The leaves of orchids (and all sorts of plants) may turn yellow for various reasons.
These reasons range from normal aging to change of seasons to bacterial or viral infection and pest infestation.
This article discusses some of the causes of yellowing leaves (chlorosis) in orchids and offers sound tips and advice for dealing with this phenomenon.
11 Reasons & Solutions For Orchid Chlorosis
1. You Can’t Go Wrong With Bright, Indirect Sunlight
Orchids of all sorts need ample light to produce chlorophyll, conduct photosynthesis, and maintain green leaves.
Just remember that in the wild, most orchids grow in trees. They get light filtered through the tree’s leaves, so they are not prepared for direct sunlight.
Most orchids like Phalaenopsis (moth orchids) – will do very well in a consistently warm room and receive bright, indirect sunlight.
If your only choice is a window that receives bright, direct sunlight, put a sheer curtain in place to provide some protection.
If you do not have an area that receives enough natural sunlight, add a grow light to keep your orchid happy. [source]
2. Time Of Year
When the seasons change, the plants’ culture will also change.
Fluctuations in temperature, light, and humidity can be stressful, and stress will cause yellowing leaves.
However, this is not a cause for alarm. Just correct the cultural environment as well as you can.
Remove yellow leaves as needed using a clean, very sharp implement.
3. Natural Aging
If your orchid is otherwise healthy, but a lower leaf begins to yellow, the leaf is approaching the end of its life span.
Just prune it off with a very sharp, clean implement, and don’t worry about it.
Changes in temperature, light, and humidity can cause stress, which causes yellowing leaves. Excessive repotting, or infrequent repotting, can also cause stress.
Generally speaking, you shouldn’t need to repot a healthy orchid more often than once every couple of years. However, as with most plants, springtime is the best time for repotting.
5. Culture Imbalance
For optimum performance, orchids need the right combination of water, light, and temperature. Too much or too little of these cultural components can cause stress and yellowed leaves.
Generally speaking, orchids like soak and dry watering, bright indirect sunlight, and temperatures ranging from 60° to 75° degrees Fahrenheit.
If you do not water your orchid enough, it will shrivel, and its leaves will turn yellow. It may even appear dead, but don’t give up hope.
Instead, give it a good watering. Keep the plant watered and wait patiently. It may take quite a while to recover, but it may pull out.
When you overwater your orchid, you drown the roots. This will cause leaf growth to slow down and eventually stop. It can also cause the yellowing of leaves.
You should remove your orchid from its growing medium and prune off any soft roots if this happens.
Black and brown roots should also be removed. Leave healthy green roots in place.
Allow your orchid to air for a few days, and then repot it in fresh, airy, well-draining substrate intended for use with the type of orchid you have.
8. Wrong Temperature For Orchid Type
Some orchids are termed “cool temperature” orchids. These are :
These prefer temperatures ranging from 60° to 70° degrees Fahrenheit.
However, exposure to higher temps can cause these orchids to experience stress and yellow leaves.
9. Incorrect Feeding
Overfeeding your orchid can cause burned roots and stress, which lead to yellowed leaves.
Even so, you don’t want your orchid to go hungry, so you must provide just the right amount of nourishment.
Be sure to purchase a fertilizer that is formulated for use with orchids.
It should not be heavy on magnesium and nitrogen because these nutrients will prevent your orchid from being able to absorb iron.
Read the packaging directions carefully, and then provide your orchid with a half dose. If this seems the right amount for your orchid, continue with this dosage monthly.
If you notice that the leaves are developing yellow patches in the center, which then spread, it means your orchid needs a bit more fertilizer.
10. Wrong Levels Of Humidity
Excessive heat and humidity lead to fungal growth. This will cause leaves to yellow and fall, eventually killing your orchids.
Generally speaking, most orchids need humidity levels ranging from 40 to 70% percent.
However, it’s wise to read up on the type of orchid you have to determine what humidity level is best for it.
You can keep humidity levels correct and consistent by using a humidifier with a sensor that turns the device off and on as needed.
If you don’t have this, you might try using a pebble tray under your orchid to help keep the air surrounding the plant naturally humidified.
If your orchid’s leaves begin yellowing at the tip, and then the yellowing spreads over the leaf, suspect a bacterial or fungal infection.
Both fungus and bacteria are more likely to thrive when humidity levels and temperature are too high.
When this happens, correct your cultural circumstances and repot your orchid.
Follow these steps:
- When you take it out of its potting medium, examine the roots carefully.
- Trim away any damaged or rotted roots with a very sharp, sterile implement.
- Prune away affected leaves.
- Rinse the plant thoroughly.
- You may also wish to give the roots a spray with a 50-50 mixture of hydrogen peroxide and water.
- Allow the plant to air for several days and then repot it in a brand new or thoroughly sterilized container with an entirely fresh, new potting medium.
Refer to the tips presented above to care for your orchid as it recovers.