaccharide application on fungal accommodation promotes arbuscular mycorrhiza in Medicago truncatula. New Phytologist. DOI: 10.1111/nph.18697.
11. European Commission 2022: Commission Implementing Regulation (EU) 2022/456 approving chitosan as a basic substance pursuant to Regulation (EC) No 1107/2009.