Essential elements

These are nutrients which plants cannot complete their life-cycle if they do not have. Some of those include nitrogen, phosphorus and potassium. There are also non-essential elements that provide certain benefits to some plants. Silicon, which we’ll look at in this article, is an important but often overlooked component to plant health and growth.


Is the second most abundant element in the earth’s crust and is found in significant quantities in the soil; however, silicon can only be taken up by the plant in the form of mono-silicic acid. Although vital to plant health, silicon 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 regiment.

What Benefits Does Silicon Provide for Plants?

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

Stronger cell walls

Silicon 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 silicon 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.

Increased resistance to environmental stress

Since plants lack the immune system that animals rely on to stay healthy, silicon 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 silicon 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: Silicon 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 silicon, the plant accumulates the silicon 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 silicon 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

    Silicon 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 silicon gets directly absorbed into the leaves where it can be immediately used to combat pests.

    Enhanced metabolic functions

    Plants grown with the use of soluble silicon 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.

    When Should Silicon be used?

    Studies show that silicon should be used throughout the entire life cycle of the plant, from the seedling or clone stage up until harvest. In order to produce optimal results, silicon needs to be continually made available to the plant via the nutrient solution. Once a plant has absorbed the available silicon 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 silicon that may be present in the soil, whereas plants grown hydroponically have no direct source of silicon unless it is added as a supplement to the nutrient regiment. Plants grown hydroponically without silicon will most likely be sub par compared to those grown with it. Cuttings and seedlings that have been fed silicon tend to show less shock during root formation and transplanting. Introducing silicon early on in the plant’s life is also said to reduce the chances of leaf curl. Cut flowers also benefit from silicon, 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 silicon!

    How Should Silicon 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 silicon 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 silicon 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. Silicon is also known to prevent powdery mildew when used as a foliar spray. If using silicon 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. Silicon is alkaline by nature and therefore will naturally raise the pH level of your nutrient solution, however, there are silicon products on the market that will not affect the pH. It should be added after the other nutrients have been thoroughly mixed into the water. It is a good idea to dilute the silicon in about one gallon (3.79L) 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, silicon may raise the pH level of the solution enough that the additional use of pH up products will not be necessary.

    What Types of Silicon are the best?

    Since there are so many brands of silicon 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 silicon. Look for brands that have at least 7 to 8% silicon dioxide. Liquid silicon 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 colourants. 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 labelling 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 silicon as a super supplement in your next grow!

    The Main Types of Silicon

    The two main types of Silicon we have at Straight Up Hydroponics are Potassium Silicate and Silicic Acid.
    Potassium Silicate
    In horticulture, potassium silicate is used as a soluble source of potassium and silicon. It makes the growing medium more alkaline. It is also used as a supplement (in conjunction with normal fertiliser) for the numerous benefits that increasing the availability of silicon compounds has. Silicon-containing compounds are valuable to a plant, and serve to support the plant. Stems thicken, the plant becomes more tolerant to drought and resists wilting, and the plant gets larger leaves and fruit (because the stem can support more weight). The thicker cell walls of the plant also provides an added mechanical resistance to sap sucking insects (e.g. spider mite) and various pathogenic fungi (e.g. powdery mildew).
    Silicic Acid
    Silicon is everywhere but is generally unavailable to plants. In nature, microbes convert unavailable forms of silicon into (mono)silicic acid – the only bioavailable form of silicon. This process is slow and depends on many factors. That means a grower may add silicon additives but not experience the true power of growing with silicon. So, in its most common forms silicon is not readily absorbed into biological tissues. Take potassium silicates as an example. Its molecules are too large to penetrate our plants cell walls. Microbes will have to convert it into silicic acid before the roots can take up the silicon. This process is called silicification, and it can take weeks or months before it occurs in any meaningful amount. For most applications however, speed and bioavailability are critical. Crops are often harvested in a matter of weeks or a couple months, after which growing substrates are often discarded or sterilized. This destroys the micro-life populations and minimises the silicification process. Silicic acid is therefore the most effective silicon additive since it’s 100% bioavailable. In order for plants to use silicic acid it must be in monomer form (single molecule, mono-silicic acid).

    Cost of Silicon

    The cost of silicon would be dependant on the type of silicon you would like to add to your feed, if you wanted to go for the potassium silicates that takes time to be absorbed by your plant and will likely raise the pH level you can look at paying £4 for 250ml up to £37 for 5L depending on the brand. But, if you wanted to get one of the silicic acids that are less likely to raise pH levels and are immediately available to the plant you could be looking to pay from £22.50 up to £600 depending on size and brand.