Yellowing leaves make any orchid grower nervous. The questions are limitless: should you cut off yellow orchid leaves? What does it mean when leaves turn yellow? How do you fix an over watered orchid? How do you fix yellow leaves on plants?
When the leaves on your orchid start to yellow, it’s normal to feel like something is wrong.
When a leaf is older, it will naturally yellow and fall off. Yellowing leaves on your orchid could indicate the end of the natural life cycle. To produce new leaves, the older ones near the base fall off. Before they do, they will turn yellow, then shrivel up slowly. They are unsightly, but it’s best to leave them until the naturally fall off.
This is the only positive reason for yellowing leaves, all the other eight are negative.
If the leaves that are yellowing are the older ones, and no yellowing is occurring on the other leaves, then you’ve nothing to worry about. This is a sure sign that your orchid is growing and the life cycle of that particular leaf is over.
If this is not the case, yellowing leaves may be as sign of several other things, like:
- Too much direct sunlight
- Root Rot
- Low Temperatures
- Too much Fertilizer
- Not the right Fertilizer
- Bacterial or Fungal Infection
Note: If you recently repotted an orchid, changing its potting medium from sphagnum to bark, the orchid might respond by yellowing. This is a natural response, albeit a negative one. Hopefully, the yellow will fade in time and the normal green color will come back. The stress of being changed from its environment is more than it can handle and it temporarily “shuts down.” This is why we only repot when absolutely necessary.
How to Know If Yellowing Leaves in Your Orchid is Natural?
On a Phalaenopsis (moth orchid) and other monopodial orchids, the older leaves will be the largest and closest to the potting medium. On Oncidiums and other sympodial orchids, the yellowing will occur from each oldest pseudobulb.
How many leaves fall off each time? This is easier to answer with a moth orchid. A Phalaenopsis orchid will have one leaf per 10% of humidity in the environment it lives in.
This is why greenhouse orchids, which have around 70-80% humidity, display around 8 gorgeous leaves, four on each side. They are bigger and more developed when compared to the Phals grown at home.
In our home office or living rooms, the humidity is lower, around 40% if you provide a humidifier.
Without a humidifier, household humidity ranges around 25 to 33%. You can except 4 leaves to be the “normal” for these plants. There are exceptions, of course.For all orchids, the bottom leaves (or the leaves originating from the older pseudobulbs, called back-bulbs) will turn yellow first, one at a time during different seasons of the year.
This is a normal part of the life cycle of the orchid. To nurture a leaf that’s dying isn’t the best plan, so the orchid cuts off care the old leaf. A new one emerges on the upper part of the stem.
Should you cut off yellow orchid leaves? I don’t cut off the leaves since that is a way for bacteria and fungus to enter the orchid. A wide-open cut is an invitation for microbes to party, even if you apply cinnamon and all the “works”.
If your orchid is weak or recovering from a hardship, then it might be advisable to cut off the leaf. This saves energy and the orchid can focus on what is more necessary or urgent.
If the leaf that is yellowing is a newer leaf, then you might have another problem, not just an ending life cycle. Let’s look at each possible variable to best determine how to stop the leaf from yellowing.
1. Yellow Leaves May Be a Sign of Too Much Sunlight
If all the leaves are yellowing in uniformity, the cause is something that is affecting the whole plant, and not just one focused location. Sun damage will start off as white smudges, circumference by brown circles. Around this part of the leaf, a yellowing occurs. In this case, the culprit is too much direct sunlight.
Orchids love sunlight, but not direct sun. Not even the “high-light orchids” like direct afternoon sunlight. If your orchid sits in a window sill with sun pouring in directly onto the leaves, it might be a good time to consider moving the orchid.
Phalaenopsis are low-light orchids, and prefer to be in bright light,
but never direct sunlight.In their natural habitat, orchids attached themselves about 1/3 the height of the tree. In these conditions, with extensive foliage over them, direct sunlight almost never reaches the leaves. But tropical rain forests are far from dark. There’s plenty of natural light, and bright conditions are essential for the orchid’s growth.
Without the use of a sheer curtain or partial shades, sun hits the leaves directly. Sun damages the sensitive light-capturing structures in their leaves. Just like we get sunburned, the orchid will sunburn, too.
Overexposure to direct sunlight will cause leaf burn.At first, little yellow spots will appear where sun damage has occurred. If not moved, the orchid will continue to die. Spots will turn into brown smudges. Once burned, the damage will be irreparable for those leaves, which turn yellow, purple or black.
Fixing High Light Problems:
Make sure your orchid is in a well-lit place, but not in direct sun. Even though window sills are beautiful, not many orchids handle direct sun.
East facing windows are the best, because they receive the softer, morning sun, which doesn’t have much intensity. North and west facing windows are also a great bet. These recreates the tropical rainforest perfectly. South-facing windows receive too much sun, so avoid them.
If the yellowing still occurs, move the orchid back, away from the window. Your aim should be bright light, not direct rays. A sheer, transparent curtain might be all you need to keep the harsh rays back.
Yellowing Leaves with Artificial Lights
If you grow your orchid under artificial grow lights, like I do, place Phalaenopsis on a lower shelf, further away from the lights. Moth orchids prefer 1200 to 2000 fc of light. Cattleyas, being medium or intermediate-light orchids, prefer a higher intensity light, from 2000-3000 fc. Vandas prefer more than 3000 fc.
In practical terms, fluorescent lights should be 4-12 inches, closer to the 12 mark. If you use a 400W HID, then install it five feet above the orchid.
Low-light orchids do best with 1200-2000 fc
Medium-light prefer 2000-3000 fc
High-light orchids thrive with 3000 fc
REMINDER: As mentioned before, if only one, older leaf is yellowing, and it happens to be the closest to the potting medium, there is nothing to worry about. Start looking for new growth soon after the leaf has died. Observe the other leaves closely, too.
If you see that the yellowing is not uniform, for example, only 1/3 of the leaves are turning yellow, or it isn’t the oldest leaf, or new growth isn’t occurring, then it’s time to look into the other possible causes quickly.
2. Yellow Leaves Caused by Over-watering
One of the classic signs in any household plant that it’s receiving too much water is that the leaves turn yellow. Orchids follow this pattern, too. The yellowing means a slow loss of the green chlorophyll that keeps it producing energy.
It’s losing its vibrant green color because the chlorophyll is dying—drowning, to be more precise.
This happens because the roots absorb the maximum amount of water they can, not sure when the next watering will happen. Tropical rain is unpredictable and it could be a few days before another rain.
Orchid roots adapted over time to absorb as much water as they can, hydrating the pseudobulb and leaves.
Every time it “rains”, the roots absorbs more water. If the plant is already hydrated, but has nowhere to store it, then in its own way, it starts to drown.
Fixing Yellow Leaves from Over watering
More precisely, how do you know when is a good time to water? You can check out another article here, but for the short answer, push your finger down a little way into the potting medium. If it’s humid, don’t water. Wait a day and test again. Let the orchid dry out completely before attempting to water again.
If your orchid is severely over watered, and you have a feeling that the medium will take a horrendous amount of time to dry, you can try a more drastic method in attempts to save the roots. Unpot the orchid and leave the roots in the bare air for two days, or even more. Remove all the potting medium.
Yes, that’s right—all of the medium.
This isn’t as radical as it first seems because orchids live attached to bark on the trees with no potting medium whatsoever. Your orchid will not suffer with this extreme method as much as you think it will. We have that idea because we associate orchids to household plants that use soil.
After a few days of complete air, the roots should look better. The leaves may or may not come back from the yellowish-brown color, since too much damage has been done to the internal structure of the leaf. But you might be able to salvage the orchid itself, losing only one or two leaves.
3. Yellow Leaves Can Be Caused by Root Rot
Another problem commonly related to over watering is root rot. It’s good practice to check your potting medium regularly (or use plastic, transparent pots), verifying the quality of the roots, drainage, air circulation inside the pot, and the compactness of the potting medium.
If the roots aren’t being able to perform adequate absorption of nutrients and hydration, then your orchid will suffer. In this case, all the leaves will start to turn colors, and not just one or another leaf.
Root rot is mainly caused by poor drainage. The potting medium breaks down in time, raising the alkalinity in the potting medium. This releases a chain reaction, which destroys the orchid roots in every step.
Fixing Yellow Roots Caused By Root Rot
Take the orchid out of its potting medium and change mixes urgently. Cut the dead roots off, and spray the orchid with hydrogen peroxide to kill some of the bacteria buildup from the root rot.
Make sure your orchid has proper air circulation inside the potting medium, and not just on the leaves. Keep a fan on, even during the night.
Root rot is not impossible to cure, if the orchid has some good rots and you take the time of care for it.
4. Yellowing Leaves Caused By Nutrient Deficiency
Some fertilizers are excellent for orchids; others lack quite a bit. Sometimes the potting medium will absorb more of the nutrients, leaving less for the orchid. In other circumstances, the quality of the water you use to water your orchids will have a direct effect on the color of the leaves.
Why does lack of nutrition turn the leaf yellow? Without proper nutrition, the chlorophyll dies off. This process is called Chlorosis. Chlorophyll is naturally dark green and gives the green color in plants. When it dies, the orchid turns to a yellow mushy color.
In any case, it’s known that the lack of both iron and nitrogen will turn the orchid leaves yellow.
If in fact the cause is a nutrition deficit, the yellowing will be seen on the pseudobulb, too.Make sure that your fertilizer has a balanced N-P-K. This is better done at your local store, to verify what fertilizers they have and can recommend to you.
5. Cold Temperatures also cause Yellow Leaves
Orchids are found naturally in temperatures that range from 65ºF to 85ºF, sometimes a bit higher than that. Never lower. In the USA, the temperatures are mostly too cold for orchids to live by themselves outside, unless you live in the deep south.
If your orchid sits by the window and gets chilly air that is in the lower forties, the leaves may tell you that it’s unsatisfied by turning yellow.
This can also happen if you buy your orchid in the winter. Just the transport from the garden center/shop to your car and the ride home, can be sufficient to damage the leaves. If the time it’s exposed is too long, the yellowing might not be fixable. The leaf will just shrivel, wither, turn yellow, and eventually die.
There are orchids that are considered cooler-orchids, which prefer cooler temperatures. Yet, cooler means cooler compared to the tropical climates in the rain forest, not the cooler temperatures of our climate. (By our, I’m referring to the USA, since I currently live in Kansas.)
Good temperatures for an orchid are 65ºF to 80ºF (18ºC to 26ºC) during the day
and 60ºF to 70ºF (15ºC to 21ºC) at night.
If it gets too cold, the first sign will be droopy blooms. The buds will close, and finally, the leaves will yellow then brown. All orchids need a cooler temperature at night, which is a drop in the daytime temperature of around 10 to 15 degrees F. Don’t let the nightly drop in temperature go below 60ºF (15ºC).
Fixing Yellow Leaves from Cooler Temperatures
If it was only one night that the leaves were exposed to cooler temperatures, they might be salvageable. Unfortunately, the buds and blossom won’t. Exposure to cooler degrees is the number one cause for bud blast, by the way.
Move your orchid away from the draft coming from the window, and keep the night temperatures down, but not all the way down.
If it was caused from transport during winter, then the chances of recovery are even slimmer. The leaf will most probably fall off after it yellows. Provide an environment that is constant for the next few weeks and your orchid will adapt eventually with a new leaf growth.
6. Yellow Leaves Can be Caused by Too High Temperatures
On the other side of the spectrum, or should I say thermometer, yellow leaves can be caused by overheating, too. If the temperatures are too high for your orchid the stomata remain closed. Stomata are the pores which gas exchanges occur. They are found, for the most part, on the underside of the leaf, but to less extent, can be found on the upper side, too.
Orchids “breath” at night, when humidity is higher and the cooler temperatures are in favor of gas exchange. If the temperatures never drop during night, or remain too high during the day, the leaves may overheat. The stomata remain closed, preventing the loss the humidity, but also impair the carbon dioxide and oxygen trade off.
Fixing Yellow Leaves by Temperature
Make sure that at night you turn off your heater (if in winter) in order to provide the temperature drop at night.
During summer, make sure the fan is on (for ventilation purposes, too) so the leaf can be cooled.If your orchid is in the window sill, it may need to be set back away a bit. Even though it might not be getting direct sunlight, the higher temperatures during the afternoon might be too much for it.
If you grow orchids under artificial light, make sure that the lights are more than 4 inches away from the top of the leaf. LED grow lights don’t have this problem, but fluorescent lights and HID heat up quite a bit.
7. Too Much Fertilizer can Turn the Orchid Leaves Yellow
You should be fertilizing weekly, or every other week during active growth in your orchid. During rest periods, you can fertilize once a month. If you fertilize too much, the chemicals will build up in the potting medium and contaminate it.
Some fertilizers can be applied with a mist. This is a perfectly good method, but be careful to not allow the water to build up and sit on the leaves. If this happens, small black dots will appear where the water spots were. They turn the leaf yellow if a vast area of the leaf has spotted.
The black dots appear because the leaf cannot breathe, and the chemical build-up prevent the pores from performing gas exchange. This suffocates the cell.
The best fertilizer—and this is my opinion, of course—is one that can be mixed in with water and used after a normal watering cycle. This way, there’s no build up or chemical reaction on the top of the leaves. If you’d like to read more about fertilizers, check out his article.
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8. Yellow Leaves Caused By Disease
This is the most dangerous cause. Although quite easy to diagnose, it’s quite hard to treat. You can check out several signs and symptoms of each particular disease.
Fungus, bacteria, and virus are all treated differently since they are different organisms. I won’t go into detail here about each of the different diseases, but if you have checked every other variable above and none seem to be the problem, there’s a good chance your yellow leaf problem is a fungus. With these eight tips, you should be able to identify the cause of the yellowing in your orchid leaves and treat it promptly.
If this article was of any help, please leave a comment below. I love to interact with other orchid growers and enthusiast, no matter what the level of expertise. We all can learn something new.