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purple stem on weed plant

Stems of cannabis plants turning purple, how do I fix this?

Question: Help! My cannabis plants are young (growing in soil indoors with sunlight and my leaves are medium sized) yet my main stems are turning purple from the top downwards. Have you seen this before?

Answer: When a cannabis plant or seedling has a purple stem without any other signs of problems, it is often the result of genetics. However, sometimes you’ll see red stems (pictured below) which are often caused by light exposure (kind of like a “tan”), nutrient deficiencies, various types of stress, poor environment, or pH problems.

Wait a week or two before making any alterations if your plant otherwise appears healthy and is growing fast.

If there are no other symptoms and the rest of the plant is growing fast and healthy, red stems usually aren’t a big deal. As long as you’re continuing to take good care of your plant and responding quickly to any other problems, you should be okay.

These red stems were caused by transplant shock and overall stress, but the clone just needed some TLC and time to grow out of it.

Truly purple stems are often caused by genetics

If you believe there is a nutrient problem with your cannabis plant, for example, if your plant is also growing slowly or the leaves are discolored, then the plant may be suffering from…

  • Incorrect pH – The pH being too high or too low at the roots is the most common reason to see a nutrient deficiency)
  • Magnesium deficiency can cause purple stems. A good cannabis-friendly nutrient system has a significant amount of magnesium, but if you’re using very soft water, or RO water, you may need to add a Cal-Mag to your nutrient regimen.
  • Temperature – Heat or especially cold can trigger red stems in some places. Big temperature fluctuations can also do it even if the temperature is in a good range.
  • Humidity – Very high or low humidity can stress plants (especially young seedlings)
  • Other types of stress such as light burn, transplant shock, or overwatering can trigger red stems
  • Sometimes you’ll never know why and plants just grow out of it 🙂

[Answer inside!] What do I do if the stems of my cannabis plant are turning purple?

Purple Stems

Zakattack
ShroomKing
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Bush Doctor
Nicolo
Zakattack
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gingerscotty
Bulldog420
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Bulldog420
Premium Member

Check this out @Slownickel . Thoughts? It would explain a few of my questions.

Bulldog420
Premium Member

Also, come season time. How can we test this out? Take a tissue sample of the leaf with a purple stem, then a tissue sample from the main shoot with no purple? Very interesting. Got me thinking.

@GT21 you thinking genetics then?

mendopeman
Seamaiden
Living dead girl

I don’t know how many folks here have had the opportunity to grow the same strains both indoors and out, I have had that opportunity. And, based on being able to do that, it is my opinion that this kind of petiole reddening is 100% related to phosphorous utilization, and, again based on my own experience, it’s incredibly common in indoor cultivation, and can be rather difficult to diminish or eliminate.

Again, based on my experience and opportunities, I’ve also been able to observe that when it’s related to genetics, the entire stalk and all stems have purpling, often in a striped form. Not just the petioles.

OR poor P utilization. In other words, it may be present, but not available.

Here, non-cannabis sourced information. Scroll to the phosphorous portion.

But, like others are saying, your girls look pretty darn healthy. I’m not sure I’d worry about it too hard. I would continue to observe, and I might range pH to see how the plants respond.

I have more if you like. 🙂

I like soup

Also, come season time. How can we test this out? Take a tissue sample of the leaf with a purple stem, then a tissue sample from the main shoot with no purple? Very interesting. Got me thinking.

@GT21 you thinking genetics then?

Zakattack

I don’t know how many folks here have had the opportunity to grow the same strains both indoors and out, I have had that opportunity. And, based on being able to do that, it is my opinion that this kind of petiole reddening is 100% related to phosphorous utilization, and, again based on my own experience, it’s incredibly common in indoor cultivation, and can be rather difficult to diminish or eliminate.

Again, based on my experience and opportunities, I’ve also been able to observe that when it’s related to genetics, the entire stalk and all stems have purpling, often in a striped form. Not just the petioles.

OR poor P utilization. In other words, it may be present, but not available.

Here, non-cannabis sourced information. Scroll to the phosphorous portion.

But, like others are saying, your girls look pretty darn healthy. I’m not sure I’d worry about it too hard. I would continue to observe, and I might range pH to see how the plants respond.

I have more if you like. 🙂

Send it all my way! I’m all ears for learning as much as possible.. If it does turn out to be poor P utilisation, how would you suggest I correct that? I have attached a picture of my reasoning for making my water at pH 5.8. Would you maybe suggest I go a Lil higher on the ph an see if that makes a difference?

Hi I was hoping someone could help. I've got some purple stems that seem to be getting darker.. I have been spraying them 3-4 times a day with a solution of… ]]>