A Guide to Growing Purple Cannabis

There are many rumours on the internet about how to grow purple cannabis at home. The growing of purple cannabis requires a well thought of plan specifically aimed at achieving not just the right color of weed but also the standard quality and quantity.

What makes the cannabis plant purple?


When it comes to purple cannabis, it is important to have a well-defined understanding of the truth.  What makes the plant purple? Before we get into what exactly makes weed purple, it’s important to know that the colour of cannabis that people associate with purple can range anywhere from dark green to black. This is because of “Anthocyanin’s”. Anthocyanins are what make blueberry’s blue, and they are what make raspberry’s red. And consequently, anthocyanin’s are what make weed purple.

The colour is dependent on pH levels. In higher pH levels they appear redder, in neutral conditions ( around 7 on the pH scale) it’s purple, and in lower pH levels blue. Cannabis contains anthocyanin’s in all parts of the plant: the stems, roots, leaves, and flowers. A cannabis plant will only start to turn purple in the last few weeks of flowering.

In short, this just means that the colour of cannabis is completely dependent on how acidic that specific plant or strain is.

However, due to the abundance of false information littered all over the internet, a lot of new and potential growers find it difficult to know what to believe.  Several outlets lead growers astray with their unsubstantiated methods of growing purple cannabis, methods that only end up costing growers their valuable time and money. 

Myths about purple weed abound. Most of those myths revolve around how the famous purple hue is achieved when growing marijuana. The most common myths include:

  • Oxygen deprivation – Restricting oxygen will only stunt the plant’s growth, not make it change color.
  • Carbon dioxide deprivation – Carbon dioxide deprivation of marijuana is only a recipe for unhealthy weed, not for turning it purple.
  • Nitrogen overload – Far from turning the plant purple, too much nitrogen will turn a marijuana plant brown.
  • Altering the light cycle – Plants need a certain amount of light each day to stay healthy. If you mess with that process, you’re just going to get unhealthy plants.
  • Changing the growing medium – Plants use the nutrients in the soil to grow but altering the composition or quantity of those nutrients isn’t going to result in purple weed.
  • Varying the amount of water – Grown in the wild, marijuana contends with varying amounts of water on a daily basis and doesn’t turn purple. Varying the amount of water isn’t going to somehow miraculously result in purple buds.

How To Grow Purple Cannabis


Two important factors determine whether weed can, and will, turn purple during its growing cycle: genetics and temperature. Here’s how they work.

Get The Right Seeds

Genetics are going to have the biggest impact on the final colour of your plants. So, if you’re set on growing purple weed, shop around for purple strains, as they’ll have been specifically bred for their unique colour.

So the first step in growing purple weed is to plant seeds that already have a predisposition toward purple (i.e., contain anthocyanin).

Mimic Fall Temperatures

Plants change colors in the fall when temperatures begin to drop from their summer highs. So your best bet for producing purple weed is to mimic these fall temperatures and give the anthocyanin time to work its magic.

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While you might be eager to watch your plants turn purple, this will usually only happen once they’ve finished vegetative growth and start flowering. Once your plants have entered their flowering stage, try dropping your nighttime temperatures. Colder temperatures cause chlorophyll to break down and can encourage your plants to produce more anthocyanins. Ideally, you’ll want there to be a difference of 10–15°C between your daytime and nighttime temperatures.

Tips On Growing Purple Cannabis Strains

  1. In case the plants are growing too slowly, it is recommended to test the soil for suitability and make sure you are using the right fertilizers. Many growers can get demotivated and lose hope when the only problem is not making sure that the soil quality is up to the mark and choosing the wrong fertilizers.
  2. You can grow the plant indoors as well as outdoors but it is always best to keep it indoors since you can control the environment easily and keep it safe from external factors such as animals, kids or jealous neighbors.
  3. Purple marijuana plant can grow as high as two to three feet so take that into account while setting up your cultivation facility.
  4. The best time to enjoy your purple cannabis is when it is almost nearing the harvest stage so be sure to plan your activities accordingly to get the most out of it, be it sharing the good stuff with your friends or selling it off to your customers.

Popular Purple Cannabis Strains

Purple Kush

Purple Kush is a pure indica that sets itself apart from other indica hybrids with its eye-catching colors and pleasant taste. The tendency towards purple, selectively bred from the Purple Afghani parent strain, comes about when the plant’s anthocyanins — pigments similar to chlorophyll — are activated in cold growing conditions.

Purple Haze

Purple Haze buds typically acquire vibrant hues of lavender that further justify the naming of this strain.

Lavender Kush

Lavender Kush has dense buds that give off a floral and spicy aroma. It has a dark purple coloration at the ends of its leaves.


Remember, the two main factors affecting the colour of your cannabis plants are genetics and temperature. If you’re really set on growing purple weed, make sure to invest in the right genetics from the get-go.

[Updated, originally published 2.11. 2019]

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