Why Your Plants Need More Silica

By Helene Isbell
Published: January 28, 2021 | Last updated: April 20, 2021 09:21:26
Key Takeaways

Even though it isn’t classified as an essential plant nutrient, silica is an important player in the growroom. In fact, you could say silica is the jack of all trades in the plant kingdom.

Silica plays an important role in just about everything.

  • It is one of the main components of the Earth’s crust
  • It makes up the sandy beaches that border the oceans of the planet
  • It lies in the veins of quartz crystal that course through granite boulders
  • It is used to make the glass products that we use in our everyday lives on a regular basis

Silica, often renowned for its rigid properties, is also an important component of the plant kingdom, a jack of all trades in the horticulture hemisphere.

Pile of white silica sandPile of white silica sand. Source: Anton_Starikov/Shutterstock


What is Silica?

Silica is the common term for the compound silicon dioxide. It is formed when silicon comes into contact with oxygen.

Silica is abundant in many soils and is a major component of plant tissue, sometimes in even higher concentrations than nitrogen and potassium – two out of the three primary macronutrients.

Although vital to plant health, silica is not classified as one of the essential nutrients for plants in general, which can lead some growers to believe it is not necessary to add to a normal feeding regimen.


Read also: The Many Ways to Use Diatomaceous Earth in the Garden

Plant leaf cell wall under microscope and closeup of plant stemsBenefits of silica include stronger cell walls and thicker plant stems. Source: Shutterstock


What Benefits Does Silica Provide for Plants?

The list of benefits that silica provides to plant health is lengthy. Any grower who is serious about growing strong beastly plants should consider adding silica to their normal fertilization schedule. Some of the most important benefits are:

Stronger cell walls

Silica can be compared to the likes of a liquid bamboo, virtually fortifying cells from the inside out. Cells are the building blocks of the plant's framework. Strengthening the cell walls helps the plant build strong hearty branches and stems that are reinforced enough to support the weight of the fruit that the plant will eventually produce.

Stronger cells mean bigger stems

Thicker cell walls resulting from silica use create bigger stalks and stems that can uptake and transport more water, nutrients, and plant secretions throughout the plant body, facilitating faster growth rates and bigger plants.

Read also: Optimizing Climate in Your Greenhouse

Increased resistance to environmental stress

Since plants lack the immune system that animals rely on to stay healthy, silica helps perform many of the same functions and can be thought of as a super vitamin and an immune support for plants. It contributes to areas such as:

  • Climate: The addition of silica helps plants withstand extreme temperatures, whether hot or cold. This is especially helpful for outdoor growers that experience hot midday peaks or low temperatures at night.
  • Drought: Silica forms a protective coating on an intracellular level that decreases the amount of water loss through transpiration, making plants less likely to suffer as dramatically during drought conditions. It also enables them to continue functioning during high-temperature or low-moisture conditions and reduces the amount of shock they experience in such extreme cases.

Increased resistance to pathogens

When a plant is fed a soluble form of silica, the plant accumulates the silica around the infected site forming selectively fortified areas that can fend off fungal infections such as rust, pythium and powdery mildew.

As a resistance measure, the plant uses the silica to build up an additional mineral barrier, essentially lining the cells, making it more difficult for diseases and plant pathogens to make their way inside the plant.

Increased resistance to pests

Silica accumulates in the epidermal cell walls of leaves, making it harder for biting and sucking bugs to damage the plant. Deposits of silicic acid within the cells act as an additional barrier to sap sucking insects. Foliar feeding is the best way to ensure the silica gets directly absorbed into the leaves where it can be immediately used to combat pests.

Read also: The Do's and Don'ts of Foliar Feeding

Enhanced metabolic functions

Plants grown with the use of soluble silica are shown to have higher concentrations of chlorophyll in their leaf tissue compared to plants grown without it. It also enables them to make more efficient use of carbon dioxide (CO2), resulting in lush healthy green foliage with excellent leaf structure and reduced amount of leaf wilt.

Foliar spray on seedlingsSilica can be applied as a foliar spray. Source: Yamelahz/Shutterstock

When Should Silica be used in the Garden?

Studies show that silica should be used throughout the entirelife cycle of the plant, from the seedling or clone stage up until harvest. In order to produce optimal results, silica needs to be continually made available to the plant via the nutrient solution.

Once a plant has absorbed the available silica into its cellular structure, it can no longer be redistributed to other parts of the plant.

Plants grown in soil are more likely to uptake trace amounts of silica that may be present in the soil, whereas plants grown hydroponically have no direct source of silica unless it is added as a supplement to the nutrient regimen.

Plants grown hydroponically without silica will most likely be sub par compared to those grown with it.

Cuttings and seedlings that have been fed silica tend to show less shock during root formation and transplanting. Introducing silica early on in the plant’s life is also said to reduce the chances of leaf curl.

Cut flowers also benefit from silica, as it has been known to extend flower shelf life. Have you ever added a powder sachet into the vase of water when you buy a bouquet of flowers? That is a nutrient mixture combined with silica!

Nutrient mixture with Silica added to vase for cut flowersNutrient mixture with silica added to vase to increase shelf life of cut flowers. Source: FotoHelin/Shutterstock

How Should Silica be Applied to Plants?

It’s a good idea to follow the dosage rates of the particular product being used, but as a good rule of thumb, when plants are very young, introduce silica at about 20 to 30% of the general feeding rate and gradually increase the application as the plants grow in size and enter the bloom phase.

Most silica products on the market can be applied as a root feed or as a foliar spray. Plants can absorb much more through foliar feeding than just absorption through the root zone.

Silica is also known to prevent powdery mildew when used as a foliar spray. If using silica as both a foliar and a root feed, be careful not to overdose the plants. Follow the feeding schedule according to the brand carefully before mixing the solution.

Read also: Dealing with Powdery Mildew

Silica is alkaline by nature and therefore will naturally raise the pH level of your nutrient solution. It should be added after the other nutrients have been thoroughly mixed into the water.

It is a good idea to dilute the silica in about one gallon of water before adding it to the reservoir to avoid nutrient lockout that may occur when it comes into direct contact with other elements in the solution.

In many cases, silica may raise the pH level of the solution enough that the additional use of pH up products will not be necessary.

What Types of Silica are the Best for the Garden?

Since there are so many brands of silica in the horticulture industry, it may be tough to decide which one to use. It is wise to choose one with a high concentration of silicon dioxide so that a little bit goes a lot further.

There are brands that boast fancy labels and high-sticker prices but then only provide products that contain 3% or less concentration of silica. Look for brands that have at least 7 to 8% silicon dioxide.

Liquid silica that is clear will be more soluble in the reservoir than those types that have a milky, chalky consistency. Remember to choose products that are free of dyes or colorants.

In the world of hydroponics and gardening in general, the sheer amount of products on the market can be daunting. There are many secret recipes, mysterious formulas, cryptic ingredients, and vague labeling to contend with.

Once in a while it’s nice to fall back on a basic product that is easy to understand, is even easier to use and produces great results.

When one product has a seemingly endless list of positive attributes, it’s a no-brainer that it should be put to use by growers that are serious about producing results. For robust crops and impressively healthy harvests, try silica as a super supplement in your next grow!

Read next: Building Up the Brix for Healthier Nutrient Dense Crops


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Written by Helene Isbell | Sales Representative

Profile Picture of Helene Isbell

Helene Isbell has a passion for plants. She has also been a dynamic player in the hydroponics industry for the past decade. She has incorporated her love of horticulture with hands-on experience, arts and culture, integrated marketing and education.

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