Cannabis strains, long before cannabinoid testing, could only be measured with the senses. How did it smell & taste? Bag appeal came from the bud trim and aromas, sure. But what really blows us away every time is color. 93% of shoppers make purchasing decisions based on color and visual appeal. And nothing says “WOW” like some green that isn’t green. So where do those amazing bud colors come from?
A thing to remember is that there are four different parts of your plant which are capable of producing marvelous colors.
As you probably know, calyxes make the buds. Indeed, the buds you hold in your hand are a combination of several hundred calyxes piled on top of one another, and some, or all, of them, can become a color aside from green. It is the calyxes that provide the most color in your buds. Obviously, the greater the number of colorful calyxes, the more vibrant the color of the bud.
The pistils, or hairs, that stick out of the buds often turn orange, red, purple or pink; even if the buds and leaves stay green. After the buds are dried, they retain some of the pistil colorings, and you’ll also see some of the color looking to get through beneath the buds.
In certain strains, the buds stay green while the leaves change color. The result is a stunning plant, but as leaves tend to be trimmed after harvest, you won’t see much of the color on the buds. It is possible for the buds to remain the same while the leaves turn purple, for example. This phenomenon can happen when your plants are exposed to low nighttime temperatures. The leaves exposed to light turn purple while those in the shade don’t change color.
Experienced growers often use the ‘trichome’ method to determine when a crop is ready for harvest. Using a magnifying glass, they know that clear trichomes mean the plant isn’t ready. If the trichomes are milky white, the plant is at its highest THC content and prime for harvest. If the color changes to amber or yellow, you must harvest immediately, and the weed will provide a mellow high.
In rare cases, trichomes can turn pink or purple, which makes it hard to determine when to harvest. At this stage, the pistil method comes in handy.
How Do Genetics Influence Cannabis’s Color?
In order for plants to express vibrant non-green hues, they may need the genetic building blocks to do so. These building blocks are called anthocyanins, which are a family of flavonoids that provide purple, red, or blue pigments (also found in blueberries, eggplants, red cabbage, concord grapes, violets, and other richly-colored plants). Some cannabis strains naturally contain higher levels of anthocyanins than others. Ever notice some of your favorite strains tend to express the same colors over and over again? Granddaddy Purple, for example, seems to always carry swirls of deep purples and pastel lavenders. This alternative coloration is indicative of the strain’s predisposition to high anthocyanin levels, and it’s certainly a quality some cannabis breeders attempt to select for and coerce, if only to make us consumers ooh-and-ahh over pretty colors (hence the long line of “purple” strains that includes Purple Kush, Mendocino Purps, Purple Urkle, and many others).
Which Cannabis Strains Tend to Turn Purple, Blue, and Red?
There are many strains that contain a genetic predisposition for high anthocyanin levels, and you’ll often find them under monikers that begin with colors like purple, red, blue, or pink. No, this doesn’t mean these strains will always show off fancy hues, but they have a higher potential of doing so if conditions are right.
Plants with low anthocyanin may produce a different array of colors in the final weeks of flowering, due to another family of molecules calledcarotenoids. These are responsible for the earthy gold and yellow hues buds can take on before harvest as chlorophyll shuts off.
How Does Cannabis Go from Green to Purple?
As you might remember from your elementary biology classes, chlorophyll is what gives plants its green color. Chlorophyll is vitally important to the photosynthesis process by which plants absorb sunlight for energy. As cannabis plants mature, they produce less of the dominant pigment chlorophyll and we begin to see those anthocyanins emerge in a show of purples, reds, and blues. Growers should note that there are specific environmental conditions that trigger the halt of chlorophyll production. We’ll get into that shortly.
What Other Environmental Factors Affect Cannabis’s Color?
Although not all cannabis strains will express purple, blue, or red hues in their lifetime, those equipped with the right genetics may do so under certain environmental conditions. The reason why cannabis produces flavonoids and anthocyanin, researchers have observed, is for protection. Information on anthocyanin production in cannabis is limited. What we do know comes largely from cannabis cultivation experience and studies measuring patterns of anthocyanin production in other vegetation.
First, there’s temperature. Purple, red, and blue hues may appear in response to drops in temperature, since chlorophyll production takes its natural pause in autumn as the days become colder. Research on other fruits and flowers noted that higher temperatures destroy anthocyanin production. That same study also found that higher pH levels lead to the destruction of anthocyanin pigments, meaning they tend to thrive in more acidic environments.
The pH level determines which pigment the plant takes on:
- Acidic environments tend to induce red and pink coloration
- Purple coloration occurs in neutral pH environments
- Blues become present with higher pH levels
- Yellow is developed in alkaline conditions
Are Purple Cannabis Strains More Potent?
They might be more eye-catching, but purple strains are not necessarily more potent than their green relatives. A purple-blossomed plant exposed to cold temperature may actually produce less THC, so it’s important to keep in mind that “many traits prove to be desirable only in certain varieties under certain conditions.”
What is the Color Spectrum of Light?
Although natural light might appear white to us, it is actually made up of many different colors. You can see this in action when you put light through a prism, or if you catch the sight of a rainbow. When light is refracted into its individual parts, you can see all the colors that make up that light!
Over the years, we’ve learned that plants actually make “decisions” about how to grow based on the spectrum of light they receive. A different color spectrum can change how cannabis germinates, grows and even makes buds! Although we don’t have a lot of options to change the spectrum of sunlight when growing outdoors, we have almost complete control of the spectrum when growing cannabis indoors since we’re using grow lights!
As just one example, during the spring and summer, more of the blue spectrum of light makes it to earth because the sun takes a more direct path through the sky.
In the summer, a plant responds to this bright direct light (with lots of blue) as a cue to grow vegetatively with lots of big leaves and short stems. The plant tries to spread out as much as it can and increase its leaf mass.
Blue light – Grow lights with a higher ratio of blue light are often used in the vegetative stage as they tend to make cannabis plants grow short and squat, with big healthy leaves.
As fall approaches the sun starts hanging lower in the sky. As a result, more of the light that reaches the plant falls within the red spectrum. More light in the red part of the spectrum is a sign to the plant that summer is coming to an end and it’s time to get in gear before winter. As a cannabis plant gets exposed to a higher ratio of red light, it reacts by growing longer stems with more space between the leaves, getting as tall as possible for the best position to start making buds and pollinate via the wind!
Yellow/Red light – Grow lights with higher amounts of red are often using in the flowering stage to encourage plants to grow tall (stretch) and to help promote budding. Plants may switch to the flowering stage faster under red light than under blue.
How big a difference does spectrum make to plant growth?
As long as a cannabis plant is getting bright light with at least some red and blue, it will grow normally, so any reputable plant grow light you get on the market will do the job and get you to harvest with top-quality buds!
[Updated, originally published 12.2.2017]
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