What Makes Weed Purple?

Purple cannabis has always been of great fascination to both growers and consumers, standing out with its striking hues and deep, vibrant shades. But, what exactly causes this colour change? Is it purely genetic, or do environmental factors play a role?

Well, in this article, we're going to talk about just that. We'll examine what makes weed purple and highlight some of the best purple strains that develop rich colours when exposed to cooler temperatures.

The Science Behind Purple Cannabis

The purple colour in cannabis is primarily caused by anthocyanins, a group of water-soluble pigments found in many plants, including berries, grapes and red cabbage. These pigments are actually responsible for a range of colours, including red, blue and purple, depending on their pH and environmental conditions.

Unlike chlorophyll, which gives cannabis its typical green colour, anthocyanins become more prominent when chlorophyll breaks down. This process is most noticeable in the later stages of flowering, especially when plants are exposed to cooler temperatures.

Factors That Influence Purple Colouration

While anthocyanins provide the potential for cannabis to turn purple, several key factors determine whether a plant will actually develop these colours.

Genetics: The Foundation of Purple Strains

Not all cannabis plants have the ability to turn purple. The presence of high anthocyanin levels in a strain's genetics plays a major role. Some strains are naturally predisposed to developing purple hues, while others will remain green regardless of environmental conditions.

Temperature: The Colour Trigger

One of the biggest influences on purple cannabis is temperature. When nighttime temperatures drop significantly during the flowering stage, chlorophyll production slows down, allowing anthocyanins to take over. This process mimics the way leaves change colour in autumn.

For the best purple colouration, aim for a temperature drop of 8-10°C between day and night during flowering. But, it's important to avoid extreme cold, because frost or excessive cold stress can damage plant health.

Light Exposure: Enhancing Anthocyanin Production

Purple hues can also be intensified by adjusting light exposure. Higher levels of UV light have been linked to increased anthocyanin production. Some growers use LEDs with UV spectrums to encourage deeper colouration, while outdoor growers may notice more intense purpling in sunny environments.

pH Levels: Acidic or Alkaline Influence

The pH of a plant's growing medium can affect anthocyanin expression. While cannabis generally prefers a slightly acidic pH (between 6.0 and 6.8 in soil, or 5.5–6.5 in hydroponics), some growers experiment with pH variations to encourage more colouration. However, drastic pH changes can lead to nutrient deficiencies, so caution is advised.

Nutrient Availability: Balancing Phosphorus and Nitrogen

Nutrient levels also impact colour expression. Some growers find that reducing nitrogen in the later flowering stages while maintaining phosphorus and potassium levels encourages purpling. However, nutrient deprivation should be done carefully to avoid harming the plant.

Popular Purple Cannabis Strains

Certain strains are genetically predisposed to turn purple, especially when exposed to colder temperatures in the flowering stage. Below are some of the best purple varieties available at Oaseeds that develop stunning shades under the right conditions.

1. Purple Punch

Purple Punch is a strong indica-dominant hybrid known for its deep purple hues and sweet, fruity aroma. This strain thrives in cooler flowering temperatures, with rich anthocyanin levels leading to its signature vibrant colours.

2. Granddaddy Purple

One of the most famous purple strains, Granddaddy Purple (GDP) is a cross between Purple Urkle and Big Bud. It produces deep purple buds with bright orange hairs, offering a classic grape and berry flavour profile.

3. Blackberry Kush

Blackberry Kush is a potent indica variety that frequently develops dark purple and blue shades. It flourishes in colder environments, and its sweet berry aroma makes it a favourite among purple strain enthusiasts.

4. Purple Haze

A sativa-leaning classic, Purple Haze is known for its purple-tinged buds and uplifting effects. This strain responds well to temperature fluctuations, developing rich violet hues in colder grow spaces.

5. Black Domina

Black Domina is an indica strain that features dark green and deep purple tones when exposed to lower temperatures. Its fast-flowering properties and intense sedative effects make it a popular choice for night-time use.

6. Dark Devil Auto

For autoflowering growers, Dark Devil Auto is an excellent choice. This strain develops beautiful shades of purple and red throughout its lifecycle, making it visually striking as well as potent.

Growing Tips for Enhancing Purple Colouration

To bring out the best purple shades in your cannabis plants, follow these tried-and-tested growing tips:

• Select a strain with high anthocyanin levels: Genetics is the primary factor in achieving a vibrant purple colour.
• Drop nighttime temperatures: A decrease of 8–10°C between day and night can encourage anthocyanin expression.
• Use LED lights with a UV spectrum: This can help deepen the intensity of purple hues in indoor grows.
• Maintain proper nutrient levels: Reducing nitrogen in late flowering while maintaining phosphorus and potassium can support colour development.
• Harvest at the right time: Some strains develop darker purple hues in the final weeks of flowering, so be patient for the most striking results.

What Role Do Terpenes Play in Purple Cannabis?

While anthocyanins are responsible for the colour of purple cannabis, terpenes play a key role in the flavour and aroma. Plenty of purple strains are known for their sweet, berry-like or fruity scents that come from specific terpenes such as myrcene, limonene and pinene. These compounds not only influence taste but may also contribute to the entourage effect, enhancing the overall experience of cannabis consumption.

For example, Granddaddy Purple and Purple Punch both contain high levels of myrcene, giving them a grape-like aroma and relaxing effects. Meanwhile, strains like Purple Haze have a citrusy kick due to their limonene content.

While the deep purple hues are visually striking, they don't directly impact potency or effects - it's the terpene and cannabinoid profile that determine a strain's impact.

When selecting purple strains, it's worth considering their terpene profile to find one that suits your preferred taste and experience.

Does Purple Weed Indicate High Quality?

One common misconception is that purple cannabis is always stronger or of higher quality than green varieties. In reality, colour does not determine potency, as THC and CBD levels depend on genetics, cultivation techniques and curing methods. A visually stunning strain with deep purple hues may still have moderate THC levels, while a green strain could be significantly more potent.

However, many consumers associate purple cannabis with premium quality because strains that develop these hues often have well-balanced terpene profiles, producing flavourful and aromatic buds. Also, growers who take the time to cultivate purple strains under the right conditions tend to focus on careful plant management, resulting in high-quality harvests.

Ultimately, when choosing a cannabis strain, effects, aroma and potency matter more than colour. While purple strains are undeniably beautiful, their true appeal lies in their unique genetics and sensory experience rather than just their appearance.

FAQ: What Makes Weed Purple?

1. Can all cannabis strains turn purple?

No, only strains with high anthocyanin content can develop purple hues. Some strains remain green regardless of environmental conditions.

2. Will growing in the cold always make cannabis purple?

Not necessarily. Cold temperatures can enhance purple colouration in certain strains, but without the right genetics, cannabis is probably going to stay green.

3. Does purple cannabis have higher potency?

The colour of cannabis doesn't directly affect THC or CBD levels. But, having said that, some purple strains are naturally potent due to their genetics.

4. Are purple cannabis strains harder to grow?

Not always. Some purple strains are just as easy to cultivate as green strains, provided they receive the right conditions for colour enhancement.

5. Does purple cannabis taste different?

Many purple strains have sweet, fruity, or berry-like flavours, but this is due to their terpene profile rather than colouration.