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

by Nebula Haze

Purple stem on cannabis plant - is this a nutrient problem, how do I fix it?Question: 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. Some cannabis strains just naturally tend to grow with purple stems, especially when seedlings are young, or when the plants get cooler temperatures at night.

Wait a week or two before making any alterations if your plant otherwise appears healthy. The stems should turn green soon in most cases. As long as your leaves are healthy and you have no other symptoms, you usually don't need to worry about purple stems.

If you believe there is a nutrient problem with your cannabis plant, for example if the plant is also growing slowly or the leaves are discolored, then the plant may have a magnesium deficiency, which occasionally can cause purple stems. If so, the problem is easily fixed with the addition of a bit of extra magnesium in the next watering.

Good sources for adding magnesium include:

  • Cal-Mag
  • Epsom salt (dissolve 1 tablespoon per gallon / 4 ml per liter)
  • A good cannabis-friendly nutrient system will contain just the right amount of magnesium needed by cannabis plants



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