Cannabis Science

Understanding The Role of Silicon in Plant Health

When most people think about fertilizing plants, they think about the major nutrients like nitrogen, potassium, phosphorus, calcium and magnesium. And there are quite a few other micronutrients that all play important roles in plant health, but arguably there is no other micro-nutrient as important as silicon for optimizing plant health. Silicon plays an integral role in plant health by interacting with several key components of plant stress signaling systems leading to induced resistance. The terminology is confusing because there are differences between silicon, silica, silicic acid and silicate. Sometimes they’re used interchangeably by the fertilizer industry but these terms mean very different things. So, here are the definitions of some common terms involved when talking about silicon in plants.

Silicon: a tetravalent nonmetallic element that occurs combined as the most abundant element next to oxygen in the earth’s crust. It is an element with the symbol Si and atomic number 14. The elemental form itself is unassimilable to plants.

Silica: another name for silicon dioxide (SiO₂); found in the mineral quartz and also a major component of sand. Sometimes you will find products that contain micronized silicon dioxide to be amended in or there is even liquid silicon dioxide as well.

Silicates: compounds containing silicon-oxygen tetrahedrons (SiO4)4-that are used as fertilizers like calcium silicate, potassium silicate, sodium silicate and combinations of diatomaceous earth with minerals.

Silicic Acid: any of various weakly acid substances obtained as gelatinous masses by treating silicates with acids. It is a compound of silicon, oxygen, and hydrogen, regarded as the parent substance from which is derived a large family—the silicates—of minerals, salts, and esters. The only form of silicon which is available for entry or uptake into a plant is silicic acid, Si(OH)4

Monosilicic Acid (MSA): Synonym: orthosilicic acid (OSA). MSA or Si(OH)4 is the simplest form of soluble silicic acid. MSA is found universally in seawater, river water and soils at a concentration of a few ppm. Although MSA is in dynamic equilibrium with disilicic acid, it is considered the only bioavailable form of silicon.

What’s the Difference?

Because most of the silicon in the plant’s crust is held in forms plants cannot take up. These include silicon dioxide (silica) and various silicate minerals. While plants can’t take up silica, they can take up another form of silicon —monosilicic/orthosilicic acid. Bacteria can convert other silicon compounds into monosilicic acid. However, this process takes weeks or months. By the time silicon is in a plant available form, the plant might be too far along in it growth cycle for the silicon to be of much value. Therefore, growers often apply silicon in the form of monosilicic acid.


Potassium silicate (K2SiO3) is a salt of silicic acid (H4SiO4).

As mentioned above, silicates are not available to plants. So, plants cannot take up or use potassium silicate. First, bacteria must convert it to monosilicic acid.

Therefore, applying potassium silicate does not have the same effects as applying monosilicic acid. Depending on the level of nutrient cyclying and silica solubilizing bacteria present in the soil or on the leaf surface (foliar application), your plants will not be able to uptake potassium silicate for potentially weeks, it just depends on a variety of biotic and abiotic factors.

Role of Silicon in Plant Health

Silicon promotes plant growth by increasing the growth of cells which leads to faster growth of the roots stems and shoots. A few studies have shown that the application of silicon yields plants with taller and thicker stems. Silicon also helps protect plants from harmful fungi.

Eventually, silicic acid molecules polymerize into insoluble silica, which is deposited in plant tissues, first in the abaxial (lower) epidermis and then, as the plant grows, in the epidermis. It then condenses into particles of hard, polymerized silica gel, also known as phytoliths. It is this silica that imparts silicon’s benefits to plants by strengthening plant tissues and structures.

Primary Effects on Plant Growth

Mono-silicic acid has three primary effects on plants:

  1. Mechanical – Builds structure and resistance to stress
    Deposits silicon directly into the outer layer of the cell creating a rigid barrier and a more solid structure.
  2. Nutritional – Increased and more balanced uptake of nutrients
    Pressurizes the plant sap to allow a better and more even flow of nutrients throughout the plant circulatory system.
  3. Immunity – Stimulates plant’s immune system
    Triggers the production of immunity compounds, as well as drawing silicon to the point of attack to rebuild and strengthen tissue.

Improves Resistance to Fungal and Bacterial Pathogens

Although it’s not fully known how, silicon helps protect plants against harmful fungi. Some of these fungi include fusarium wilt and powdery mildew. Scientists think one way this element protects plants is by stimulating plant defenses. When you add silicon to your plants, they can better recognize diseases and begin to fight back LINK

Natural Sources of Silicon

So now that we know a little more about the element silicon and its role in plant health, let’s examine where we can find natural source of it.

  1. Diatomaceous earth Diatomaceous earth, also known as diatomite and DE, is the naturally occurring fossilized remains of diatoms—single-celled aquatic algae. It is a near-pure sedimentary deposit consisting almost entirely of silica.
  2. Horsetail The plant horsetail has found extensive application as a source of silica, The results for the silicon concentration in horsetail reached from 2.64% to 4.80% of the dry matter. The lowest amount of silicon was in the range between 1.52% and 2.51%.

Dr. Duke’s Phytochemical and Ethnobotanical Databases provide some reference points to the values of silica and silicon in the plant and shoot tissue of Horsetail – Equisetum arvense (Equisetaceae)

Horsetail Garden Tea

Here is a quick recipe from No Dig Garden for a horsetail extract to apply as a drench or foliar for your plants,

•2 cups fresh horsetail or 1 cup dried

•10 cups water

•Bring to the boil, reduce the heat and simmer for 30 minutes with the lid on. Leave to cool overnight – you may want to pop it outside as it isn’t the nicest of smells and can make the kitchen smell a bit peculiar, not quite what you need first thing in the morning!

•Strain through a sieve or colander lined with muslin and pour into labelled bottles. Store in a cool place for about a month. Pour any leftover potion into a compost heap.

•To use as a foliar spray or soil feed, dilute 1 part horsetail ‘tea’ to 4 parts water.

Here is a recipe for a smaller quantity which can be increased as you wish.

2 cups fresh horsetail or 1 cup dried

10 cups water

Bring to the boil, reduce the heat and simmer for 30 minutes with the lid on. Leave to cool overnight – you may want to pop it outside as it isn’t the nicest of smells and can make the kitchen smell a bit peculiar, not quite what you need first thing in the morning!

Strain through a sieve or colander lined with muslin and pour into labelled bottles. Store in a cool place for about a month. Pour any leftover potion into a compost heap.

To use as a foliar spray or soil feed, dilute 1 part horsetail ‘tea’ to 4 parts water.


In summation, Silicon has been shown to elicit these types of effects on plants

  1. Have stronger and thicker branches by depositing silicon directly into the outer layer of the cell.
  2. Carry sturdier and heavier fruits with higher nutritional value and a longer shelf-life.
  3. Silicon induced thermotolerance – Improves plants tolerance to heat extremes.
  4. Are more resistant to stress caused by high concentrations of salts in the substrate (high EC).
  5. Alleviates abiotic and biotic stresses, and increases the resistance of plants to pathogenic fungi.

Other Research Articles on Silicon

Role of Silicon on Plant–Pathogen Interactions

Silicon Influences Soil Availability and Accumulation of Mineral Nutrients in Various Plant Species

Silicon and plant disease resistance against pathogenic fungi

Silicon-induced thermotolerance in Solanum lycopersicum L. via activation of antioxidant system, heat shock proteins, and endogenous phytohormones

The Effects of Foliar Sprays with Different Silicon Compounds

Agriculture increases the bioavailability of silicon, a beneficial element for crop, in temperate soils


Featured are some of the custom genetics bred by the Cannabis Horticultural Association here in Humboldt County

Banker Plants – 2019 Research Project

Explosive Ember Peppers Intercropped with Cannabis
explosive ember pepper plants

In 2019, the Cannabis Horticultural Association (CHA) embarked on a small research project with Matthew Gates to investigate the use of explosive ember pepper plants in banker plant systems for cannabis. The link to the research information as well a tips on growing and purchasing the peppers is here: EXPLOSIVE EMBER PEPPER PLANTS

Pathogens and Molds Affecting Production and Quality of Cannabis sativa L.

Original Research ARTICLE Front. Plant Sci., 17 October 2019 |

This is a very interesting research article that covers the different pathogens affecting both the root and shoot growth of Cannabis sativa L. Inoculation experiments were conducted on developing buds and the roots of Cannabis sativa to determine the extent of disease development caused by pathogenic fungi. LINK BELOW

Have you had an experience with a pathogenic fungi or bacteria? Let us know about your experience in the comments below.

Cannabis – The Ultimate Modulator

Every once in a while topics outside of horticulture come along that are so important they must be discussed.  I always understood that cannabis modulates (ie: regulates) our bodies through our endo-cannabinoid systems. But I never really understood how extensive it actually was, until now…

In case you’re not aware of it, our bodies have and internal “endo”-Cannabinoid system and cannabis acts as the exo-cannabinoid, “exo” meaning external or outside. So the body has this lock and key system that produces its own endo-cannabinoids and cannabis are like a bunch of keys that are capable of unlocking a lot of locks in our bodies! While this may be an oversimplified version of this system, it’s provides a clear enough analogy to process.

Calcium’s role in Cannabis Physiology

“Calcium is an extremely important plant nutrient due to its many functions, which includes membrane structural integrity, maintenance of homeostasis, segregation of genetic material during cell division, gene expression, energetics and enzyme activities. The full picture of calcium-mediated physiological processes has not been fully described here nor clarified in academic research; however, researchers do know that calcium is immobile in plants and that it is a constant requirement throughout all growth phases.”

Mark June-Wells, Ph.D.

Visit Cannabis Business Times for an interesting article on the roles of Calcium in plant physiology…

The Facts About Dynamic Accumulators


By John Kitsteiner

Within the world of Permaculture we often find reference to plants known as Dynamic Accumulators. In brief, this is the idea that certain plants (often deep-rooted ones) will draw up nutrients from the lower layers of the soil, and these nutrients will be stored in the plants’ leaves. When the leaves fall in autumn and winter and are broken down, those stored nutrients are then incorporated into the upper layers of the soil where other plants will benefit from their deposition….

Read the full article at Permaculture Research Institute.

The Future of Pesticides … Pyrolysis Studies and Separate Classifications for Flowers, Concentrates and Edibles


Accounting to the obscurity regarding the lack of regulation and oversight for the entire modern history of this plant, pesticide testing on cannabis is only now seeing the light of day.  The absence of official federal government rulings has left state regulators scrambling to standardize, monitor and enforce these guidelines on their own. This unfortunately has lead to unavoidable lack of oversight and widespread misuse of unapproved pesticides. Incredibly, the Cannabis Safety Institute has reported “that pesticide residue on retail Cannabis products is often found at levels exceeding the allowable levels on any agricultural product.” This lack of oversight has created an ever-increasing need to understand how long pesticides persist on the plants and what classes of pesticides are considered safe for use.

Plant growth-promoting (PGP) microbes

filamentous bacteria

This article is an excerpt from Springer Open Journal. References are included in original article.

Plant growth-promoting (PGP) microbes are rhizosphere associated organisms that colonize the rhizosphere and rhizoplane and improve plant growth when artificially inoculated onto the seeds or into soil. PGP microbes may promote plant growth either by direct stimulation such as iron chelation, phosphate solubilization, nitrogen fixation and phytohormone production or by indirect stimulation such as suppression of plant pathogens and induction of resistance in host plants against pathogens. The opportunities of PGP microbes include alternating applications of PGP microbes as bio-fungicides with inorganic fungicides to manage fungicide resistance and to reduce the number of fungicide applications per year. PGP microbes also plays an important role in inte-run-off of unused fertilizers and the environment damage that results.

One Bad Apple… Plant Growth Hormones and You

By: Luke A. Besmer

I am sure you’ve heard the old saying about how one bad apple spoils the bunch? Well it’s true, and of all things it’s due to a hormonal imbalance. Who’da thunk? So it turns out that in nature, the first ripe apple of the season drops to the ground and begins to decompose. During the decomposition process, the apple releases a gas called Ethylene. Ethylene is a Plant Growth Hormone (PGH) that triggers the nearby apples to fall to the ground and start the decomposition process. The sweet smell of all those decomposing apples attracts foraging animals who eat the apples and spread the seeds far and wide, often with a little fertilizer to boot (or conversely, to overwhelm scavengers so that some seeds are left undisturbed and able to safely germinate). Ethylene and other Plant Growth Hormones are vitally important to all aspects of plant growth and development, understanding them and their uses can improve any gardener’s yield.

Cannabis Crop Recomendations

By Moriah LaChapelle

Here is a wonderful article [offline as of 1/19/2020] to become familiarized with certain techniques and practices associated with Integrated Pest Management (IPM). 

Moriah LaChapell joined Evergreen Growers Supply during 2015 as an Agronomist. She has a Bachelor of Science Degree in Biology from Western Oregon University and a Professional Viticulture Certificate from Washington State University.  She was previously employed at Fisher Farms as the Plant Health Manager. Most of her work at Fisher Farms involved scouting ornamental plants and releasing beneficial insects to reduce insecticide applications. She is passionate about collaborating with growers to produce long term solutions for pests and plant pathogens. You can contact her directly through her website.

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