What good are cannabis flowers with no trichomes or terpenes? Sure, other parts of the plant can be used for a variety of industrial purposes, but the most valuable parts of the plant aren’t found in the fibers or vegetative parts — they’re found within the glandular trichomes of the flowers, in the form of terpenes.
Cannabis growers are really terpene farmers, whether they are in the medical or recreational industries. Terpenes provide therapeutic and pharmacological qualities for patients with medical needs. They also set the standard for quality in the recreational industry, driving pricing decisions on a daily basis. And calcium is required for the formation of trichomes and their secretion, as well as playing a critical role in disease resistance. Powdery mildew outbreaks in the late stages of flowering can be a reflection of major calcium deficiencies.
First, let me ruffle some feathers and address the elephant in the room: calcium is mobile. The notion that calcium is immobile is a commonly held misconception that arises from the complexity of how calcium is used by plants. In reality, it is mobile, and its mobility has long held the fascination of botanists for its special place in plant metabolism due to its dual role as a signaling element and a structural element.
Calcium moves in waves through plants, acting like a spark. As it flows through each cell, it functions as a signaling element that spreads messages across the whole plant. These waves form unique patterns, and it is within these patterns that calcium signals induce an enormously broad range of primary and secondary functions in plants — everything from circadian rhythms, sugar metabolism, photosynthesis, transpiration, responses to every type of stress a plant can experience and much more. The holy grail of research in this field is finding ways to decode these cryptic spatial and temporal calcium-encoded messages.
Its role as both a signaling element and a structural element is precisely why it has fascinated researchers for decades. There is so much to learn, particularly at the interface where the signaling and structural roles overlap. One such example would be in the cell walls of plants.
Calcium affords mechanical and physical properties as a structural component of cell walls. This helps plants resist disease pressures such as powdery mildew. With inadequate supplies of calcium, cell walls become thin and weak, which makes it easier for molds to infect plants. In this way, powdery mildew outbreaks can be signs of calcium deficiencies, and growers who are always struggling to combat molds and mildews in the mid to late stages of flowering should look at ways to increase calcium levels in their feedwater.
But more importantly, it also plays an analogous role in the cells of glandular trichomes. Calcium is critical for their formation on the leaf surface and subsequent growth upward. The accumulation of terpenes in the bulbous heads of glandular trichomes is a phenomenon driven by calcium because of the way it interacts with the DNA of a plant to achieve the production of secondary metabolites. These require trichomes, and trichomes require calcium. In this way, calcium both stimulates and participates in the production of trichomes and terpenes. This beautiful dynamic between signaling element and structural compound is unique to calcium in the context of terpene farming, and it’s a critical component of achieving high-quality yields that most growers unfortunately overlook.
As cannabis plants flower, the production of trichomes requires more calcium, rather than less, so it’s ironic that most fertilizer programs — whether they are put together by growers, consultants or manufacturers of fertilizer themselves — tend to cut out calcium far too early. It’s no wonder that so many gardens struggle with pests and disease pressures in the mid to late stages of flowering: the entire industry is chronically deficient in calcium.
Across the full lifespan of the plant, calcium contributes to its physical and chemical defense systems. There is a profound relationship between the amount of calcium that is available for plants to utilize and their ability to defend themselves against stressors and disease pressures — and this includes through the formation of thicker cell walls and the production of glandular trichomes along with the secondary metabolites that fill their bulbous heads.
With enough calcium, a plant will be able to make exceptionally robust and thick cell walls that are more than capable of resisting most mechanical and environmental stressors. It will also be able to sufficiently form the trichomes that contain the specialized metabolites that further serve as a chemical defense against biological stressors.
The less calcium plants have, the fewer trichomes and terpenes they will be capable of making. As calcium levels continue to deplete, the integrity and structure of cell walls is compromised, and the outbreaks of powdery mildew can be catastrophic.
Scenarios like this are far too common in the industry but are entirely avoidable if growers focus on the importance of calcium in flowering. Commercial growers who are not increasing calcium levels progressively during early, mid and late flowering stages could be leaving a lot of potential on the table and inviting disease pressures into their garden.