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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.

PATHOGENS

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 DEFICIENCY

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.

TEMPERATURE FLUCTUATIONS

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).

STRESS

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.

Why Does Weed Turn Purple? Truths and Myths about Purple Cannabis

Thursday April 5, 2018

I n these modern times of cannabis consumption bad information still runs rampant, and few things in the world of weed have as large a mythic standing as purple bud. This seemingly simple topic can actually be a bit convoluted, starting with, what is purple bud? The short answer is cannabis flowers that exhibit a darker, purple-tinged hue. However, it is not always the shade most people think of as “purple.”

Purple cannabis can be a tricky concept. Just stop for a moment and contemplate the timeless line, “roses are red, violets are blue.” A modern sensibility would correct that the color of violets is none other than violet. Similarly, purple weed is not always “purple.” It can have a wide range of presentation, from dark green to even black.

Why is Some Cannabis Purple?

Consider that what we call a blueberry is also usually quite purple. This is because the very thing that makes blueberries “blue” is the same as what makes purple nugs “purple,” anthocyanins. Anthocyanins are water-soluble pigments present in many plants. Despite the “cyan” in “Anthocyanins” referring to their blue nature, these molecules occur in a range of colors from red to purple to dark blue, or black, depending on pH level.

Anthocyanins are part of a larger class of substances known as flavonoids, which aside from how the name sounds, have very little to do with flavor (and are astringent to the taste). In fact, the “flav” in flavonoids comes the Greek word for yellow, flavus.

This can be a bit linguistically confusing; a blue-named class of molecules that presents as red or purple is a subset of a class of yellow-named molecules. It begins to make sense when we consider that a complex interaction of anthocyanins and other flavonoids is what causes leaves to change their color among such a brilliant spectrum in the fall.

When cannabis presents as purple, we are seeing a similar phenomenon as fall leaves, allowing purple bud to have a wide spectrum as well. Like other plants for cannabis, colors, and changes in color, have purpose. The stressed plant is changing pigment in order to achieve a goal before wilting in the cold, such as conserving energy or increasing chances for pollination.

For cannabis strains, the ability to present darker pigments, and to what degree, is wholly dependent on the plant’s genetics.

Without a predisposition to purpling, a given strain cannot be induced to turn purple. Certain strains will have more naturally occurring anthocyanins than others, and when switching to the “winter” cycle of flowering, will start to express those purple pigments innately according to their genetic predisposition interacting with the unique chemical and environmental factors in which the plant is grown.

Is Purple Marijuana Better?

Visual appeal aside, is there reason to believe that these royal-toned flowers are better than the green hues more common to the plant? The science leans towards no.

According to the European Food Safety Authority, there is no substantive evidence anthocyanins have any effect on human biology or diseases – though they contain a higher concentration of anti-oxidants, which would theoretically only be beneficial if one were eating buds. There is some minor proven correlation to anthocyanins as an anti-inflammatory, but again, would probably be more active if ingested. Seeking a strain with higher CBD content would be a better source for anti-inflammatory effects than purple hue.

In general, purple bud has a tendency for lower THC content than its greener counterparts. That’s not to say high-THC purple is not possible, we’re sure we’ve all seen or smoked an exception to the rule. That is because most purple bud that we see today is not a result of stressing the plant, but genetics.

To better understand this connection, I spoke with veteran grower and concentrate connoisseur Matt Gosling about the popularity of purple cannabis. While purple bud can be fantastic, he explained, it’s usually due to good breeding and genetics, and not much else.

“Purples are memorable. If you have a good high with purple bud, it’s going to stand out. Then if you’re a grower and you have the ability to then reinforce those genetics you’re going to, and it propagates itself from there.”

Anything beyond breeding could detriment the plant. “Any energy the plant spends pushing out that purple pigment is going to be drawn from somewhere else and is going to hurt overall. It’s just not worth risking the quality for a chance a slightly better bag appeal.”

Myths about Purple Weed

Some people believe that there are growers out there who bring out purple hues by manipulating the plant, however, the prevalence of such practices seems to largely be a myth. I rattled off a list of alleged techniques for inducing purple bud to Matt, such as affecting nutrient levels or flash freezing, and he quickly declared them bunk.

That’s not to say attempts at purpling don’t occur at all, “I’ve seen some people use ice water to do their flush,” he told me, “some other tweaking with light timing, but I don’t recommend any of it.”

In speaking with growers, budtenders, flower reviewers and other cannabis journalists, the consensus among the industry is to treat each harvest as unique–smoke what appeals to you. If the effects of purple strain are appealing, go for it.

Furthermore, no one is wrong to feel that the visual appeal of a flower can enhance the smoking experience. However, ultimately, the mere presence of the pigment is unrelated to the resulting effects. If the flower is good, by all means smoke it, in any spectrum of the rainbow.

What are your thoughts on purple weed? Do you find it to be better than green cannabis?

Matt Mongelia holds an MFA in writing from The School of the Art Institute of Chicago. He has worked in the cannabis industry in various roles for 4 years, from dispensaries, production and retail to events, content and marketing. He is a writer for the comic Dark Beach, and has previously covered music and cultural content for SOL REPUBLIC.

Everyone cannabis enthusiast has a place in their heart for purple weed. Learn about why cannabis turns purple and some of the truths and myths behind it.