purple stems weed

Purple seedling stems!

Well-Known Member

So i see a lot of people have purple stems and wonder how the hell it happens. Well for those who ask the answer is all too often ‘GENETICS’ or temps.

I see it as a sign of overwatering, seedlings need very little water indeed, you really would be suprised. If the roots stay wet for too long then you get purpling of the stem from phosphorous deficiency/lockout.

I grow the same seeds from the same strain and same mother, i use peat cubes but only till the seed germinates at which point the peat cube holds too much water for my liking, its like a sponge not good for drainage. So i prick the seedling out of the peat cube and replant it in my seedling soil that is amended with perlite or vermiculite.

The pics show what a healthy seedling stem should look like, pics one and two notice no purple stem or leaf veins or leaf! This is the only colour you want your seedling stem to be, unless you are growing a purple strain of which very few do or have. It is not genetics 9 out of ten times but simply overwatering.

Myth solved but open to discussion!?

Sorry last pic is my tumbling tom cherry tomato plant.

Well-Known Member
Well-Known Member

Sorry but i beg to differ, purple is only for the purple strains! I know people have purple on the plants but that dosent really have to be there. A little is acceptable but a lot occurs on a sick plant. I am only talking seedlings here as the rest is another thread.

I worked at it and am now not getting any purple, seriously weed growers dont get it like the vegetable sites do. It is linked to phosphorous lockout and sometimes iron def. Phosphorous def in flowering turns stems and petiols and whole leaves if bad PURPLE and the two times a plant needs high phosphorous is seedling and flowering! Figures now dosent it.

The reason why people quote temp as a reason for purpling stems is that cold locks out phosphorous very quickly and if a seedling is cold and need high amounts of phosphorous which is present in soil but locked out easily with low temps then hey presto the same thing happens, purple stem from phosphorous deficiency! Why dose no one know this or say genetics, thats a myth for purple strains.

Seriously look at my seedling, no purple and it had very minimal water since it sprouted and good drainage, perfection is almost there for me and seedlings, you may accept purple seedling stems and leaves but quite obviously i didnt and worked at it. Peace

So i see a lot of people have purple stems and wonder how the hell it happens. Well for those who ask the answer is all too often 'GENETICS' or temps. I…

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? ]]>