How to Grow Purple Cannabis
Every grower has fantasised about harvesting big, purple buds at home. But what exactly can you do to manipulate the colour of your weed?
Purple cannabis certainly does exist, but there’s a right way to turn your pot purple, and a wrong way.
HOW TO GROW PURPLE CANNABIS
Purple weed is real eye candy. And while there are many rumours circulating the internet about how to grow purple cannabis at home, there are really only two variables that you can play with to manipulate the colour of your weed. Keep reading to find out what they are.
WHAT CAUSES CANNABIS TO TURN PURPLE?
All plants have naturally occurring pigments. The most dominant pigment in most plants (including cannabis) is chlorophyll, which, apart from helping plants photosynthesise, also gives them their green colour.
However, plants also have many other active pigments, including carotenoids and anthocyanins. In the absence of chlorophyll, plants may use pigments like anthocyanins to absorb sunlight and photosynthesise. Unlike chlorophyll, anthocyanins naturally absorb all wavelengths from the sun except those in the indigo spectrum, which is what gives plants their purple colour.
Hence, purple cannabis plants (or any purple plant for that matter) get their colour because the dominant pigment in their leaves and flowers are anthocyanins, rather than chlorophyll.
WHAT PARTS OF CANNABIS CAN TURN PURPLE?
There are four main parts of your cannabis plant that can turn purple:
• Pistils: Pistils are the fine hairs that pop out of your buds, letting you know they’re female. Pistils generally start off a creamy white colour and turn orange/red/brown as plants mature. However, it is possible for your plant’s pistils to turn pink or purple, and this colour will remain after you harvest, dry, and cure your buds.
• Calyxes: Calyxes are the small pods that make up your buds. Cannabis flowers are actually made up of hundreds of these small calyxes stacked on top of one another. As the flowers mature, the calyxes open and reveal their pistils, which are designed to catch pollen from male cannabis plants.
• Leaves: The fan and sugar leaves of your cannabis plant can also turn purple. However, they usually won’t have a large effect on the final colour of your buds, as you’ll likely trim away most of the leaves during your post-harvest work.
• Trichomes: Trichomes are the tiny crystals that cover your buds. While they usually start off clear and become opaque and then amber later on, it is possible for them to turn purple, too.
THE WRONG WAYS TO TURN YOUR POT PURPLE
Many people mistakenly believe that the best way to turn cannabis purple is to deprive their plants of oxygen. However, depriving your plants of oxygen, carbon dioxide, or any other gas will not improve your chances of harvesting purple buds. Feeding your plants more nitrogen also won’t change the colour of your plants, at least not unless you overdo it and end up burning them to a crispy shade of brown.
Some growers also use food colouring to dye their plants. And while it might work, we definitely do not recommend trying it. Finally, changing your plant’s light cycle, watering schedule, or grow medium also won’t increase its chances of turning purple, nor will yelling, screaming, or singing to your plants.
THE RIGHT WAYS TO TURN YOUR PLANTS PURPLE
Now that you know how NOT to go about growing purple weed, here are a few pointers to help you maximise your chances of harvesting some eye-catching purple buds this season:
1: START WITH THE RIGHT GENETICS
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. Remember that your buds are going to lose some colour after trimming, so opt for strains with the most vibrant purple pigmentation you can find.
Keep reading through to the end of this article for some top recommendations on purple strains to grow at home.
2: ADJUST YOUR TEMPERATURES
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.
OTHER WAYS TO GROW PURPLE WEED
There are some other ways to manipulate the colour of your plants. Most of these techniques, however, involve depriving your plants of certain nutrients, which, of course, we do not recommend doing. Even if you are able to achieve some purple colouration using these alternative methods, it will likely be to the detriment of quality, flavour, and potency.
GENETICS: THE #1 REASON WEED TURNS PURPLE
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.
At Royal Queen Seeds, our expert breeders have bred some killer purple strains. Make sure to check them out and add a splash of colour to your next harvest:
Purple Queen is an almost pure indica variety bred from Hindu Kush and Purple Afghani genetics. She flowers over 9–11 weeks and produces big, purple buds with a uniquely pungent aroma that combines hints of both pine and fuel. Purple Queen also boasts a THC concentration of up to 22% and produces a nice, relaxing body stone that’s perfect for whenever you need to unwind and relax.
Perhaps you've seen brilliant purple bud. Perhaps you've even accidentally grown it. Now, you'd like to do it on purpose. Here is the ultimate guide to making your bud glow with that unique purple hue.
Should You Worry About Purple Or Red Cannabis Stems?
Finding red or purple stems on your cannabis plants might freak you out, but it’s not necessarily a cause for concern. Keep reading for an overview of the potential causes of red or purple cannabis stems.
Red or purple stems in cannabis can be a sign of stress, nutrient deficiency, pathogens, or simply genetics. Keep reading to learn when to be concerned about red stems, and when not to.
RED OR PURPLE STEMS CAUSED BY GENETICS OR LIGHT
You might be alarmed the first time you spot red or purple stems on your cannabis plants. But you don’t always need to be. There are countless strains of cannabis on the planet, and some of them are capable of developing incredible pigmentation.
Purple strains with very dark foliage, for example, often develop purple stems too, especially if you grow them in slightly cooler temperatures. As long as your plants look otherwise healthy, there’s usually no reason to worry.
Other than genetics, another major cause behind discoloured stems is strong light exposure. If you use training methods like LST or defoliation, you may notice the exposed stems of your plants turning red, pink, or purple over time. This is completely normal and shouldn’t be cause for concern as long as your lights are sufficiently distanced and your plants look otherwise healthy.
RED OR PURPLE STEMS CAUSED BY STRESS, NUTRIENT DEFICIENCY, OR ENVIRONMENT
Unfortunately, red or purple stems in cannabis can also be a sign of stress. When this is the case, your plants will usually experience some other symptoms that can help you narrow down the root cause of the problem.
Some fungi, such as Fusarium or Botrytis, can affect the colour of your plants’ stems and foliage. Fusarium affects seedlings, attacking their stems and eventually causing them to topple over or “damp off”. It can sometimes make stems appear dark brown, red, or slightly purple. Botrytis, on the other hand, affects larger plants and forms a characteristic brown line along the affected stems and branches, robbing them of nutrients and causing them to die.
Both Fusarium and Botrytis can spread from one plant to another and should be taken care of as soon as possible. Check out our previous posts on Fusarium and cannabis moulds for more information on how to deal with these deadly pathogens.
Nutrient deficiencies cause a wide range of symptoms, including yellowing/drying new and old foliage, and discoloured stems and leaves. In particular, some of the early signs of a phosphorous deficiency include red and purple stems, followed by brown, dried out leaves. Magnesium deficiencies, on the other hand, tend to cause petioles (the stalks attaching a leaf to a stem) to turn red.
If you’re worried your plants might be dealing with a nutrient deficiency, check out this post for pictures, descriptions, and easy-to-follow steps on how to identify and cure every cannabis nutrient deficiency.
Remember, nutrient deficiencies don’t just cause discoloured stems; they also cause signs of stunted growth, damaged foliage, and more. Make sure to identify the type of deficiency affecting your plants using our guide and rectify it as soon as possible.
A NOTE ON pH
Getting the pH of your soil and nutrient solution right is essential for healthy plants. Unfortunately, it’s also something a lot of growers struggle with.
Cannabis likes slightly acidic soil (we recommend keeping it at 6.5 for best results). If your soil is either too acidic or too alkaline, your plants can lose healthy foliage and develop nutrient deficiencies as they struggle to uptake nutrients from your fertilisers. If your plants have red or purple stems and other signs of a nutrient issue, make sure to check your pH levels.
For a clear picture of the pH of your soil, we recommend investing in pH and conductivity testers. These tools provide accurate readings of your soil pH as well as the electrical conductivity of your nutrients, meaning you’ll be able to see just how well your plants are absorbing their fertiliser.
Abrupt changes in temperature can often cause changes in pigmentation in cannabis plants. Cool nighttime temperatures in particular can lead your plants to develop dark red or purple foliage and stems. This is even more common in purple strains; in fact, growers often expose purple strains to cooler nighttime temperatures on purpose to really highlight the purple gene.
If your plants turn red or purple after a particularly cold night, pay close attention to them over the following days. If they continue to grow normally, then there’s nothing to worry about. If, however, you notice slowed growth or other signs of stress, bring up the temperature in your grow room (or consider moving your plants indoors if you’re outdoors).
Cannabis plants react to stress in myriad ways. Sometimes, discoloured stems can be a sign of transplant shock, heat stress, overwatering, or even a bug infestation. That’s why, if you spot purple or red stems, it’s important you pay close attention to identify the root cause of the discolouration.
Below, you’ll find a checklist of potential stressors that might be causing your plants to develop red or purple stems:
• Root shock: Transplanting comes as a big shock to the root system. If your plants develop red or purple stems after being transplanted, a good dose of TLC should help them recover quickly.
• Pests or plagues: Some cannabis strains are more prone to pests and plagues than others. If your plants have discoloured stems and also suffer from damaged foliage, stunted growth, and signs of mildew, gnats, or spiders, you’ll need to act quickly. Check out this post on common cannabis ailments for more info on how to spot and treat common cannabis pests.
• Temperature or humidity issues: If the temperature or humidity levels in your grow room feel off, that may be part of your problem. Adjust temperature/humidity if you suspect they could be stressing your plant.
• Light/heat stress: While cannabis loves warm weather and plenty of sun, too much heat or light can damage it. If your cannabis plants develop burnt or yellow foliage, bleaching, or curled leaves a few days after you first notice their discoloured stems, they might be dealing with light or heat stress. Be quick to address these issues, as they can have a devastating effect on your plants and greatly reduce the size and quality of your yield.
GETTING TO THE BOTTOM OF RED OR PURPLE CANNABIS STEMS
As we saw earlier, red or purple cannabis stems aren’t necessarily a cause for concern. If your plants suddenly develop discoloured stems, remember to monitor them closely and look out for other symptoms that the discolouration isn’t caused by genetics or light exposure. Also, visit the growing section of our blog for more detailed articles on how to grow cannabis, deal with nutrient deficiencies, pests, heat stress, and more.
Seeing red or purple stems on your cannabis plants? Don't freak. Click here for a detailed overview of the causes behind purple or red cannabis stems.