Start My Diary Login Sign Up
Sign In

Why Do Cannabis Buds Turn Purple?

Created by
JoshuaHolt JoshuaHolt
Added 11 November 2020

Why Does Cannabis Turn Purple?

If you enjoy cannabis on a regular basis, then you've probably come across purple weed before. Purple strains have caught the attention of stoners not only for their beautiful hues, but the apparently rich experience they deliver. This article talks about some of the myths surrounding purple buds and uncovers the real reasons cannabis plants can display such magnificence.

Purple Cannabis Myths

People have come up with all sorts of ideas when it comes to the topic of purple weed. From depriving their plants of nutrients, to inducing extreme cold, growers have tried many techniques to encourage their buds to turn purple.

You may have wondered why cannabis plants show purple colours and heard the following:

Myth 1Stressing a cannabis plant turns it purple
Myth 2Flushing with ice cold water makes weed purple
Myth 3Potency is higher when the buds are purple
Myth 4Purple weed makes you sleepy

In some cases the theories may be true, but there are some facts about the pigments of plants that cannot be ignored.

Why Does Cannabis Turn Purple?

Purple Cannabis Buds

Now we have the myths over and done with, let's take a look the proven reasons for purple pigments in plants. The reaction is similar to the way leaves in nature change during autumn. Plants do this mainly because of how light and temperature change throughout the year.

Less photosynthesis during winter means less chlorophyll is produced and eventually the typical green colour fades. This allows other compounds develop, which in turn affects the hue. Depending on the type of plant, a whole range of different pigments can emerge.


Chlorophyll is the green pigment in cannabis that aids light absorption. How much chlorophyll a cannabis plant can produce is determined by its genetics

Chlorophyll Makes Cannabis Green

Although chlorophyll is not necessarily the reason for purple pigments, it does play a role in how a cannabis plant changes colour. As temperatures drop and the plant matures, photosynthesis slows down and the need for chlorophyll decreases. This is why most cannabis plants that are nearly ready for harvest lose most of their green colour.


Anthocyanins form part of a larger group of flavonoids. Flavonoids are similar to terpenes but they serve different purposes. They can be found in many types of plant, including many fruits and vegetables, and can express a broad spectrum of impressive colours.

Cannabis That Contains Anthocyanin Turns Purple When It Gets Colder

The presence of anthocyanins can be high enough for plants to show deep blues or purples all through maturity, such as with blueberries or eggplant. Studies have shown that anthocyanins have antioxidant and anti-inflammatory properties.

Flavonoids and primarily anthocyanins are responsible for the red, blue or purple colours seen in some plants as they mature. Without them it is quite unlikely the flowers are able to turn purple, even if the environment encourages the plant to do so.

Anthocyanin Present In Many Fruits And Vegetables


We already touched on how genetics can determine whether a cannabis plant can turn purple or not. Some strains naturally have a high level of anthocyanins and therefore display more purply tones when the conditions are in their favour.

Anthocyanins are present in some cannabis strains, but not all of them. Cannabis plants that are genetically determined to develop anthocyanins will turn purple more easily in a strain that does not produce such strong pigmentation.

This may be why Indicas tend to turn purple more frequently than Sativas. Indicas also stem from colder climates, so the level of anthocyanins is normally higher.

Granddaddy Purp, Blackberry and Purple Haze

Strains that have purple tendencies:

  • Granddaddy Purp
  • Blackberry
  • Purple Haze

The Environment

Genetics set the stage for a cannabis plant but its true colours may not show themselves until the conditions signal them to make the change. When the night temperatures drop, the purple hues begin to show themselves when there is a presence of anthocyanins.

Cold Temperatures Encourage Anthocyanin Development

The right environment allows a cannabis plant to live a healthy life. As an annual plant, photoperiod cannabis naturally has one cycle per year. The seasons change and indicate when certain metabolic processes should take place. The time of year will also affect indoor temperatures so you may notice weed turns purple more easily when you are growing through winter.

As it gets colder, the foliage on a cannabis plant darkening could be seen as a type of survival mechanism. Darker pigments absorb and retain heat more easily. It is also thought that a cannabis plant does this partly as a last push to conserve energy and possibly mate before winter. 

Is Purple Cannabis Better?

Purple Cannabis Leaves

Some people claim that purple cannabis is more potent than the green stuff. Amongst all the discussion, there is not any concrete evidence to say that purple weed is any stronger than normal cannabis.

Whether it is better or not depends on why you are consuming a particular type of cannabis. Achieving a specific high requires you to study the cannabinoid content of the strain rather than focus on its colour, which has nothing to do with the 'high'.

Anthocyanins are absorbed mostly through the digestive system so in order to benefit from them you would probably need to eat a fair amount purple bud. Purple cannabis can provide some added medicinal value, however.

Growing Purple Cannabis

There is a lot of information out there about purple weed that may be potentially dangerous for your plants. Encouraging buds to turn purple might be possible, but the techniques to achieve it carry a lot of risks and plants may be seriously affected if they are not performed correctly. Only go ahead if you know the strain you are growing has the capability to turn purple.

Indoor growers have experimented by slowly reducing temperatures during flowering as a way to coax out the purple hues. Mimicking the outdoor conditions can make the plant 'think' winter is coming and can kick start anthocyanin production.

Understand that cold temperatures can invite mold, especially during late flower. This is why the temperatures should be reduced gradually to avoid shocking your plants or keeping them cold for extended periods of time.

Once your cannabis plants get close to harvest (around 5-7 days before), the night temperature can be reduced slightly each day, until it sits around 10 - 12°C. If your plants are purple strains, it is likely they will already be showing purple colours but this process could help to bring them out further. Remember, carefully monitor your plants during this time.

Purple Kush (Crop King Seeds) by iMpulsive_Grow from GrowDiaries.


The best way to get purple weed is simply to grow strains that have these qualities. Trying to make your weed purple won't make it any stronger and you risk messing up your hard work by attempting to apply some of the conflicting techniques growers propose. In the end though, nature will run its course with or without our help. Purple weed just makes it that little bit more special.

If you found this article useful, please feel free to drop a comment down below! We'd love to hear about all the purple weed you've had the pleasure of experiencing.

External References

Early identification of tomato genotypes expressing mutations involved in the synthesis of anthocyanins. Acta Horticulturae. - Santangelo, Enrico & Picarella, Maurizio & Mazzucato, Andrea & Soressi, G.P.. (2012)

Anthocyanin pigments: Structure and biological importance. Journal of Chemical and Pharmaceutical Sciences. - Nassour, Rana & Ayash, Abdulkarim & Al-tameemi, Kanaan. (2020).

Cannabis sativa and Cannabis indica versus “Sativa” and “Indica”. - McPartland, John. (2017).

Anthocyanins: Antioxidant and/or anti-inflammatory activities. Journal of Applied Pharmaceutical Science. - Miguel, Maria. (2011).

This article was updated October 2020.



I love Purple weed, beautiful plant!


"Although chlorophyll is not necessarily the reason for purple pigments"

I'd say chlorophyll has actually nothing to do with purple. Also, the "external references" look like a shallow search on google scholar, those papers are not particularly related to the article whatsoever, apart from the presence of term 'anthocyanins'. I'm sorry to say this post looks pretty useless to me.