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 a standard root stimulator or a simple contact agent against pests.

Chitosan primarily acts as a biological signal.

The plant recognizes certain structures in chitosan and responds to them. It activates defense mechanisms. It changes the composition of its root exudates. It forms 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 amount of resin on treated flowers. The resin appeared more pronounced, and the plants’ aromatic expression was more intense and clearer.

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

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

Our results are internal practical observations. They have been 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 interconnected 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
• exoskeletons of insects
• cell walls of various fungi

Chitin is a stable structural substance. Through chemical or enzymatic processing, some of its acetyl groups are removed. This process is called deacetylation.

Chitosan is produced from chitin as a result.

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, besides chitin, they also contain calcium compounds, proteins, pigments and other components.

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

In simplified terms, conventional production proceeds as follows:

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

The finished chitosan is therefore a processed biopolymer. It should 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 disposing of them, 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 naturally 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 interesting for applications that intentionally avoid animal-derived starting materials.

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

Chitosan from insects

Insects also contain chitin.

By-products from insect farming can therefore in principle also serve as raw materials. 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 currently plays 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. The process tends to occur 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 better suited for targeted use as an elicitor.

Chitosan oligosaccharides

Chitosan oligosaccharides are often abbreviated as COS.

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

COS can 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 occur 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 must first be 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 bear the name chitosan and still differ considerably.

The following are particularly important:

• molecular weight
• degree of deacetylation
• purity
• residual moisture
• ash content
• starting 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 publications 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 the proportion of the original acetyl groups in chitin that 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 indicates 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 generally 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 most suitable 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 produced the clearest changes in many of the plant compounds examined. However, this cannot be used to derive a general rule for every cannabis cultivar and every form of chitosan.

CannaSelection chitosan

CannaSelection deliberately offers chitosan in powder form.

According to the specifications provided by 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 is therefore 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 adjusted to the specific application. In addition, a fresh solution can be prepared exactly when 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 normal water?

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

This is due to its amino groups.

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

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

• 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 instruction 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 a plant recognizes as a biological signal. The plant then 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 potential 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 its root exudates
• release signaling compounds
• increase its antioxidant protection
• activate parts of its specialized metabolism

This process is called elicitation.

If the plant is prepared for subsequent stress through prior treatment, this is also referred to as priming.

Chitosan does not simply trick the plant into thinking it is being attacked by pests

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

Chitin-like structures occur in both fungi and arthropods. Over the course of their evolution, plants have 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, form of chitosan, concentration and application method.

A single switch is therefore not simply flipped.

The plant adjusts several processes simultaneously.

What has been demonstrated directly 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, corn, sage or Arabidopsis.

Activation of defense in the root zone

In a study published in 2023, cannabis roots were treated 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 recognizes 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.

The total content of phenolic compounds increased by 36 to 69 percent depending on the treatment. 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 shows 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 mainly 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 observed in its own trials

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

We repeatedly observe:

• a higher visible amount 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 final product

These observations have been repeated 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 formation.

Our statement is therefore not:

Chitosan guarantees a fixed percentage increase in resin production for 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 formation?

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 that are associated with defense and specialized metabolism.

A possible sequence is:

1. The plant recognizes 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 may 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 amount results from more trichomes, larger trichome heads or more secretion per gland.

More visible resin can in principle have various causes:

• a higher density of glandular trichomes
• larger trichome heads
• more fully 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 percent means a higher THC concentration in the sample examined
• both can change independently of each other

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

Our observations concern:

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

Genetics remain the foundation.

Chitosan cannot produce terpenes that a cultivar lacks the genetic prerequisites to form.

However, it may influence how strongly existing metabolic pathways are used under the respective cultivation 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 compounds

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 amount and composition of essential oils have been observed after 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 about 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 generally applicable guarantee can be derived from it.

A controlled stimulus is not the same as harmful stress

In the grow sector, it is often said:

"Stress produces more resin."

This statement is too simplistic.

Severe stress can impair photosynthesis, water uptake, root growth and flower development. A plant that is permanently overburdened does not automatically produce a better final product.

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

The goal is a controlled stimulus.

The plant should be able to respond without its fundamental 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.

The best response often 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 universal effect.

In various crops, positive effects on root development, nutrient uptake and plant vitality have been observed after 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.

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

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

This is not a contradiction.

The plant had to reallocate resources from growth to defense.

The most important practical insight is therefore:

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

What are root exudates?

Roots take up more than just water and nutrients.

They also continuously release substances into their surroundings.

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

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

Through these secretions, the plant influences its immediate environment.

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 produced changes in hormones, lipid signals, phenolic compounds and defense substances in the root exudates.

This is particularly interesting for Living Soil.

The plant does not only defend its own tissue. 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 acidic solution, chitosan carries positive charges.

These can interact with negatively charged structures on the cell surfaces of microorganisms. Depending on the form of chitosan, pH, concentration and fungal species, this may 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 entomopathogenic or nematophagous fungi.

Indirect effect

Chitosan can place the plant itself in a state of increased 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 guaranteed treatment for every root disease.

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

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

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

The correct interpretation is therefore:

Chitosan can prepare cannabis for an attack and activate defenses in the root zone. It does not replace 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 in the overall bacterial community was observed.

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

The effect can be selective.

Can chitosan prevent Botrytis or powdery mildew?

Chitosan has antifungal and plant-strengthening properties.

However, this does not mean that chitosan treatment will reliably prevent bud rot or powdery mildew.

For these diseases, the most important measures remain:

• stable climate control
• sufficient air movement
• appropriate humidity
• clean plant stock
• removal of infected plant parts
• suitable plant spacing
• avoiding persistently wet flowers
• early detection

Chitosan can be part of a preventive system. However, 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
• disrupted 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 form of chitosan.

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.

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

These results demonstrate insecticidal potential.

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

Direct and plant-mediated effects on pests

In insects, too, two levels must be distinguished.

Direct effect

The pest itself comes into contact with chitosan or ingests 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 alter 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 immediately kill the pest. 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 feed primarily on fungal material, organic components and, in cases of heavier infestation, also on young roots and root hairs.

Chitosan is interesting in this area for several reasons:

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

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

It should therefore not be claimed that:

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 show a possible effect. However, they are dose- and species-specific.

Thrips

The evidence for ordinary chitosan as a stand-alone measure against thrips is considerably weaker.

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

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, once an infestation is established, 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 was applied.

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

Chitosan in Living Soil

At first glance, chitosan appears contradictory to Living Soil.

Why add an antimicrobial substance 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
• form of chitosan
• molecular weight
• concentration
• pH
• contact time
• substrate composition
• organic matter
• existing chitosanases and chitinases

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

Trials with various fungi showed clear differences. Plant-pathogenic and mycoparasitic fungi were in some cases more sensitive than certain entomopathogenic or nematophagous beneficial fungi.

The field study also does not indicate complete sterilization. It primarily showed a change in 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 in principle 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 form 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 mix mycorrhiza directly into a concentrated chitosan solution
• apply concentrated products at separate times
• test new combinations on a small number of plants first
• avoid 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’s practical experience, we recommend:

• do not prepare chitosan together with MicroBio+ in a concentrated stock solution
• dilute both products separately
• if possible, leave 24 to 48 hours between applications
• only use 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 are fundamentally contradictory.

Chitosan produces a targeted stimulus and influences the rhizosphere. MicroBio+ then 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 can 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 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.

In other plant species, researchers have examined 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 should not be understood as a blanket guarantee for cannabis.

Chitosan may 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 goal.

Foliar treatment

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

Possible advantages:

• direct elicitation of leaf tissue
• uniform distribution with fine spraying
• possible 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 applied 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 defenses
• alteration of root exudates
• influence on the fungal community
• support for a resilient root environment

The biggest mistake here is using too high a dosage.

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

Seeds and cuttings

In various plants, chitosan is also being studied as a seed treatment or during early rooting.

Special caution applies to cannabis cuttings.

Young, not-yet-rooted cuttings have few reserves. At this stage, an overly strong elicitor stimulus may be more likely to hinder than help.

Treatment should therefore be applied only at a very low dosage and initially tested on a small number of cuttings.

When is chitosan particularly interesting for cannabis?

From our perspective, the following timings are especially useful:

Vegetative phase

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

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

After transplanting

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

Immediately after severe root damage, 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 the strong development of flower and resin structures begins.

Controlled elicitation can be particularly interesting here. Foliar treatments should end before the flowers become dense and moisture can no longer dry efficiently.

During mid-flowering

Here, we prefer applications that do not unnecessarily wet developed flowers.

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

Late flowering

During late flowering, you should not try to force more resin in the short term through a strong final treatment.

By this stage, the plant has already completed a large part of its development program.

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

How should chitosan powder be 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 part of the acid.

Demineralized water makes the mixture 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 cautiously and measure the pH.

3. Add the chitosan slowly

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

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

4. Allow time to swell

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 considerably longer than a few minutes.

5. Top up with the remaining water

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

6. Check the final pH

The finished application solution should not be uncontrollably 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 cultivation system must nevertheless be taken into account.

7. Use fresh

Homemade 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 recipe without measurement may be too acidic in soft water and completely inadequate in 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 compounds examined than at 250 mg/L.

The cannabis root studies used considerably 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
• form of chitosan
• molecular weight
• solution
• plant age
• frequency
• cultivar
• cultivation 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 is based on a targeted stimulus.

Continuous or overly frequent application may 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
• leave sufficient time between applications
• do not increase the dosage simply because there is no immediate response
• do not expose plants to several strong elicitors at the same time

Resin formation and metabolic changes are not immediate contact reactions. The plant needs time to respond to the signal.

What should not be mixed with a chitosan stock solution?

Concentrated chitosan solutions can be sensitive to other ingredients.

The following may 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 them in sufficient water
• test miscibility in a small container
• do not use a solution that flocculates or gels
• check the pH before application

Typical chitosan mistakes

Adding the powder directly to tap water

The chitosan floats, clumps or settles. This does not produce a uniform 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 form of chitosan

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, a finished application solution that is too acidic can stress the plant.

Spraying directly onto mature flowers

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

Considering chitosan an acute treatment for every pest

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

Equating chitosan and chitin

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

Promising an increase in THC

The available research does not support such a blanket claim.

Ignoring the soil life completely

In a biological system, chitosan should be used in a controlled manner. Concentrated solutions should not be added directly to live 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 normally used do not make it a conventional nitrogen fertilizer.

Its main effects lie in:

• elicitation
• plant strengthening
• alteration of the defense response
• influence on root exudates
• interaction with microorganisms
• potential influence on 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 genetically absent.

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 habit
• resin gland density
• terpene biosynthesis
• maturation time
• stress response
• hormonal balance
• root development
• susceptibility to pathogens

Different responses should therefore be expected.

What is clearly visible in one cultivar may be considerably 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 due to 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 active Living Soil.

A root application can therefore act relatively directly. Here too, start low and observe the plant’s response.

Organic soil

In organic soil, interactions with humic substances, microorganisms and organic matter also occur.

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 the fungal and bacterial communities must also be considered.

Targeted applications are more sensible than continuously applying 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 glasses when handling acids
• an appropriate dust mask where significant dust is generated
• good ventilation
• slow stirring rather than pouring

CannaSelection chitosan is derived from crab shells.

People with a pronounced crustacean allergy should therefore be particularly careful when handling the dry powder. Even with high purity, production-dependent trace residues cannot be completely ruled out without product-specific analysis.

Always use acids in diluted and controlled form.

Legal classification

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

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

Relevant factors include:

• exact 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 in legal terms.

This article describes the biological properties and the state of research. Actual 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 application and value transparent raw material data.

It enables:

• flexible concentration
• freshly prepared solutions
• foliar or root applications depending on the approach
• 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 match the application method.

Chitosan is not a product for the principle that "more is better."

Used correctly, it is a highly interesting tool for growers who do not simply 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 and industrial hemp.

In addition, CannaSelection observes higher absolute resin quantities 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, well-nourished cannabis plant with a controlled biological stimulus. This may enable it to activate its defenses and specialized metabolism more strongly.

This may be reflected in 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 form of chitosan, a low and appropriate dosage, the correct pH and a suitable 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 production?

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

In the literature we evaluated, there is currently no published cannabis study on the exact absolute resin mass per flower.

Does chitosan improve terpenes?

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

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

Is chitosan the same as chitin?

No.

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

Can chitosan simply be stirred into water?

Normal 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 applied 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. However, targeted measures should still be used in the event of an acute infestation.

Can chitosan cure root rot?

Chitosan can activate root defenses and influence certain pathogens.

It does not automatically cure advanced root disease. 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 exposure.

Can chitosan be sprayed during late flowering?

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

Additional moisture and residues on the final 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.