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Your cilantro plant turning purple is usually a sign of stress, and the most common culprit is cold temperatures.
When cilantro plants turn purple, it often means the plant is reacting to environmental stress rather than a disease or pest problem.
If you’ve been wondering why your cilantro plant is turning purple, you’re in the right place.
In this post, we’ll explore the reasons your cilantro plant is turning purple and how to fix it so your herb thrives again.
Why Is My Cilantro Plant Turning Purple?
Cilantro plants turn purple mainly because of cold stress, but there are several other reasons this color change happens.
Here’s what’s going on when your cilantro plant starts showing purple leaves and stems.
1. Cold Temperatures Trigger Purple Pigments
Cilantro is a cool-season herb, but it still has its limits.
When temperatures drop below 50°F (10°C), cilantro plants can start turning purple.
This happens because the cold causes anthocyanins, which are purple and red pigments, to build up in the plant tissues.
It’s actually a protective response, kind of like the plant putting on a tiny purple sweater.
If your cilantro plant is turning purple after a cold snap, this is almost certainly the reason.
2. Phosphorus Deficiency
A phosphorus deficiency can also make your cilantro plant turn purple.
Phosphorus helps plants with energy transfer and root development.
When cilantro plants can’t get enough phosphorus, the leaves and stems often take on a purple or dark reddish hue.
Purple leaves on cilantro due to phosphorus deficiency usually start on older leaves first.
If the soil is too acidic, too cold, or too wet, the plant may struggle to absorb phosphorus even if it’s present in the soil.
3. Soil That’s Too Wet or Poorly Drained
Overwatering is a sneaky cause of a cilantro plant turning purple.
When cilantro roots sit in soggy soil, they can’t take up nutrients properly, especially phosphorus.
This nutrient lockout leads to the same purple discoloration you’d see with a straightforward deficiency.
If your cilantro plant is turning purple and the soil feels like a wet sponge, let it dry out before watering again.
4. Natural Maturity and Bolting
As cilantro plants get older, they naturally start to bolt, which means they send up a flower stalk.
During this stage, the stems and leaves can develop a purple tint.
If your cilantro plant turning purple comes with tall stems and small white flowers, it’s just bolting.
Once cilantro bolts, the leaves also turn feathery and the flavor gets bitter.
This is a natural part of the cilantro life cycle and not something you can reverse.
5. Sunburn or Heat Stress
While cold is the usual suspect, intense heat and strong sunlight can also stress cilantro.
A cilantro plant turning purple after a sudden heatwave or too much direct afternoon sun is showing signs of stress.
The plant produces anthocyanins as a sunscreen to protect itself from UV damage.
So if your cilantro plant is turning purple in the middle of summer, heat stress could be the reason.
How to Fix a Cilantro Plant Turning Purple
Fixing a cilantro plant turning purple depends on what’s causing the color change.
Here are practical steps you can take to bring your cilantro back to green.
1. Protect Cilantro From Cold
If cold is the issue, cover your cilantro plants with a frost cloth or bring potted cilantro indoors when temperatures dip.
Mulching around the base of the plant also helps insulate the soil and roots.
A cilantro plant turning purple from cold stress will often green back up once temperatures warm up again.
2. Adjust Your Watering Schedule
Let the top inch of soil dry out between waterings.
Cilantro likes consistent moisture, but not soggy roots.
If your cilantro plant is turning purple because of overwatering, improving drainage can make a big difference.
3. Feed With a Balanced Fertilizer
A phosphorus deficiency can be corrected with a balanced fertilizer or a phosphorus-rich blend.
Look for a fertilizer with a higher middle number, like 10-20-10.
If your cilantro plant turning purple is due to poor nutrient uptake, check the soil pH too.
Cilantro prefers soil with a pH between 6.2 and 6.8.
4. Provide Afternoon Shade
If heat stress is making your cilantro plant turn purple, give it some afternoon shade.
A spot that gets morning sun and afternoon shade is ideal for cilantro in hot climates.
This simple change can stop a cilantro plant from turning purple due to sunburn.
5. Harvest and Replant If It’s Bolting
Once cilantro bolts, there’s no going back.
If your cilantro plant is turning purple because it’s bolting, harvest what you can and replant.
Sow new cilantro seeds every few weeks for a continuous supply of fresh green leaves.
So, Why Is Your Cilantro Plant Turning Purple?
Your cilantro plant turning purple is usually caused by cold stress, but phosphorus deficiency, overwatering, heat stress, or natural bolting can also be to blame.
A cilantro plant turning purple isn’t always a death sentence.
Often, a few simple adjustments to temperature, watering, and feeding will bring the green back.
If your cilantro plant is turning purple because it’s bolting, enjoy the flowers and start a new batch.
Either way, now you know exactly why your cilantro plant is turning purple and what to do about it.