How Silicon Promotes Plant Growth

Although silicon is not considered an essential nutrient—plants can grow without it—it significantly boosts plant strength and stress resistance. For cannabis, silicon contributes to development of the terpenes and phenolic compounds that growers prize. Here’s why supplementing your feeding program with silicon might be beneficial.

Benefits of silicon

Silicon improves plant health and growth in several important ways.

Physically, this beneficial nutrient help plants form a strong layer of hydrated amorphous silica, or opal, in their cell walls. This silica layer acts as a mechanical barrier that provides many benefits to cannabis, including:

  • Protecting against pathogen infections
  • Heightening resistance to sucking insects
  • Reducing water loss and enhancing photosynthesis[1]
  • Reducing abiotic stress from environmental factors like salinity and drought[2]

Additionally, silicon fortifies stalks and stems, so plants can support weighty CBD- and THC-rich fruits and flowers, and delays plant aging, or senescence.

Chemically, silicon helps plants defend themselves by promoting the biosynthesis of compounds that protect against biotic stressors. These secondary metabolites include terpenoids, alkaloids and various phenolic compounds, which are either repellant or toxic to biotic attackers.

Plants also produce a blend of phytohormones, or growth-regulating compounds—including salicylic acid, jasmonic acid and ethylene—and research finds that silicon plays a critical role in multiple phytohormone signaling pathways that alleviate biotic stress.[3]

Finally, silicon helps alleviate metal toxicity[4] and improves the availability of other essential and beneficial nutrients, including calcium, magnesium and zinc.[5]

Figure 1. How silicon alleviates stress and boosts plant defenses. Source: Etesami, Hassan, and Byoung Ryong Jeong. 2018. “Silicon (Si): Review and future prospects on the action mechanisms in alleviating biotic and abiotic stresses in plants.” Ecotoxicology and Environmental Safety 147: 881-896.

Silicon shields rice: a case study

We can see how much of a difference silicon makes in a study on rice resistance to a fungal disease known as rice blast.

Researchers found that rice plants supplied with a single dose of silicon immediately after pathogen inoculation or treated continuously with silicon for their entire life cycles had disease severity indices of 20.8% and 19.6%, respectively—significantly lower than the control rice untreated with silicon, which had a disease severity index of 63.7%.[6]

As illustrated in the photo below, the silicon-treated rice formed a hard, protective silica gel on its epidermal surface, as well as in the vascular tissues of its stem, that prevented the fungal pathogen from penetrating its cell walls.

Figure 2. The top photo shows rice 10 days after it was inoculated with the disease known as rice blast. Rice plants on the right were continuously treated with silicon, while those on the left were untreated. The bottom graphic explains how silicon-treated rice were able to form a silica layer that prevented the fungi from penetrating the plant’s epidermal cells. Source: Wang, Min, Limin Gao, Suyue Dong, Yuming Sun, Qirong Shen, and Shiwei Guo. 2017. “Role of Silicon on Plant–Pathogen Interactions.” Front. Plant Sci. 8.

Fertlizing with silicon

While silicon is the second most abundant element in the soil after oxygen, it is not naturally present in a plant-accessible form. In fact, silicon is never found in a “free,” water-soluble form; it is always combined with other elements, forming oxides or silicates.

The only silicon compound that plants can take up is uncharged silicic acid, which is the sole water-soluble form of the beneficial nutrient. However, despite what some nutrient companies claim, you won’t find a silicic acid fertilizer because it is highly unstable. If bottled in a solution of more than 100 to 200 ppm, silicic acid will precipitate and revert to grainy silica—sand, basically.

To fertilize a crop with silicon, it must be in the form of a silicate—a compound containing a silicon atom and an oxygen atom. Soluble silicates are usually combined with other elements, such as potassium, calcium or magnesium.

For example, Emerald Harvest’s Sturdy Stalk is a potassium silicate supplement that combines the plant-strengthening benefits of silicon with bloom-boosting potassium, so cannabis crops obtain higher yields and are sturdy enough to support heavy buds.

Stay tuned for our next blog post with more information on plant-available silicon sources. For an in-depth explanation of how to use silicon supplements and why they benefit cannabis, check out our white paper Inside Silicon Supplements: Making Sense of What’s Inside the Bottle.

The Emerald Harvest Team

[1] Specifically, it helps reduce water loss from perspiration while maintaining greater stomatal conductance, which optimizes photosynthetic efficiency.

[2] Curry, Heather A. and Carole C. Perry. 2007. “Silica in Plants: Biological, Biochemical and Chemical Studies.” Annals of Botany 100 (7): 1383-1389. https//

[3] Frew, Andrew, Leslie A Weston, Olivia L Reynolds, and Geoff M Gurr. 2018. “The role of silicon in plant biology: a paradigm shift in research approach.” Annals of Botany 121 (7): 1265-1273.

[4] See footnote 1.

[5] Greger, Maria, Tommy Landberg, and Marek Vaculík. 2018. “Silicon Influences Soil Availability and Accumulation of Mineral Nutrients in Various Plant Species.” Plants 7 (2), 41.

[6] Sun, Wanchun, Jie Zhang, Qionghua Fan, Gaofeng Xue, Zhaojun Li, and Yongchao Liang. 2010. “Silicon-enhanced resistance to rice blast is attributed to silicon-mediated defence resistance and its role as physical barrier.” Eur J Plant Pathol 128: 39-49.

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