Why are Orchid Leaves Turning Yellow?
Leaves turning yellow on your orchid may not always be a sign of something troubling. Sometimes, your orchid’s leaves are turning yellow because of old foliage, but other times, yellow leaves may be the sign of a disease.
A trained eye will easily tell the difference, but inexperienced gardeners may have trouble telling what’s what. Below, I cover the most frequent causes of yellow leaves in orchids and give you simple and actionable tips on how to fix these issues.
Why are Your Orchid’s Leaves Turning Yellow?
As I mentioned, yellowing leaves at the base of your orchid plant will usually be a sign that old leaves are naturally dying back, and it’s nothing to be concerned about.
However, if yellow leaves are all over the plant, or yellowing is something that happens frequently, you may want to give a read to the possible reasons below to see if any of these match what you’re experiencing with your orchid.
Here are the most common reasons for orchid leaves turning yellow:
- extreme temperatures
- too much direct sunlight
- excess watering & water quality issues
- deficiencies & fertilizing issues
- fungal or bacterial infections
Let’s see each cause in more detail:
Exposure to Extreme Temperatures
One of the reasons why phalaenopsis orchids are excellent houseplants is that they thrive in the temperature range most of us can offer them indoors.
Orchids will accept temperatures that are between 60 and 80 °F. Prolonged exposure to temperatures outside this range, will surely bring about a host of issues including yellowing leaves.
If temperature drops below 60 F regularly in the room where you keep your orchids, or they’re located in a windowsill without good isolation, leaves will progressively yellow, then turn brown or black, and they will eventually drop.
On the other end of the spectrum, constantly exposing your orchid to temperatures above 80 F will overburden the metabolic processes of the plant and cause yellowing leaves, which will progress further if the temperature is not adjusted.
As tropical plants, orchids enjoy moderate temperatures and a humid environment, where the difference between nighttime and daytime temperatures is modest.
If temperatures in your home fluctuate too much during winter, you should invest in a thermometer that will help you keep track of seasonal temperature changes that might influence the health status of your orchids.
Too Much Direct Sunlight
Phalaenopsis orchids rarely receive strong direct sunlight under the canopy of trees in their natural habitat. Indoors, they thrive in bright indirect sunlight.
If your orchid is kept in a windowsill exposure to strong direct sunlight, leaf damage is inevitable. Whether it’s yellow leaves or downright scorched leaves, move your plant to a north or east-facing window instead to avoid any further damage.
In winter, when strong sunshine is scarce, you can move your plants back to a south-facing window, but in the summer, you should avoid keeping orchids in bright direct light.
Excessive direct sun exposure will cause browning leaf tips and can even damage the roots of the orchid, leading to the eventual demise of the plant if the issue is not corrected.
Excess Water & Water Quality Issues
Overwatering is a common threat to all houseplants. Inexperienced gardeners have a tendency to overwater plants out of a desire to nurture and care for their plants.
Understanding the water requirements of orchids will help put things into perspective, and you’ll know how much and when to water them. Overwatering is one of the chief reasons for yellowing leaves.
For starters, it’s important to remember that phalaenopsis orchids are tropical plants that need quite a bit of humidity and are epiphytes, meaning they grow on host plants, which allows roots to get quite a bit of aeration.
This also means that their roots are not accustomed with excess water as any rainfall, however heavy will quickly drain from the plant’s growing medium.
Therefore, one of the first steps in preventing overwatering is picking out the right growing medium for these plants. Soil with a high water holding capacity should not be considered.
Commercially available orchid potting media are usually a combination of tree bark chips (redwood, ground fir, Monterey pine, etc.), sphagnum moss, charcoal, coconut husk chips, and perlite.
Potting media designed specifically for orchids will drain fast and won’t allow any excess water to stick around the roots and cause root rot.
And it goes without saying that proper drainage holes on the orchid’s container are indispensable to allow the water to escape and the roots and soil to ventilate.
Of course, the next step in preventing overwatering is knowing when to water your orchid so that you don’t do it too frequently.
A quick and easy rule is to poke your finger into the potting medium and check for moisture or dryness. If the soil is dry and roots are starting to have a silvery color, it’s high time you watered your orchid. If the soil is moist, check again in a few days.
Alternatively, you can use a wooden skewer to check the soil and follow the same principle — if it’s dry, water your orchid, if it’s wet, check again in a few days.
Slightly underwatering your orchid is always better than overwatering, so it’s best to err on the side of caution.
Another water-related cause that may be turning your orchid’s leaves yellow is related to the quality of the water. If you’re using tap water to water your orchid and the water is too hard (i.e. high in dissolved minerals like calcium and magnesium), it can cause a number of deficiencies and turn your leaves yellow.
On top of this, tap water will usually contain chemical disinfectants like chlorine or chloramine, both of which can cause orchids to develop yellow leaf tips or yellow leaves.
Leave your tap water to aerate overnight so that chemical disinfectants can evaporate, and only then water your orchids.
Nutrient Deficiencies & Fertilizing Issues
Overfertilizing is another common issue that may cause the leaves to turn yellow. Light fertilizing with a diluted houseplant fertilizer (½ or ¼ strength) or orchid fertilizer is all these plants need.
I only fertilize during the growing season every 2 weeks and stop feeding when my orchids are in bloom.
The opposite can also happen — your orchid may also suffer from deficiencies that can also manifest as yellow leaves.
Despite the potting medium containing some nutrients, with time these will be used up and your orchid will show signs of nutritional deficiency.
Lack of iron, manganese, nitrogen, zinc can all explain why your plant’s leaves are losing their vibrant green color and fade into yellow. Picking a suitable fertilizer will help solve the issue.
Fungal & Bacterial Infections
While fungal, viral or bacterial infections will cause yellowish spots, sometimes entire leaves can turn yellow.
The most common fungal infection to affect orchids is root rot, which as you may know already is caused by overwatering your plant.
In the incipient phase of the disease, you may still save the plant. Take the plant out of its pot, clear the roots of diseased or rotting roots (brown, black and soft mushy roots should be removed) and salvage any firm, healthy roots.
You can replant the orchid in a fast-draining potting medium and hold off the water for a week to see if the plant will bounce back.
The two other diseases that can affect your orchid include fungal leaf spot and bacterial brown spot. Bactericide sprays or fungicide sprays coupled with removing diseased leaves can help solve the problem.
A perfectly normal reason for your orchid to have a leaf turn yellow is old foliage being replaced with new growth, so that the plant will prioritize new growths as seal off old leaves, which will turn yellow.
While it’s not a beautiful sight to have one or two yellow leaves at the base of the plant, I usually don’t remove them until I’m certain they’ve withered away, because removing them too soon may increase the risk of infection to the plant.
When I do decide to remove them, I use a sharp and sterile knife to remove the leaf.
A further issue that can turn your orchid’s leaves yellow is a sudden change in the environment of your orchid. Usually, yellowing leaves will be accompanied by leaves or blooms that drop from the plant.
Sudden changes in the plant’s environment include moving the plant from one location to another within your home, taking your plant outdoors or back indoors, or simply bringing your plant home from the store.
Your orchid will usually adapt to the new location if the parameters are within their acceptable range. Keep an eye on the plant’s evolution to see if you need to make any adjustments.
As you can see, there are a few reasons why your orchid’s leaves may be turning yellow. It’s important to carefully assess the situation and make a correct diagnosis before you can apply any remedy.
Sometimes, the cause is something simple that you can easily remedy, other times you may be dealing with a disease that should be treated without delay.