Why Does Cannabis Turn Purple? Purple Weed Explained
Quick answer: Cannabis turns purple because of pigments called anthocyanins, the same compounds that make blueberries and red cabbage purple. A plant only turns purple if its genetics carry the genes for these pigments, and the colour is usually brought out by cooler temperatures (especially cool nights late in flower). Importantly, purple colour is cosmetic: it does not mean the weed is stronger, more potent or better, that comes from cannabinoids and terpenes, not colour. Colour shifts tie back to light and temperature, the same forces behind irradiance and illuminance and light-signalled flowering.
Purple cannabis is striking, and it is natural to wonder what makes a weed plant turn purple, and whether that colour means anything. The short answer is that purple comes from anthocyanins, natural pigments the plant can produce if its genetics allow, usually revealed by cooler temperatures as the plant ripens. It is the same kind of pigment that colours blueberries, aubergines and red cabbage.
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Auto Purple CBD
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CBD | 17% – 19% (Medium) |
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Type | CBD Autoflowering |
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Yield | Low |
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Phenotype | 70% Indica / 30% Sativa |
Amnesia Purple
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THC | 18% - 21% (Medium) |
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Type | Feminized |
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Yield | High |
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This guide focuses on the science and the growing side: why cannabis turns purple, the role of genetics versus temperature, how to encourage purple colour safely, and the honest truth about whether purple weed is any ‘better’. If instead you are looking for a list of the best purple strains to buy, we link to our dedicated guide for that, this article is about understanding and growing the colour itself.
| Why cannabis turns purple | Detail |
|---|---|
| Anthocyanins | Purple pigments in the plant, the same family that colours blueberries and red cabbage |
| Genetics | The strain must carry the genes to produce anthocyanins; many never turn purple |
| Cool temperatures | Cooler nights late in flower can bring out purple in strains that have the genes |
| Not a potency sign | Purple colour does not mean stronger or better weed; it is cosmetic |
What Makes Cannabis Turn Purple?
The purple colour comes from anthocyanins, a group of natural pigments in the plant that appear purple, blue or red depending on conditions. Two things must come together for a plant to turn purple: the right genetics and the right environment. The strain must carry the genes to produce anthocyanins in meaningful amounts, many strains simply never turn purple no matter how you grow them, because they lack the genetic potential.
When the genetics are there, the pigments are often masked by green chlorophyll during most of the grow, and become visible as chlorophyll breaks down late in flowering, especially when triggered by cooler temperatures. This is why purple strains often ‘show their colours’ in the final weeks, particularly with cool nights. So purple is a combination of nature (genetics) and nurture (environment), not something you can force on a green-only strain.
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How to Grow Purple Cannabis (Safely)
To grow purple cannabis, start with the genetics: choose a strain known to express purple (many ‘purple’-named strains do). Without the genes, no growing trick will work, and you should ignore dangerous myths like starving plants of oxygen or shocking them with ice, which stress or harm the plant without reliably producing colour. The real, safe lever is temperature: in the final weeks of flowering, slightly cooler night-time temperatures help anthocyanins show through as chlorophyll fades.
So the recipe is simple and safe: purple genetics plus a modest drop in night temperatures late in flower, while keeping the plant healthy. Do not harm the plant chasing colour, healthy buds matter far more than their shade. If you want strains bred to turn purple, see our guide to purple marijuana strains, and for a harvest-time curiosity, our post on ice-water purple buds.
Is Purple Weed Better or Stronger?
Here is the honest truth: purple weed is not inherently stronger, more potent or better than green weed. The colour comes from anthocyanins, which are cosmetic pigments, not a measure of THC, and potency and effect depend on cannabinoids and terpenes, which have nothing to do with the purple hue. A gorgeous purple bud can be weaker than an ordinary green one, and vice versa.
Purple weed can sometimes cost more simply because it looks striking and is in demand, bag appeal, not because it is pharmacologically superior. Some people also associate certain purple strains with relaxing effects, but that is down to those strains’ genetics, not the colour. So enjoy purple cannabis for its beauty, but judge quality by the actual profile (cannabinoids, terpenes, grow quality), not the colour. For strains chosen on effect, browse our feminized seeds.
Does Purple Weed Taste or Smell Different?
A common assumption is that purple weed tastes sweeter or like berries, but the colour and the flavour are produced by different things. The purple comes from anthocyanin pigments, which are largely flavourless, while taste and aroma come from terpenes. Many purple strains do happen to have sweet, fruity or grape-like terpene profiles, which is probably where the association comes from, but it is the genetics behind those terpenes, not the purple colour itself, doing the work.
So a purple bud is not automatically sweeter or tastier than a green one; a green strain can be just as fruity, and a purple one can be earthy or gassy. Enjoy the striking colour for what it is, visual appeal, and judge flavour by the strain’s terpene profile. As with potency, colour and quality are simply not the same thing.
FAQs
Why does cannabis turn purple?
Because of anthocyanins, natural purple pigments the plant produces if its genetics allow. The colour is usually revealed by cooler temperatures (especially cool nights late in flower) as green chlorophyll fades. Without the right genes, a strain will not turn purple. The colour is cosmetic and does not indicate potency.
How do you make a weed plant turn purple?
Start with a strain that has the genetics to produce anthocyanins, then encourage it with slightly cooler night temperatures in the final weeks of flowering as chlorophyll fades. Avoid dangerous myths like oxygen-starving or icing plants, which harm them without reliably adding colour. Healthy buds matter more than shade; no trick turns a green-only strain purple.
Is purple weed stronger or better?
No. Purple colour comes from cosmetic anthocyanin pigments and does not indicate THC, potency or quality, those depend on cannabinoids and terpenes, not colour. A purple bud can be weaker than a green one. Purple weed sometimes costs more for its looks (‘bag appeal’), not because it is pharmacologically superior. Judge quality by the profile, not the hue.
Does purple weed taste like berries?
Not because of the colour. Purple comes from largely flavourless anthocyanin pigments, while taste comes from terpenes. Many purple strains happen to have sweet, fruity or grape-like terpene profiles, which drives the association, but the colour itself adds no flavour. A green strain can be just as fruity. Judge flavour by the terpene profile, not the hue.
