Roses are red, violets are blue, and cannabis is green, or is it? To the uninitiated, the bud of the cannabis plant is always green, because that’s the only way they’ve ever seen it. In the occasional story on the nightly news, and whenever a TV show uses cannabis flowers as a prop, they are always dried, and always green, if they are shown at all. If any of the rest of the plant makes it in the shot at all, it’s only the signature seven-bladed leaf, and always, always green.
However, the cannabis plant has much more variety than that. Like the foliage for which the Northeast is famous, cannabis can be all sorts of colors: purple, pink, yellow, red, even black. Not only can the leaves carry this hue, but the bud can as well.
Colorful cannabis is certainly eye-catching at the dispensary counter, and that effect should not be underestimated. People respond to color at a primal, instinctive level, and make the kind of instinctive reaction that makes marketing experts salivate. Certain strains of cannabis can be grown to accentuate their natural pigment, and if you want to make a name for your brand, it’s a great help if your buds pop with color.
In order to understand this process, it’s important to take a brief trip back to high school biology. You may not remember the class that covered phenotype and genotype, so here’s a quick refresher.
A phenotype is an observable trait in a living organism and one that is genetically determined. So a person with red hair is said to ‘express’ the phenotype of having red hair. That only applies to genetic traits, so if they broke their left knee in a skiing accident, for instance, that isn’t a phenotype.
A genotype is a genetic sequence that could become a phenotype., and you can think of it as the genetic potential of the plant. However, not all genotypes become phenotypes. A person can have the genetic code for red hair but have it overridden by the more ‘dominant’ code for brown hair that they also possess.
So as a grower, what you’re trying to do in influencing color is to encourage a particular phenotype, but that is impossible if the genetics of the plant don’t support it. Color in the cannabis plant is determined by anthocyanins, some 400 different pigment molecules which come in red, blue or purple, depending on their pH.
The ideal pH range for most cannabis plants is between 5.5 and 6.5, but if you use a neutral pH, that will accentuate the blue tones of anthocyanins, bringing out a strong purple color. The best strains for this are ones like Purple Urkle, Grandaddy Purple, and Purple Orangutan. If you push the pH too high, an alkaline pH will produce yellows and oranges, more suited to Wicked OG or Lemon Kush.
Red and pink are highlighted in the Pink Flower Shaman and Predator Pink strains and can be encouraged by with a lower pH and lower temperatures. Keep in mind that this pigmentation is activated in response to the seasons changing, like foliage in the fall, so you may need to stress the plant to get the hue you’re looking for. A phosphorus deficiency can also bring out some red or pink in your plants.
Some strains express all the pigments they can, and these colors meld to become black, Black Willy and Black Tuna for example. While pH and temperature are the go-to tools for affecting flower color, lighting can also play a role. LED lights can be used to highlight certain wavelengths for a spectrum that will stress the plants as well.
Stressing a plant does carry the risk of limiting growth or putting overall plant health in jeopardy, but sometimes a little stress is a long-term benefit. Consider that plants which are watered all the time never develop deep root systems, and are more vulnerable to drought than plants that are encouraged to dig deeper into the soil. If you are cautious and pay close attention to your plants, a little stress can bring out their Sunday best.