What's the Purple in Cannabis?

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What's the Purple in Cannabis?

Purple cannabis is a feast for the eyes, but what causes it? How do you turn your cannabis purple? And does it actually have any practical use?

Although not as common as their greener cousins, purple varieties of cannabis have been around for ages. The legendary Purple Haze strain (which, you guessed it, flowers purple), has even been sung about by Jimmie Hendrix. It is no wonder really, with their vibrant and eye catching colours, who wouldn’t want some? But what causes it?


The reason your bud can sometimes be purple (depending on strain), is thanks to anthocyanin. It is a group of around 400 water-soluble pigments that can appear red, blue or purple depending on the pH. If pH is near neutral, as it should be, then any cannabis strain with an abundance of this pigment will likely end up with purple bud!

Anthocyanin isn’t actually produced by cannabis until the last few weeks of its life, where it can show up thanks to the reduced amounts of chlorophyll that would otherwise block it from view. When cannabis flowers, it is triggered due to the fact that it is getting less light. This reduction in light results in less chlorophyll being produced. This can even be seen in cannabis plants that don’t produce much anthocyanins – with gold and orange hues often appearing within a plant’s last weeks.


Enough with the science though, how do you actually turn your cannabis purple? Well firstly, you need a strain of cannabis that produces a lot of anthocyanin. Such strains include Blue Mystic, Haze Berry, Northern Lights, Purple Haze, and Blue Cheese, (although there are many more).

In the last two weeks of flowering, change the temperature of your grow room so that it remains constantly below 10 degrees Celsius, but above 4 degrees. For most strains, this cold temperature is also required to really bring out the colour – it is not fully understood why, but there is a clear link. Although most strain can deal with the cold, just make sure not to make the drop in temperature too sudden, or you could cause your plants to go into shock - consider doing it gradually.

Whilst a cold temperature is often required, selective breeding has allowed certain variations of some strains to turn purple even when at normal temperatures. Meaning you still get the awesome colour without putting your plants at risk.

There are reports that depriving your plants of oxygen, carbon dioxide, or even certain nutrients can turn your bud purple, but never do this. It is very unsafe for your plants, and you will be sacrificing their health (and potential quality/yields) for something that is mainly cosmetic. Subjecting your plants to a colder temperature is much safer.


For those of you wondering if anthocyanin actually has any benefits, you will be pleased to know it does. It is a known and powerful antioxidant thought to have analgesic, anti-inflammatory and neuroprotective properties. How effective this is when smoked is unknown, but it certainly can’t hurt!