Seedsman Blog

From Purple Pot To Blue Bud: Why Cannabis Comes In Different Colours

With names like Purple Punch, Pink Panther and Lemon Kush, many of the most popular cannabis cultivars offer an eye-catching departure from the typical green coloration that is generally associated with marijuana. And while the uninitiated may be surprised to learn that not all varieties of bud are entirely verdant, any experienced cannabis connoisseur knows that there’s a riot of colour to choose from.

This is largely thanks to the work of some dedicated and talented breeders, who have helped to refine the genetics and develop the growing techniques that are necessary to bring out the many tones and hues that are present in marijuana. Welcome to the colourful world of cannabis.

Reds, Purples and Blues

The red, purple and blue tones that predominate in certain strains are produced by pigmented compounds called anthocyanins, which are a type of flavonoid. Also found in blueberries, aubergines and an array of other plants, anthocyanins are known for their antioxidant, anti-inflammatory and anti-bacterial properties, and as such are often present in so-called superfoods[i].

Certain cannabis cultivars are genetically predisposed to contain high levels of anthocyanins, which means they have the potential to express a range of different pigments. However, the intensity of these tones is always influenced by environmental conditions, so there’s a fair amount of work for a grower to do in order to bring out the colour of these flavonoids.

Generally speaking, these hues won’t be visible until fairly late in the flowering stage, as plants continue to produce chlorophyll in order to photosynthesise throughout their development, and therefore appear green. Yet as the temperature drops in autumn, mature cannabis plants naturally cease their production of chlorophyll and devote more of their energy to the development of cannabinoids, terpenes and flavonoids in their flowers, all of which allows the colour of the anthocyanins to shine through.

Experienced growers therefore manipulate temperature in order to encourage their plants to maximise their production of anthocyanins during flowering. If heat levels remain constant then plants may simply continue to generate chlorophyll, and will therefore continue to appear green, but dropping the temperature ever so slightly at night can result in significant colour changes.

It’s a fine balancing act to get this right, though, as temperatures that are too cold can cause a plant to go into shock or to limit its production of cannabinoids, so plenty of experience is required in order to pull this off. Some strains – including Purple Orangutan – have extremely high anthocyanin levels and can therefore develop an intense purple pigmentation even if temperatures are not tweaked, making them more suitable for beginners who want to start growing purple weed.

Another factor that greatly affects the pigment of anthocyanins is pH. In general, cannabis likes to grow in soil that is fairly neutral, with a pH of between 6.0 and 7.0, but slight changes to this can alter the tones that appear in the final product. For instance, anthocyanins tend to appear red in acidic conditions, so strains like Red Dragon and Pink Flower Shaman are grown in soil with a pH that is towards the lower end of the optimal range.

Blue cannabis cultivars owe their colour to their high levels of anthocyanins

Purple colours, meanwhile, tend to come out when the pH is more neutral and blue tones are expressed with slightly more alkaline soils that have an elevated pH.

While research on the function on anthocyanins is limited, they are thought play a number of important roles that aid plants in their development. Among other things, they are believed to help protect plants from certain light wavelengths, ensuring they don’t become damaged by the sun’s radiation, while the colours they create tend to attract pollinating insects like bees.

Yellows, Golds and Oranges

While not all cannabis strains have the genetics to produce high levels of anthocyanins, many can still change colour once they stop producing chlorophyll, thanks to the presence of another family of pigments called carotenoids. Also found in carrots and pumpkins, these compounds are responsible for the golden hues that many plants take on during the autumn months, and are also an important component of a healthy diet. If you’ve ever been told that eating carrots helps you to see in the dark, it’s because they contain certain carotenoids that the body requires in order to synthesize vitamin A, which is important for vision and growth.

As with anthocyanins, carotenoid pigments only become visible during the latter stages of flowering in cannabis plants, when the reduction in chlorophyll levels allows colours other than green to take over. Certain strains are genetically predisposed to produce higher concentrations of carotenoids than others, although environmental conditions are once again crucial to determining how intensely these colours are expressed.

For this reason, cultivars like Orange Bud, Olive Oyl and others are typically grown in alkaline soils, as the citrusy hues produced by carotenoids tend to become more visible at higher pH levels. It’s also worth mentioning at this point that some growers try to cheat their way to more colourful weed by depriving their plants of certain key nutrients. Nitrogen deficiency, for example, can result in yellowish bud, while a lack of phosphorous produces a red tinge. Obviously, these plants will always be of a low quality and while they can sometimes look striking, they are never as beautiful as those that gain their colour from natural pigments.

In terms of function, carotenoids help plants to absorb light for photosynthesis while also acting as antioxidants. Studies have shown that people who ingest high levels of carotenoids in their diet tend to benefit from greater protection against sunburn[ii], proving that these cheery pigments offer much more than just pretty colours.

What About Those Super Strong Blacks?

Some cultivars that are derived from Vietnamese landraces have become known for their extremely dark pigmentation and intense psychedelic effects. The colouration of Vietnamese Black and other related strains is caused by an extremely high genetic predisposition for anthocyanin, which becomes so abundant that the leaves and flowers take on a deep purple tone that appears black.

It’s important to recognise, however, that the potency of these cultivars has absolutely nothing to do with their colour, as anthocyanins do not influence the strength of the effect produced by a plant. However, because these richly pigmented cultivars have become associated with the intense highs that they produce, many people have erroneously come to believe that a plant’s colour is an indication of its strength.

To be clear, this is absolutely not the case, and as more and more beautifully tinted cultivars hit the market it’s becoming increasingly necessary to dispel the myth that darker plants are more psychoactive. Still, there is a value in beauty, and the trippy colours that embellish certain cannabis strains always seem to inspire a certain sense of gratification.

[i] Khoo HE, Azlan A, Tang ST, Lim SM. Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits. Food & nutrition research. 2017 Jan 1;61(1):1361779. – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613902/

[ii] Köpcke W, Krutmann J. Protection from Sunburn with β‐Carotene—A Meta‐analysis. Photochemistry and photobiology. 2008 Mar;84(2):284-8. – https://pubmed.ncbi.nlm.nih.gov/18086246/

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Ben Taub