Many readers may have already heard of the potential benefits of supplementing soil or hydro cannabis plants with silicon in the form of silicates or silicic acid. Some controversy surrounds the true role of silicon in plant metabolism, but a few things we know for sure. Check out the facts and find out if a silicon supplement is really necessary in your garden.
Most plant scientists don’t regard silicon as an essential plant nutrient, mainly because most plants can grow in hydroponic media completely devoid of silicon and turn out to be grade-A crops. Some scientists have predicted that all plants have evolved to have specific cellular silicon transporters just like with other nutrients, suggesting plants must have some uses for silicon. High rates of silicon absorption in rice has lead to a wide acceptance of silicon as an essential nutrient in Japanese agriculture, but the fact remains that most plants in soilless media grow just fine with almost no silicon, so what gives?
Silicon comes in many forms. Silicates, a sort of oxide of silicon, make up around 95 percent of the Earth’s crust and 97 percent of its mantle. Natural soil is rich in silicates and normally provides enough silicon to make plants happy. Silicon absorption by roots is not entirely understood; scientists think that roots absorb and transport silicon in the form of silicic acid.
What role does silicon play in plant health and development? Some research suggests slight growth and yield increases, especially in rice, but the benefits of silicon don’t seem to lie in increased growth and size. Emmanuel Epstein from the University of California Davis proposes that silicon’s main role is in a plant’s defense against extreme climates, drought, pests, pathogens and even metal toxicities.
Silicon helps plants defend against pests by providing them with armor. Much of the silicon that plants absorb gets deposited in the cell walls of leaves, stems and flowers as hydrated amorphous silica, or opal. This mineral makes tissues harder and more difficult to consume by herbivore insects.
Silicon also plays a chemical role in fighting pests in pathogens: it’s involved in the signaling pathways that tell plants to produce more of their own natural insecticides. Without any silicon, different parts of the plant can’t sound the alarm indicating an attack. This has an especially interesting implication for cannabis growers, because it may imply an increase in production of essential oils, though this has not been scientifically demonstrated.
Silicon has been shown to decrease transpiration, which makes plants more resistant to drought. Silicon “reinforcement” in cells also makes them more resistant to extremely high and cold temperatures. Plants supplemented with silicon are also more resistant to extreme conditions of salinity and metal toxicities.
One thing to stress here is that silicon will not likely give a cannabis grower an increase in yield in plants that already grow in pristine conditions. Silicon supplementation may increase plant resistance to disease, fungus, insects and extreme environmental conditions. Increased resistance to stress will certainly help sick plants in a way that makes them yield more, but already healthy plants without silicon will not be too noticeably different from plants with silicon.
If you think a silicon supplement is right for your garden, several options exist for adding some to your soil or nutrient solution. Hydroponic growers may want to invest in silicon’s most water-soluble forms for their nutrients solutions: silicic acid (sometimes in the form of orthosilicic acid) or potassium silicate. Silicic acid is more available, but far more expensive than potassium silicate. Potassium silicate still delivers silicon to plants, but keep in mind it also provides potassium. Follow the manufacturer’s instructions on how much and how frequently to use the supplement, but always use less than recommended. Make sure not to deliver any more than 50 mg / L of silicon in the nutrient solution to the soil or hydroponic media, and don’t spray more than 100 mg / L on the leaves.
Soil growers can also use silicates or silicic acid, but organic options also exist. If you mix your own soil, replace a quarter of the perlite or vermiculite you were already going to add with rice hulls. Rice hulls have a similar moisture holding capacity to perlite, but have no cation-exchange-capacity like vermiculite, meaning they should not completely replace perlite and vermiculite in the mix. Alternatively, a cannabis gardener could also compost rice hulls to make silicon-rich compost perfect for top-dressing soil.