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My cannabis has purple stems!

Q: Hey Nebula! My 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?

A: When a marijuana plant or seedling has a purple stem, it almost always is the result of genetics. Some strains just grow that way when they're young.
Wait a week or two before making any alterations. The plant should turn green soon.