Most leaves will turn red when the temperature drops near mid-autumn and the cooler air floats through the cities and towns. This beautiful scenery doesn’t happen with orchids, and if your orchid leaf is turning red, then your orchid is signaling a problem.
Orchid leaves will turn red because of lack of phosphorous, poor soil, fluctuating temperatures, too close to the light source, and improper irrigation. Red Orchid leaves always indicate that the orchid is stressed.
Orchid leaves, unlike most flowering plants, will not turn red since orchids live in tropical and subtropical climates where there is no temperature fluctuation. They grow at higher temperatures year-round.
In each one of these reasons, the underlying cause needs to be fixed or your orchid’s leaf will continue to turn dark red, purple, black, or extremely yellow and die off. In all these cases, the reddening color of your orchid leaf indicates that you need to act soon. Let’s look at each one of these closer to identify the reason your orchid leaf is turning red.
1) Lack of Phosphorous Turns the Orchid Leaves Red
The lack of proper nutrition in the soil will lead to a reddening of the orchid leaf. In particular, the element that is missing is phosphorous. This is the 2nd element in the NPK ratio identified when you look at fertilizer. What leads the orchid leaf to turn red is the sugar build up in the leaf. These are not distributed properly (or poorly) due to the lack of phosphorous.
Phosphorous is the main energy building component in ATP, which breaks down to ADP releasing phosphorous. With this element, the orchid cells store energy and use it to distribute nutrients to the leaf, flower spike, and roots.
Without the energy to distribute the right nutrition in the plant cells, the sugars build up inside the orchid leaf. This breaks down chlorophyll in time, which is responsible for the green pigment.
Chlorophyll absorbs light from the sun (or as in my case, the grow light) and transforms that into ATP. With less ATP, there is less energy. It’s a domino effect that only brings negative consequences, each time getting worse.
The older orchid leaves will display this reddening first before new leaves do. This is because the orchid channels it’s nutrients to the younger growth, leaving the older to take the hit.
If you do not change the fertilization methods or the percentage of Phosphorous in your fertilizer, your orchid’s newer leaves will also present this reddening, and your entire orchid is suffering.
2) Poor Soil Conditions Turn Orchid Leaves Red
I had thought about dividing this section into smaller sections but later decided not to. All the reasons point to the one underlying point: you need to repot. Either way, the lack of good potting medium will lead to the orchid’s leaves turning red, and it’s easily fixed.
2A) Poor Orchid Potting Media Lower the PH
The first consequence of poor potting medium is that it will decrease the pH, which turns the leaves red. Most orchids do best in a potting medium that has a range of 5.5 to 6.5 on the pH scale.
If your orchid is terrestrial, this might be a little lower, due to the high quantity of acidic material found in leaf litter and mosses. If your orchid attaches to rocks, the calcium carbonate trickles down rock and raises the pH slightly, around 6.5 to 7.5.
If your orchid is sensitive to pH fluctuations, you’ll want to change your potting medium more frequently, as in 2x a year. If you have it planted in pure sphagnum moss and no orchid bark, you’ll need to change it yearly.
The issue with a pH that is too low is that the capability of the rots absorbing minerals and essential elements for survival decline. Orchid roots lose 30% of their capacity to absorb phosphorous when the pH is too low. This means that you can fertilize all you want, but the roots will not be able to retain those minerals and you’ll be wasting both your time and money.
2B) Poor Orchid Potting Media Hinders Good Drainage
The second issue with poor soil is that the drainage will not be as good or fast as with a potting medium that is newer. Constant water around the roots will turn the orchid leaves a sickly red color.
Orchids are accustomed to being on trees, where they get abundant rain but dry off quickly.
They do not like to be around the presence of water all the time. They certainly aren’t aquatic plants, even though some like to have extremely high humidity (like Masdevallias with 80%). Yet higher humidity doesn’t mean there is water 80% of the time around the orchid roots.
If your potting medium has become compacted due to extended periods of time inside the pot, then water might take a long time to enter and exit the pot. Quick drainage is the goal in all potting media.
Orchid bark degrades extremely fast and even if it is made from hardwood, this time is not “forever”. Unlike houseplants, the potting medium needs to be changed regularly so water can flow through the pot and exit.
2C) Poor Orchid Potting Media Prevents Good Airflow
The third issue with poor soil, (I’m calling it poor soil because potting media can be so many things from Styrofoam peanuts, leca pebbles, river rock, lava rock, perlite, charcoal, and so many other items) is closely related to the last item. If there is no water flow due to compacted medium, then there certainly isn’t any air flowing inside the pot. Lack of airflow turns orchid leaves red.
The lack of oxygen, hydrogen, and nitrogen inside the orchid pot will suffocate the orchid roots. Without the proper airflow, the roots will die off. If there are no roots, then no nutrients are being absorbed and transported to the orchid so it can survive.
In all these 3 cases, the poor orchid potting media contributes to the orchid leaves turning red. The leaves will not be a bright, vibrant red, but a molted sickly color that takes a good eye to detect. The signs are present but very subtle.
Then one morning, you wake up and check your orchids, and—sad surprise.
It’s always a good idea to learn how to verify the signs and symptoms of orchid problems as you take care of your orchid. As in health care, the earlier you can catch some of the problems, the better it is to treat.
3) Temperatures Cause Orchid Leaves to Turn Red
Even though the orchid does not follow the cooler signs in autumn and contribute to the fall foliage colors, the cooler temperatures affect the orchid. Cold temperatures are not found where orchids live (the majority of them at least) and orchids are not frost-hardy.
Most orchids live in a climate where temperatures are relatively pleasant to a bit hot, and sunlight is available year-round. These tropical rainforests, subtropical jungles, and hot and humid habitats do not present cold weather ever. The orchid has no idea what cold is (unless you water it with ice cubes and I do NOT recommend that).
I had a hard time with this as an adult, since I had lived overseas for the majority of my life. When I returned to Kansas the winter season brought me down to near depression levels. I couldn’t stand waking up and not seeing green and also feeling cold all the time. There is no level of long-johns that take away cold. Orchids react more or less the same way I do to cold weather—they clam up.
The reddening in the orchid leaf due to cold weather is caused by the dying of the green chlorophyll. This could have happened because of an extreme switch in temperature suddenly, where the orchid was used to living in one climate and you took it outside. The cool drafts of wind can cause the chlorophyll to undergo temperature shock and die.
This also happens toward the end of the autumn season, where if you have your orchids outside and are on the edge of bringing them inside for the nearing winter. If the nighttime temperature drops too much, your orchid leaf could take the hit. Always keep an eye on the weather a few days beforehand.
I had a terrible experience (at least it wasn’t with an orchid) but I left my household plants out in April when the weather was extremely nice. One night—that was all it took. Out of the blue, the weather dropped 50 degrees.
I killed all those plants and swore never more to take my plants outside in Kansas, where the weather is unpredictable. I did some research about that though, to see if Phalaenopsis could really live outside. This article about planting orchids outside was the byproduct of what I discovered.
But back to cold temperatures… Orchids have a similar growth pattern to succulents and a lot of what you read about succulents can be applied to orchid care. Not all, but a lot. One of these signs in reddening succulent leaves is due to watering with colder water.
I have not found an article (printed or published) that will confirm this same finding with orchids, but I believe the principle is the same. If cold temperatures on the leaves will turn the orchid leaves red, then it could be assumed that the cold water on the root tips would have some side effect, too.
4) Red Leaves on Orchids Are Caused By Too Much Light
When the light source is too close to the leaf, the result is reddening in the orchid leaf. The red color is natural sunscreen protection, called anthocyanin. This purple-colored freckle will spot the entire leaf that is in direct contact with the sunlight.
The red tones in this leaf are closer to purple and will go away if you move the orchid to a lower light area. If your dots are more purple than red and you feel like it’s’ not the light that is the culprit, then check out this article where I explained the reasons for the orchid leaf turning purple.
The orchid doesn’t have to be moved if you like it where it is. The reddish-purple dots will indicate it is still in the tolerance zone but is dealing with the highest threshold it can manage.
Any higher than this, the leaves will sunburn. Make sure you do not apply anything, like lemon juice, to the orchid leaves when it has these purple dots when cleaning. The lemon will create a chemical reaction with the light and damage your orchid leaf beyond repair.
If you want to clean you orchid leaves with products that don’t sunburn the leaves, take a look at this article where I explain several ideas of homemade cleaning products that make the leaves shine.
These red spots are not weak points in your orchid. There is no need to become worried that infection of bacteria can enter these wounds because they aren’t wounds. They are just chemicals that have formed due to the higher light to protect the leaf from any damage.
5) Improper Irrigation Causes Red Orchid Leaves
In this point, the reddening of the orchid leaf could be both due to underwatering or overwatering. So whatever the case, improper watering will damage the leaf in the long run.
By underwatering your orchid, the nutrients cannot reach the furthest point in the leaves and they start to die off. The first to die is the chlorophyll as mentioned before and the leaf loses its green color. This could leave behind yellowish-red color. In time, this reddening will turn brown and crunchy. The red is just the first sign the orchid leaf is not well.
By overwatering, the roots die off and bacteria quickly take over the pot. This is a common problem when dealing with orchids that go dormant. I tend to forget that I need to be watering less and drench the poor orchid before I even realize that this orchid will not absorb what I’m providing. Then it’s too late.
The water sits in the potting medium and is absorbed by the orchid bark and sphagnum moss yet when released slowly, the roots will not absorb it. The roots sit in water for a long, long time, causing them to rot.
If you need a little help with understanding dormancy, I suggest these 2 articles: in this one I explain dormancy, and in this one I explain how to water a Catasetum orchid, which has a long dormancy period.These are the overall causes of your orchid leaf turning red: lack of phosphorous, poor potting medium, cold air or temperature fluctuations, or improper irrigation. In all these cases, the plant is stressed and needs to be helped so it can go on to produce a beautiful bloom.
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Below are the articles I mentioned during the course of this tutorial. I mention them here again because I always found it hard to go back and find the article I wanted to read after I was done.
–How to Water a Catasetum Orchid
If you have found this article helpful, please comment below. It’s always great to interact with other orchid enthusiasts, be it a beginner level or more experienced. I by no means am an expert since there isn’t an orchid I can’t kill. We are always learning on this path of orchid care and I certainly am learning tons of new information about how to grow orchids indoors, which is a new thing for me.
I wish you the best in your orchid care! Happy cultivating!