Silicon in Plants: Food, Biostimulant or Structural Tool?

Silicon and silicone are different materials. Silicone is a synthetic polymer containing silicon, oxygen and organic groups, whereas plants mainly take up dissolved silicon through roots as orthosilicic acid, H₄SiO₄. Chemical form matters because total silicon content does not establish how much is available for uptake.

Essentiality and beneficial effects

Silicon is not generally classified as an essential nutrient for higher plants. Many plants can complete their life cycle without a demonstrated requirement for silicon, although beneficial responses have been reported under particular growing conditions. The distinction between a requirement and a conditional benefit is explained in Essential and Beneficial Elements: What Do Plants Actually Need?

Research across crops has examined silicon in relation to tissue structure, abiotic stress and interactions with pathogens and herbivores. Outcomes depend on the species, treatment and environment. Describing a silicon-containing product as a biostimulant does not establish its effect; the useful questions concern what was supplied, what the plant took up and which outcomes were measured.

Silicon uptake and deposition in Cannabis

A 2019 study identified two aquaporin proteins in Cannabis sativa with structural characteristics associated with silicon transport. The researchers also detected silicon in hemp tissues, including silica associated with bast-fibre cell walls and the basal cells of leaf trichomes.

The authors interpreted the deposition pattern as evidence for a mechanical role. The observations show that silicon can occur in structural tissues, while the characteristics of candidate transport proteins should not be treated as a complete functional demonstration of their transport activity.

Structural roles and their limits

Following uptake and transport, silicic acid can polymerise into silica associated with cell walls. This can contribute to stiffness and mechanical support in plants, with the extent and location of deposition varying among species and tissues.

In hemp, the observed deposition in bast fibres provides a reason to investigate effects on stem structure. Stronger stems, resistance to mechanical damage and reduced lodging are relevant cultivation outcomes, but their improvement cannot be inferred from deposition alone. Reports of altered stem strength or lignification in other crops also need to be distinguished from direct evidence in a particular Cannabis cultivar.

Silicon and stress responses

Studies across crops have investigated silicon under salinity, drought and metal exposure. Direct hemp research has also examined responses to cadmium, zinc and salinity, providing a more specific basis for discussion than extrapolation from unrelated species.

Cadmium experiments reported changes in uptake or accumulation, water-use efficiency and antioxidant-related responses. One short-term study reported reduced cadmium absorption and increased root-to-shoot translocation without a growth effect in young hemp plants. Reduced absorption should therefore not be described as proof of reduced transfer to every harvested tissue or improved growth.

Under salt stress, research reported mitigatory responses in older hemp leaves alongside silicon accumulation. These findings concern the tested conditions and tissues, not protection from every degree or duration of salinity. The broader distinction between stress exposure, adjustment and damage is discussed in Do Plants Get Stressed Out?

My experience with silicon and calcium

In practical horticulture, I have worked with silicon–calcium combinations where the objective included compact, stocky growth as well as stronger tissues. Those observations are part of my interest in silicon, but combined treatments do not isolate the contribution of either element.

Both elements have roles associated with cell walls, while calcium also participates in signalling. Evidence for these roles does not establish that a silicon–calcium combination consistently restricts cell expansion or replaces a conventional plant growth regulator. My practical observations should therefore be kept separate from a general recommendation for controlling plant architecture.

The questions raised by combined treatments also feature in my account of humic substances, MCT and nutrient uptake. An observed growth response does not, on its own, identify a carrier mechanism or the active contribution of each component.

A Cannabis study using silicate together with phosphite reported a tendency towards shorter branch length. The reported marginal result and the combined formulation make this a research question rather than established evidence that silicon alone controls plant shape.

Chemical form and plant availability

Plants mainly take up silicon as monomeric silicic acid. Products may contain potassium silicate, sodium silicate, stabilized orthosilicic acid, silica particles or other compounds, which can behave differently in solution.

Silicate solutions can be strongly alkaline, and polymerisation or precipitation depends on factors including pH and concentration. Comparing products therefore requires more than a total silicon percentage. The formulation, dilution, solution conditions and amount remaining available to plants all matter.

Interpreting a silicon response

Silicon can occur in structural tissues and has been associated with changes in stress responses and cell-wall biology. Cannabis research supports uptake and deposition, with further experiments addressing particular stresses and formulations.

That evidence does not make silicon universally essential or establish a benefit from every product. A useful evaluation distinguishes tissue accumulation, mechanical performance, stress injury, growth and harvested yield, rather than treating them as interchangeable results.

Product information

For composition and application guidance, see Ortho Origin. Research on silicon or a silicate–phosphite combination does not establish the same effects for this finished formulation.

References

Guerriero, G. et al. (2019). Identification of the aquaporin gene family in Cannabis sativa and evidence for the accumulation of silicon in its tissues. Plant Science, 287, 110167. DOI: 10.1016/j.plantsci.2019.110167.

Luyckx, M. et al. (2017). Silicon and Plants: Current Knowledge and Technological Perspectives. Frontiers in Plant Science, 8, 411. DOI: 10.3389/fpls.2017.00411.

Coskun, D. et al. (2019). The controversies of silicon's role in plant biology. New Phytologist, 221, 67–85. DOI: 10.1111/nph.15343.

Debona, D., Rodrigues, F.A. & Datnoff, L.E. (2017). Silicon's Role in Abiotic and Biotic Plant Stresses. Annual Review of Phytopathology, 55, 85–107. DOI: 10.1146/annurev-phyto-080516-035312.

Luyckx, M. et al. (2021). Silicon reduces cadmium absorption and increases root-to-shoot translocation without impacting growth in young plants of hemp (Cannabis sativa L.) on a short-term basis. Environmental Science and Pollution Research, 28, 37963–37977. DOI: 10.1007/s11356-021-12912-y.

Luyckx, M. et al. (2021). Molecular and Biochemical Insights Into Early Responses of Hemp to Cd and Zn Exposure and the Potential Effect of Si on Stress Response. Frontiers in Plant Science, 12, 711853. DOI: 10.3389/fpls.2021.711853.

Berni, R. et al. (2021). Silicon-induced mitigatory effects in salt-stressed hemp leaves. Physiologia Plantarum, 171, 476–482. DOI: 10.1111/ppl.13097.

Wise, K. et al. (2025). Bioaccumulation of silicon and enhancement of cannabis inflorescence yield from fertiliser supplementation with the biostimulants silicate and phosphite. New Zealand Journal of Crop and Horticultural Science, 53, 1261–1273. DOI: 10.1080/01140671.2024.2339494.

EU Regulation 2019/1009 — Product Function Category 6: Plant Biostimulant.