Most indoor gardeners love herbs that grow easily. And who doesn’t love the scent of fresh oregano? So, when oregano leaves turn purple, question marks abound. Why is this happening? Why are the leaves purple? Is my oregano dying? What can I do?
Oregano leaves are green, but some are naturally purple. At the same time, green oregano leaves can turn purple due to stresses caused by 1) nutrition imbalance, 2) temperature trauma, 3) humidity or moisture issues, or 4) pruning trauma.
We love oregano leaves for its fresh, green smell. However, when green oregano leaves turn red, purple, or violet, we may not know why the plant is showing signs of stress: Is it due to changes in soil nutrition, air temperature, or rough harvesting?
Or is it for natural reasons that we need not worry about? Let’s start with that.
Table of Contents
- 1 1. Natural Color – No Action Required
- 2 2. Cold Protection – No Action Required
- 3 3. Dehydration Or Poor Drainage – Control The Moisture
- 4 4. Nutritional Imbalance – Enhance The Soil
- 5 Bonus Tip: Harvesting Trauma – Just Do It (With Care)
- 6 Extra Bonus: Why We Really Love Oregano (Hint: It’s Chemical)
- 7 Takeaways
- 8 Sources
Not all oreganos are green. For instance, Greek oregano has leaves that show purple tints. Some oregano plants, such as Herrenhausen (laevigatum), have purple leaves.
On the other hand, if you peek under the leaves of O. aureum, you’ll see that the leaves are purple underneath. That’s natural.
So, the next time you notice the color purple on your oregano leaves, do a little research. Most oregano seeds are available online as Cuban oregano, Italian oregano (here on Amazon), or wild zaatar oregano (here on Amazon).
Find out if your oregano plant is a type with natural purple coloring on its leaves. (Don’t be confused by the purple oregano, also called Hopley’s Purple, which has green leaves and purple flowers.)
PRO TIP: Hopley’s oregano has fragrant, deep green leaves that turn reddish-purple when the weather cools below 65*F in autumn.
However, if your oregano leaves are really supposed to be naturally green but they’re turning purple, this article explains why, and what you can do.
When young leaves, particularly small ones and seedlings, are getting too much sun, they protect themselves from sun damage by producing anthocyanin, a natural pigment.
How does it work?
Normally, sugars move freely through plants. When the heat goes up in the summer, these sugars can build up and produce anthocyanins, which are reddish or purplish pigments that absorb green and yellow light to prevent sun damage.
As a result, the tender leaves can still photosynthesize and their chlorophyll still functions. In short, they’re still normal leaves except that they have natural sunscreen. This is a good thing that you need not worry about.
However, when your oregano leaves are purple underneath, that’s another story. Why does this happen?
Some say that this is to protect the leaves from fungus, herbivores, or insects. Others say that it’s a protection from sunlight reflecting from other leaves and lighting the undersides of leaves. The fact is, no one is really sure why.
But the next natural phenomenon is demystified: why oregano leaves turn purple in winter.
When green oregano turns purple in winter, is not dying. The color purple is part of a natural process in the plant’s stress cycle, particularly when the low temperature causes sugar in the plant to stop moving and build up on the leaves.
Many gardeners confirm that the leaves of Greek oregano turn purple in the fall. At the same time, research tells us why oregano leaves of the compactum or humile variety turn purple in winter.
It is known by the scientific community that several varieties of oregano turn purple in the fall due to sudden changes of temperature in the soil and the air, which causes nutrient unbalance.
For instance, when temperatures drop and the soil cools in the fall, we see a lot of green leaves turning yellow, orange, red, or purple. This is natural.
However, if you’re growing oregano indoors, you can control the temperature and protect your plants from the cold.
To help you address temperature issues a grow light with temperature control as this one on Amazon connected to your cellphone.
Oregano originally comes from the Mediterranean where there is sunshine year-round, the soil is well-drained, and there is good air circulation. When any of these is lacking in your oregano’s growing environment, the plant gets stressed out.
One sign of stress in plants is discoloration of leaves – and even stems – turning dark brown, black, or purple. Stress interrupts normal plant functions and increases the purple pigments called anthocyanin.
For instance, anything that dehydrates the roots and tissues of your oregano plant can create purple or red leaves.
Another important cause of oregano stress and purple leaves is the presence of compacted and poorly drained soil. This limits the flow of important nutrients and water from the roots to the leaves.
However, diagnosing this correctly is not always that easy: such pigment buildup can also be caused by drought, diseases, and cool temperatures.
For instance, another cause of stress is poor drainage, which can accumulate fertilizer salt in the soil. These salts can draw water away from the roots of your oregano plant, similar to drought, and red or purple leaves appear.
To help you address these issues, try using pots with drainage holes (this is a good one on Amazon).
4. Nutritional Imbalance – Enhance The Soil
Normally, oregano leaves are green-yellow. When they turn purple, it may indicate a lack of phosphorus. The leaves may even turn dark green or a deep purple color that’s almost black, particularly on tips and edges.
A little compost or a phosphorus additive for the soil can help you address the issue. Keep in mind that phosphorus (P) is necessary for plants — particularly young plants — to produce nucleic acids, sugars, and energy.
But nutrient deficiencies in plants are often hard to spot and diagnose correctly. This is because the signs can be confused with the symptoms of insect damage, disease, too much fertilizer, poor soil, or poor drainage. Temperature also plays a large role.
Extremes of high heat followed by air that’s too cool can cause nutrient imbalances and your oregano may show a lack of phosphorus.
If you’re growing oregano on patios, decks, or pots exposed to external temperatures, you can bring them inside. You can also enrich the soil by adding some rock phosphate such as this one on Amazon, bone meal like this one on Amazon, or phosphorus fertilizer like this one, also on Amazon.
When plant tissue is broken, the color purple is part of a natural process in the plant’s stress cycle, particularly when the plant is repairing the damaged areas by shutting down the cells that are dead and cannot be revived.
Many times, we simply pluck out the leaves from our oregano plants to use in a dish or to treat a persistent cough. We may not be aware that the way we harvest those leaves might be hurting the plant unnecessarily.
When you pluck leaves, you leave a “wound” or a traumatized area on the plant. This creates a stress on the plant. The wound turns black or purple in the healing process.
So how can we harvest oregano leaves without causing unnecessary stress to the oregano plant? Here are key pointers to keep in mind:
Keep it clean: If you’re using your fingers to pluck off leaves, wash your hands before doing so. This way, you can minimize contaminating the plant and help it heal faster.
Be gentle: Plants are living things like us. They respond to pain. The first thing is to be gentle. Avoid crushing or damaging any part of the plant while you pick leaves. To help promote healing of plant wounds, you can check out a biological plant wound dressing such as this one on Amazon, or a pruning sealer such as this one, also on Amazon.
Use a sharp blade: Make clean cuts by using a sharp blade, knife, scissors, or pruners. Don’t break off stems, and never tear off leaves. Check out some online plant clippers such as this one on Amazon, trimmers like these on Amazon, or pruning shears like this one, also on Amazon. Always make sure that blades are sharp to make fast and clean cuts that minimize trauma to the plant.
Cut the outermost node: Whenever you harvest leaves from your indoor oregano plant, cut right at that soft joint where the leaf meets the stem. If you want a bushier plant with more leaves, make a clean cut-off from the top part of the stem.
Time it right: It is best to harvest early in the day, when the dew on the leaves have dried, and before the temperature gets hot. Savvy gardeners recommend that you harvest your herbs when they’re not flowering or after the flower buds have opened.
Many old folks say that oregano represents humility or modesty because it can grow and thrive with little care, even in dry, stony, or sandy soil.
The word “oregano” is Latin and comes from the Greek for “joy of the mountains.” According to ancient Greek mythology, the goddess of love gave oregano to humans to give them joy.
Even today, some traditional cultures crown a bride with an oregano wreath to symbolize happiness and to banish sorrow.
But there’s a pragmatic side to this story.
For hundreds of years, humans have been using oregano plants for cooking and for medicinal purposes. For instance, old folks would recommend chewing fresh oregano leaves to relieve toothache, a lingering cough, or even indigestion.
Today’s younger generations know oregano as a pizza topping, enhancing a vinaigrette, or green flecks in a barbecue marinade.
Although oregano is used mostly as a food seasoning and as a traditional herbal treatment, science is particularly in love with oregano for its potential in herbal treatments, food flavorings, and food additives.
Science also tells us that love and attraction is a chemical thing. Likewise, our love for the culinary oregano is based on three chemicals: carvacrol, sabinene hydrate, and thymol.
Thymol – This is a natural chemical in oregano that can protect against some poisons as well as provide treatment against fungal infections, viruses, and tuberculosis such as this one on Amazon, or this one, also on Amazon. Thymol is also used as a natural repellent as well as a general disinfectant.
Carvacrol – This is a chemical that gives us a pungent, peppery flavor in pizza. (The tastiest types of oregano are Greek oregano and Italian oregano, which have the highest carvacrol content.) In addition to that, carvacrol like this one on Amazon or this one, also on Amazon, is also an effective antifungal and antibacterial agent.
Sabinene hydrate – This is a natural chemical in oregano that produces a balsamic and woody scent that is valued by manufacturers of scented products such as household cleaners, soaps, shampoos, ointments, lotions, and perfumes. Trans-sabinene hydrate is the main essential oil ingredient in this product on Amazon, as well as in this one, also from Amazon.
Back to our main topic, you’re done! You know now why oregano leaves show the color purple! Before you go, here are key takeaways for you to remember easily.
Oregano is an essential oil producer, a comfort food enhancer, and an emergency treatment for some common pains and aches. If you’re concerned about your naturally green oregano leaves turning purple, here’s why and what to do:
It’s a natural thing: Check and find out if your oregano plant is a variety (there are at least 10 common types) with naturally purple leaves. If the answer is yes, then you can relax. No action is required.
Sun damage protection: Small and young oregano leaves turn purple as protection from sun damage. This is a natural process that you can let be. If, however, you want to take some kind action (some of us are like that), then you can bring your plants inside or provide them with some shade.
Winter cold protection: Many varieties of oregano naturally turn purple when stressed out by low temperatures. This has been going on for centuries, so you don’t need to worry. However, you can also bring your oregano plants indoors.
Dehydration or poor drainage: Too little or too much water can stress out your oregano plant and it’s the stress that turns leaves purple. To address a compacted soil issue, change the plant to a bigger pot or better soil. Or if the soil is fine, you can time your watering to fit your plant’s needs.
Nutrition deficiency: Lack of phosphorus can stress out your oregano plants, and purple or reddish leaves are indicators. A little bone meal or phosphorus fertilizer should solve the problem but, first, make sure that this is really the problem.
Harvest trauma: Rough handling and unnecessary damage when harvesting or plucking oregano leaves can traumatize the entire plant. The black or purple areas indicate stress as well as a natural healing process. The best you can do when harvesting is to keep your hands clean, your pruning blades sharp, and to cut in the right places at the right time.
I hope that this article helps you as much as it has helped me and my friends. If you have experiences to share, or if you have questions about why oregano leaves show the color purple, please let me know. I’d love to hear from you.
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“A taxonomic revision of the Genus Origanum” by J.H. Ietswaart, Vrije University
“Oregano: the mountain of joy on taste buds” by D. J, Sen, World Journal of Pharmaceutical Sciences
Growing Herbs at Home by D. H. Trinklein, University of Missouri Extension
10 Reasons to Grow Oregano: a Highly Beneficial Herb by C. Codekas at Grow Forage Cook Ferment
“Why do some plants have purple leaves?” by the Dunedin Botanic Gardens in Otago Daily Times
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“Essential Oils of Oregano: Biological Activity beyond Their Antimicrobial Properties” by N. Leyva-Lopez et al in Molecules
“Top plants containing trans-sabinene-hydrate” by Natural Medicine Facts
“Essential Oil Compounds of Origanum vulgare from Corsica” by B. Lucas et al, in Natural Product Communications (NPC).
“Origanum laevigatum Herrenhausen” by the Missouri Botanical Garden
“Oregano: How to Care for this Amazing Aromatic Herb” by M. Iseli in Plantophiles
“Oregano oils” by L. A. Ortega-Ramirez, et al in Essential oils in food preservation, flavor and safety, Academic Press