Most cannabis buds are green—some more vibrant, others leaning towards yellowish hues. However, The Red Family strains break away from the norm, adopting reddish, purple, violet, or bluish tones. The adjectives "red," "purple," and "blue" spark the curiosity of growers, but the colors in the cannabis plant are not just about aesthetic beauty. They are the expression of a unique group of molecules: anthocyanins. These are also responsible for the pigmentation of many dark fruits and much of the autumnal hues seen in nature.
The purple or violet coloration seen in The Red Family seeds during flowering is due to its high anthocyanin content (from the Greek anthos, flower + kyáneos, blue). These are water-soluble pigments present in plant cells, which produce red, purple, or blue shades in the leaves, flowers, and stems of cannabis plants.
There are hundreds of different anthocyanins, each creating a wide range of colors. For example, malvidin produces purple, flavones generate yellow, delphinidin results in blue, cyanidin gives violet, and pelargonidin creates red and orange. The combination of various anthocyanins in the same tissue, at different concentrations, generates a wide spectrum of intensities, tones, and shades.
Anthocyanins have been found in all tissues of plants, including leaves, stems, roots, flowers, and fruits. In cannabis, they have not been discovered in the roots and are rare in seeds, but in the leaves, stems, and flowers, they can account for up to 2.5% of the plant's dry weight.
It is possible to extract purple and pink resins from the buds of red cannabis. The anthocyanins responsible for the red coloration of the buds are also present within the resin glands (trichomes), resulting in uniquely beautiful extractions.
Dark-colored fruits and vegetables like plums, blackberries, grapes, blueberries, cherries, eggplants, and red cabbage are rich in anthocyanins.
Anthocyanins belong to the flavonoid group (from Latin flavus, yellow), which are secondary metabolites of plants.
There are four classes of flavonoids: flavonoids, isoflavonoids, neoflavonoids, and anthocyanins.
Depending on the species, flavonoids perform various functions in plants, such as:
Not all non-green colors seen in cannabis are due to anthocyanins. In strains that do not produce purple, blue, or red hues, we often see that golden, orange, or yellow tones appear at the end of flowering. These are caused by carotenoids. Carotenoids are pigments naturally present in plant tissues which are typically hidden by the intense green coloration of chlorophyll. When a leaf loses its chlorophyll, it appears yellow because the carotenoids, which were already there, become visible.
With anthocyanins, the process seems different. The plant primarily produces these pigments toward the end of its life. This happens during the final stages of flowering when the days are shortening. At this stage in the cannabis plant's life cycle, chlorophyll production decreases, and the plant channels all its energy into flower and seed production. Meanwhile, anthocyanin production increases. As chlorophyll fades from the plant’s tissues, anthocyanins and other pigments become more visible. It is possible that anthocyanins help the plant cope better with aging, resist damage caused by ultraviolet radiation, and deter herbivores while the seeds mature.
It’s clear that not all cannabis plants turn purple during flowering. What causes this color change, and why does it occur? The answer lies primarily in genetics. The strains in The Red Family collection have undergone hybridization and selective breeding programs to introduce and stabilize the genes responsible for red cannabis coloration, achieving a success rate where 95% of the plants develop purple and reddish hues.
At Sweet Seeds®, we work intensively on selecting parentals to bring these genetics to 100% of individuals with vibrant coloration.
Just like potency, aroma, or bud density, the purple coloration is determined by the genetic makeup of the strain. Historically, most purple or red cannabis were Indica or Indica-dominant hybrids, often containing Afghan or Kush genetics. Their effects were typically relaxing and narcotic, as is common in Indica genetics.
To introduce the red-flowering trait in the first The Red Family seeds, Sweet Seeds® used genetics from Hindu Kush ancestors originating in the Chitral region of Pakistan, near the Afghan border. Today, we are working with other red cannabis strains to expand the genetic pool of our The Red Family collection.
Many strains only produce red weed under specific climatic conditions, particularly when nighttime temperatures are cool. A cool late summer can give outdoor harvests reddish, purple, or bluish tones, while high nighttime temperatures keep the plants green. In colder climates, cannabis plants produce less chlorophyll (the pigment responsible for green coloration in plants), allowing other pigments to become more visible.
Until a few decades ago, red cannabis that retained their color under warm temperatures were rare, but the extensive work of breeders and seed banks has filled this gap. The Red Family seeds display these vibrant colors under all conditions and in nearly all individuals.
In some strains, the purple coloration is limited to the larger leaves, but in The Red Family, even the inner parts of the buds—and sometimes the resin glands themselves—exhibit reddish hues. Macro photographs reveal red filaments developing within the trichomes, showcasing the uniqueness of these strains.
Nutrient deficiencies can also influence plant coloration. The petioles of the leaves (the small stalks that attach them to the stem) may turn purple due to a lack of phosphorus or nitrogen. Similarly, sulfur deficiencies can sometimes cause purple streaks to appear on the stems.
The first requirement for achieving red weed is growing a strain that naturally possesses this trait. Although the exact mechanism behind this phenomenon is not fully understood, it is well-established that there is a strong link between cold temperatures and anthocyanin production in red cannabis. Many strains require cool nights for the purple coloration to emerge and will remain entirely green if temperatures stay warm.
The temperature difference between day and night is another influential factor. When nighttime temperatures drop by more than ten degrees Celsius below daytime temperatures, anthocyanins are more likely to appear, allowing for the desired red weed. Even with strains that turn purple under any temperature—such as those in The Red Family seeds—a more intense coloration can be achieved when nighttime temperatures are low, and daytime temperatures remain high.
Cool nights outdoors can help enhance the coloration of red cannabis plants, but they do not necessarily improve their potency. In fact, cold temperatures generally have a negative impact on THC production.
It is crucial to stop applying nitrogen to the plants during the second half of the flowering stage and to cease all fertilization during the final two weeks. This allows the cannabis plant to use the nutrient reserves stored in its leaves, enhancing the red, purple, and blue hues.
There is a known relationship between pH levels and the color expressed by anthocyanins. The color appears redder under more acidic conditions, bluer under more alkaline conditions, and purple in intermediate pH ranges. Beyond influencing tone, pH may also affect the amount of anthocyanins produced. Studies conducted on fruits suggest that anthocyanin production increases under acidic conditions.
Flavonoids in general, and anthocyanins in particular, feature important pharmacological and therapeutic properties that have incited the interest of scientists. They have shown several properties in in vitro tests. Among other properties, they are antioxidants, antiallergic, antibiotics, anti-inflammatory, neuroprotective and anti-carcinogenic.
Flavonoids could protect against the action of free radicals, oxidizing molecules, ultraviolet radiation, atmospheric pollution and many other pollutants. In theory, taking into account the properties observed in laboratory, the consumption of flavonoids could reduce the risk of cancer, reduce allergic manifestations, relieve arthritis, reduce cholesterol, stimulate the heart, improve circulation, prevent cardiovascular diseases, protect the liver, fight aging, diabetes and obesity and a long list of other benefits, although more research needs to be performed to be able to say it for sure.
Humans ingest flavonoids when eating vegetables and these are likely to be partially responsible for the resulting health benefits of diets rich in fruits and vegetables. Some of the richest foods in anthocyanins, such as blueberries, goji berries or blackberries are considered very beneficial for health, especially for their antioxidant properties.
In studies with rats it has been observed that anthocyanins are able to cross the blood-brain barrier and reach the areas of the brain responsible for learning and memory. It is possible that the presence of anthocyanins may have an impact in the cannabis effects on short-term memory, potentiating or mitigating them.
23 flavonoids and anthocyanins have been found in cannabis and it is known that some of them keep their pharmacological properties in both vapor and smoke forms. Scientists use the entourage effect in order to explain that the pharmacological effects of cannabis are the result of the interaction of the large number of molecules present in the plant. Cannabinoids, especially THC, are primarily responsible for the effect, but terpenes and flavonoids also have an influence. Terpenes and flavonoids are probably responsible for the huge differences in the effects of different varieties that feature similar proportions of cannabinoids. Some anthocyanins feature a determined selective affinity for receptors of the human body’s endocannabinoid system, with some types of junctions with CB1 and CB2 receptors.
The main flavonoids present in cannabis are:
Most of these flavonoids and anthocyanins can present a synergic behaviour working collectively with the cannabinoids and terpenes also present in the cannabis plant, enhancing their effect by acting together. For example, there are cannabinoids, terpenes and flavonoids with anti-inflammatory effects and, without any doubt, the overall effect of several of them, all together, increases the therapeutic effect through synergies and different ways of acting.
Some flavonoids inhibit certain liver enzymes and could influence the pharmacokinetics of THC in the liver and therefore in the perception of the effect of cannabis itself.
