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I've seen many people in one of my local forums say that their purple basil turned green a while after planting. There were no proper conclusions to this problem, so could someone please explain?

In my own experience, I planted a purple basil from seed. It started with purple leaves until it was medium sized, and then its leaves started to turn green.

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I do not have personal experience with this, but based on some discussion here it looks like the hybrids that generate purple basil can at times be unstable and revert to the traditional green basil.

The plant's hybrid parentage may cause its genetic instability when grown from seed; leaf color often varies from plant to plant and large numbers of pure green plants maybe be produced.

Another possibility mentioned on that page is that they will sometimes revert if they do not get enough sun.

Finally from here there is at least one type of basil that starts out purple and turns green as it matures: African Blue Basil.

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I put mine into the sun: full sun. After 24 hours, well, maybe I should have taken a before and after photo, but it appears to be more purple to me. Will update in a week. Also, added more herb food to the base of the plant. Try both! Why not... The more food your plants have, the more nutrients your body will have as you eat your homegrown food.

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The purple color is caused by retinal which is the precursor of chlorophyll. Chlorophyll is way more effective at processing sunlight then retinal which is why plants ultimately replaced it with chlorophyll. Move your basil to a sunnier area and this shouldn't happen, but also having sweet basil (green) near purple basil will cause it to change as chlorophyll is a dominant gene while retinal is recessive.

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    Erm, planting a purple basil next to a green one won't affect the two existing plants - but could have some effect on their offspring in terms of genetic inheritence, Hunter, is that what you're saying? – Bamboo Jul 7 '16 at 16:25
  • Just guessing, he could be implying that the strongly dominant expression of the chlorophyll trait in one plant would somehow effect the nearby plant to also produce more chlorophyll and less retinal. This happens with humans too ... put a bunch of guys together in a room than if two start fighting the rest will have their testosterone rise. – jbord39 Jun 10 '17 at 15:24
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I bought a purple basil plant this year just to try because it was so pretty along with several packets of purple basil seeds. The plant has done well, is in full sun, and a good 10' from my green sweet basil but it has turned as well. Interestingly, the seed pods and flowers are all still purple but most of the leaves have greened considerably. It is still pretty and smells amazing but I have also wondered what causes that. enter image description here

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