One of the main ways orchids communicate what is happening to them is through the color change. Their leaves, roots, stems, and flower spikes can all change colors, displaying the most varied differences in what should be normal.
If an orchid produces a flower spike and it turns into a pale yellow, either the potting medium and environment are too dry, it is suffering from nutrient deficiency, an extreme change in temperature suddenly affected the blossoms, high concentrations of elements in the water supply, presence of ethylene gas in the environment, and it might indicate a normal decaying process.
Yellowing Orchid Stem VS Yellowing Orchid Spike
Before I go into each of the seven reasons that orchids will turn yellow, there is one major topic I need to get out of the way. If you research this on google and other platforms, the terms “stem” and “spike” are shown in the results interchangeably as if they were the same.
Even though these are not the equivalent part of the orchid, the search results will treat them the same way. Even worse—some of the blogger’s answers will treat them the same, as in stating “you need to cut the stem back to the last flowering node”.
No wonder Google is confused.
If you cut the stem of a Phalaenopsis orchid, you will be creating cuttings and potentially exposing your orchid to damage from which it might not recover. The technical term for this process is called topping, and you can read about it in this article I wrote about myth-busting orchid propagation.
The stem of the orchid, when referring to a monopodial orchid, like Phalaenopsis and Vandas, is the main stalk where leaves, roots, and flower spikes emerge. Without a healthy stem, your orchid cannot survive. It’s the bulkiest part of the orchid where all life takes place.
The orchid stem is not the same as the flower spike; the later is also called an inflorescence. The stem of the orchid should not turn yellow and is a serious cause of concern. If the flower spike turns yellow then it’s a sign there is something slightly wrong, but not necessarily life threatening for the orchid.
If you were searching for the reasons that your orchid’s stem turned yellow, then this article might not be the right place to be researching your answer. Just so you don’t have to look any further, the reasons that orchid stems yellow are overwatering, too much sunlight, fungal infections, and nutrient deficiency. Each of these need to be treated urgently so your orchid can have a chance at survival.
In this article, I’ll focus only on the reasons why the orchid’s flower spike turned yellow.
None of these reasons are threatening the orchid since the spike will fall off naturally in time. Some of the reasons overlap both with the stem and the flower spike, so take a look at “too much sunlight”, and “nutrient deficiency” which also affect the yellowing of the flower spike.
1. Moisture Stress Causes a Yellow Orchid Spike
To produce a beautiful, blossoming flower spike, the orchid consumes tremendous amounts of energy. Some orchids offer so much energy that after the flower wilts and fades as a normal cycle in their life, they go into dormancy.
Most all Phalaenopsis orchids do not have a dormancy phase, but will keep on blooming and reblooming—after a short pause to recuperate—but not dormancy.
During the production of the flower spike, nutrients have to be constantly flowing through the xylem and up into the orchid buds. To move these nutrients around inside the orchid cells, there needs to be constant and adequate water. Water constitutes a vital part of our lives, and likewise with orchids.
We can have our watering down to a fine art, with the potting medium adequate to our environment and nice healthy roots. Yet if there is not enough humidity in the air, the orchid could sense this difference, resulting in moisture stress, inducing a yellow color.
One sign that your orchid might have moisture stress (as in not enough moisture) is that the aerial roots are shriveled and half dead. They once were bright green when you bought the orchid, but now only brown, paper-like velamen is left over. Velamen is the covering over the actual root that increases the surface area so the orchid can absorb more water.
If the environment is significantly dry, as in 27 to 33% (which the majority of American households are) then it’s more than likely that you’ll need to increase that humidity.
You can use a humidity tray, a mister—which requires tons of manual work, or a humidifier. Each of the selected solutions takes you to an article on Orchideria where you can read why this would or would not be a good choice for you.
No matter what you chose in the end, you need to provide the humidity around the blossom so it can achieve its full blossom. If not, the environment will absorb the orchid’s humidity and pull any extra humidity right out of the orchid.
Since the orchid has already consumed tremendous amounts of energy to produce this spike, it doesn’t have the extra energy to insert more humidity in the spike. The result of this entire process is a yellowing spike that will not produce any orchids blossoms.
2. Dehydration Causes Yellowing Orchid Spikes
The second reason orchid spikes will yellow is not enough water consumption through the potting media. If the aerial roots were shriveling up and dying in the first example, this one will be the actual rots inside the potting media.
Either there is not enough water being supplied, as in quantity, or the frequency needs to be upgraded by a day or two. Under-watering is not only about not providing an adequate amount of water but also not providing the right frequency.
In this case, the orchid is drying out too much before receiving water again. The quantity is fine, but you need to shorten the time your orchid goes without water.
The same reasoning applies to this point as the first one. Orchids use water inside their plant cells to move chemical elements and molecules around inside their plant structures.
To keep the blossom healthy, plump, vigorous, and beautiful, tremendous amounts of water need to be provided to the orchid. After the orchid’s blossoms fall off, you don’t need to provide as much water, since it will be using less. For the orchids which go into dormancy, you hardly need to water at all.
If you notice the spikes on your orchid are turning yellow, check the potting medium to see if it is too dry. Make a note to water more frequently, since the roots will be absorbing a lot more water.
There is another reason that the lack of water might be occurring. If your potting media is moist when you insert your finger into it (the top is always drier than the middle of the pot) then the watering frequency might be spot on. The problem is the lack of roots that can’t absorb this water.
The orchid might not have decent roots, which have probably rotted away from root rot. IF the potting media is constantly damp, this will happen 100% of the time.
I had an orchid that I planted in bark with no sphagnum moss, just as a test. I placed it by the humidifier and left it there 24 hours. Even though I had a fan that circulated, the pot was not ventilated enough. The result was that even though the top bark was drier, the middle of the pot was drenched in sopping wet orchid bark.
The bark never dried.
Phalaenopsis do not take well to being in damp conditions all the time. They like to have a period where their roots can dry out, as if they were back in the rain forest, attached to tree bark. The constant hot winds would quickly dry out their roots after heavy rain. Not all orchids are from tropical and subtropical places, but Phalaenopsis orchids are, and they do not like to be constantly muggy.
3. Yellowing Spikes Caused by Nutrient Deficiency
If your orchid is only receiving rainwater or distilled water and no orchid fertilizer, it will eventually shrivel up and slowly die. Just like we need to live with water but also eat, orchids will need small doses of fertilizer three weeks of the four.
The most common fertilizers have three main ingredients: nitrogen, phosphorous, and potassium, known as the NPK ratio. In this article about the fertilizing method, I explain a lot more detail about those and how to choose the right fertilizer method for your lifestyle.
Yet orchids don’t thrive on just those three elements.
In their natural habitat, they have a gourmet food line with a varying buffet of different chemical elements being provided every time it rains of every wind current that brings floating nutrients.
The main causes of yellowing in orchids (if caused by nutrient deficiency) are lack of potassium, magnesium, zinc, iron, and nitrogen. On the other hand, if you are providing too much phosphorous, then the orchid spike might yellow also.
A good way to determine if the orchid is yellowing because of nutrient deficiency, check the whole plant. It will not be only the orchid spike that yellows, but also the leaves and the stem too. The leaves are the best telltale sign that your orchid has a nutrient deficiency.
Since I am not a botanist, I won’t go into detail about each one, taking a huge risk in talking about what I do not understand. I can give you a small summary of what I have found true for me.
Potassium Deficiency in Orchids- the tips of the leaves will turn yellow as if there is a halo around the edges. The rest of the leaf, as in the middle and where it attaches to the stem are normal green color. To fix this naturally, you can add fruit compost to the top of the media, like a banana peel. Watering with banana water is also a solution.
Nitrogen Deficiency – Not only the tips and exterior edges will yellow, but the center veins also change colors. As if it were a simple color by number painting with only 2 colors, the veins in the center will be yellow but the space in between the veins will remain green. If you’re looking for a chemical safe solution, coffee is a good way to fix this.
Zinc Deficiency – The overall color of the leaf is still green but the spaces in between the major veins are discolored. The veins themselves will still be green. I’ve heard kelp extract is good, but I haven’t tried it personally yet. So, I can’t chime in on that and give my two cents.
Iron Deficiency – Think of iron deficiency as the opposite sign of nitrogen deficiency. In iron deficiency, the orchid will show signs of a yellow leaf entirely, but the veins still remain green. This happens mainly because the pH is either too high (in most cases) or too low.
If you have a lithophyte, an orchid that likes to be attached to rocks, mountain cliffs, or other calcium carbonate-rich environments, the higher pH is a necessity. If you have a Phalaenopsis orchid, an epiphyte, that attaches to tree bark, the pH requirements will be lower, around 5.5 to 6.5. Too high of a pH is the one condition to have an iron deficiency.
If you are not fertilizing adequately the entire orchid will show signs. The one sign of over-addition of elements is phosphorous. If there is too much phosphorus the orchid will yellow as in bright, blinding yellow, bow-tie striking yellow, or 1920’s kitchen paint yellow. I’m not sure exactly how to describe that kind of yellow. It’s not the yellow from too much light, that is pale green. This yellow is the kind that comes in finger paint.
Hold back on the phosphorous and see if the orchid will turn back to the normal green color. This might take a few months since orchids are slow growers.
4. An Extreme Change in Temperature Causes Yellowing Spikes
Once your orchid is in bud and you move it, sometimes a cold draft can come in and shock the spike in formation. This will cause bud blast, as explained in this article.The extreme temperature fluctuation also causes the orchid spike to change colors, ranging from a pale yellow to a dying red.
Orchids bought online during winter also face this problem. Sometimes the travel period is too long and they are exposed to extremely low temperatures will waiting upon arrival. The orchid is not prepared for this change since all it’s known is nursery and greenhouse temperatures that rarely fluctuate year-round.
Since the orchid has no idea how long it will remain in these freezing temperatures, it decides to abort the flowering process altogether and focus on keeping healthy roots and healthy leaves.
It’s not only cold that can make an orchid abort its flowering spike and turn yellow. Heatwaves can do the same thing.
Usually, when referring to indoor growing, this happens because we want to expose our flowering orchid to the world and move it from the grow lights, we had them under, to the living room table or a side table. The central heating unit kicks in and hot, dry air rolls up from the vents and literally puts our orchid in dry sauna conditions.
The orchid spike takes a hit and shrivels up worse than aerial roots do.
To avoid this, keep your orchid in the same place even when it flowers and blossoms. If you absolutely want to change the position on your orchid, then check for currents of either too cold air or too hot air.
The temperature change affects the way the orchid breathes, too. The stomata will remain closed if the temperatures are too hot since it will lose too much humidity during gas exchange. It will prefer to keep the little humidity it has then to open its pores and risk losing more water.
The toxins build up inside the orchid, and some signs are a change in coloration, which leads me to my next point, toxin build-up.
5. Yellowing is Caused by High Toxin Levels
If you are using tap water to water your orchids, then you are providing a lot of elements that your orchid does not need, like chlorine and fluoride. These elements build up over time in your potting medium turning your orchid spike yellow.
If you are using leca pebbles in semi-hydroponics, then this build-up of chemicals is more evident.
The sign that salt build-up or chemical residue is present is a sparkly, crystal-like shine on the top of your potting media. In the case of leca pebbles, it’s easy to spot because the chemicals are naturally driven to the top of the potting media by natural suction in the surface of the pebbles.
If your potting media is bark, then this process will take longer to notice, becoming more threatening for your orchid.
Tap water isn’t the only way that salt build-up occurs. It can also form with too much fertilizer. This happened to me. I got addicted to a fertilization frenzy and week after week started testing fertilizer methods on my guinea-pig orchids.
Needless to say, they didn’t take it well.
Orchids are plants of habits and routines. They did not like the constant changes and yellowing orchid spikes was the first of many issues that my orchids faced.
To fix both these problems, choose an alternate watering method. In this article, I explained the differences between the main water sources methods and how you can choose wisely. For fertilization, reduce the doses and remain faithful to one method of fertilizing.
There is nothing wrong with an occasional bi-yearly dose of extra fertilizer, but don’t change methods and products every week.
6. Ethylene Gas in the Environment
One of the culprits that turn orchids yellow (spikes, leaves, stems, and all) that we never think of is in what we breathe. Most modern-day houses do not have this problem, but some houses occasionally have a spike in the quantities of ethylene gas.
This gas is used in heating and maintains the furnace nice and cozy when it’s cold outside. If the gas pipe has a torn, broken, or damaged part, the ethylene slips into the environment. Since it is odorless and not visible, there is no way of knowing.
If you have a tomato plant indoors, the curling and dying of leaves will be the first signs. Tomatoes are the first plants to show signs of high ethylene presence and in only 24 hours the leaves wilt.
Since orchids are slow growers, the yellowing starts only after prolonged exposure to ethylene.
Needless to say, if your orchid spike yellows because of ethylene, then you might check your overall health too. Headaches, waves of nausea, feeling week, or overtired may be a few signs of prolonged exposure.
I have no idea how to go about fixing this problem, but I will recommend a page written by Michigan State University on ethylene gas and plants and their recommendations to finding the problem and dealing with it. (Source) It does not talk about orchids specifically, but it does give an overall idea of what is happening to your plants. Anyway, I found it interesting.
7. Orchid Spikes Yellow after the Blooming Cycle
This reason, of all the other six mentioned in this article, is the least concerning. Orchids have a natural life cycle and fading flowers, wilting blooms, and the drying back of the orchid spike that turns yellow then brown is a normal part of the orchid’s life.
The flower spike has served its purpose and is no longer needed by the orchid. It takes tremendous amounts of energy to produce that spike and keep it green. To recuperate some of the energy, the orchid makes a point to shrivel the spike, reabsorbing a small portion of that energy back into the plant.
If your orchid is not doing so well in terms of leaves, stems, roots, and overall health, it might be a good idea to cut the stem off prematurely and let the orchid rest quicker.
The yellowing is an indication that the orchid is reabsorbing energy and no longer will need that spike. If you leave the spike on, the orchid might find that it can offer up enough energy to produce another bloom. In this case, the flower spike will start to develop another side spike from a node on the existing spike.
This is why it’s a good idea to leave the flower spike on the orchid—it might just bloom again.
If it doesn’t then the orchid spike will continue yellowing until the orchid spike shrivels up entirely. At this point, you can cut the old brown spike off, by snipping it an inch (2.5 cm) above the node closest to the stem.
In all, I hope it’s the last reason that your orchid spike is turning yellow. All the other six reasons need some action required on your part. Even though they aren’t going to harm the orchid, if the cause is not fixed, then the next problem could be a yellowing orchid stem. In that case, the problem is extremely hard to recuperate.
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