:strip_icc()/bhg-orchid-with-yellow-leaves-d3f0c06ee4ca4bd0baecaabe8b11be10.jpg?ssl=1 "6 Things That Make Orchid Leaves Turn Yellow, and How to Save Your Plant")
Key Takeaways
- The most common cause of yellow orchid leaves is overwatering.
- Pests, nutrient deficiency, and improper light are also fixable causes for yellowing leaves.
- Yellow leaves may also be just a natural sign of aging and not a problem.
It’s the moment that makes an orchid owner’s heart sink. You walk past your beloved plant and see a sickly yellow leaf. Before you panic, realize that those yellow leaves are your orchid’s way of sending you a signal that something in its environment is not right. The problem is usually fixable. If you know how to play detective and pinpoint the cause of those yellow leaves, you can get your plant back to a healthy, deep green.
Focusing on moth orchids (Phalaenopsis)—the most popular orchids sold as houseplants—here are six common reasons orchid leaves turn yellow and how to fix the problem.
Justin Kondrat is the lead horticulturist for the Smithsonian Gardens Orchid Collection.
1. Overwatering
Too much water is the most common cause of yellowing leaves on a moth orchid, according to Justin Kondrat, lead horticulturist for the Smithsonian Gardens Orchid Collection. “People tend to think water is a love language for plants, and they water an orchid constantly because they think that’s the way to care for it,” Kondrat says.
However, too much water causes an orchid’s roots to rot, and those damaged roots can no longer absorb and transport nutrients and water essential for healthy, green leaves. Instead, the leaves turn yellow and wilt because they can’t get what they need.
How to diagnose: Pick up the pot. If it’s heavy, it’s likely because the potting medium is over-saturated with water. Check the roots. If they’re brown or black instead of green or silvery, you have an overwatered plant.
How to fix: “Orchids need air circulation around their roots,” Kondrat says. That’s why it’s important to let the potting medium dry out between waterings. Generally, moth orchids need water once a week.
How you water matters as much as how much you water, Kondrat says. He advises taking your orchid to a sink and letting water run through the pot and out the drainage hole for seven seconds. This flushes out salts from fertilizers that accumulate, and keeps the roots healthy.
2. Pests
Blotchy yellow spots on leaves may be a sign your orchid has an infestation of mealybugs or scale insects. These bugs suck the plant’s vital sap, weakening the plant and disrupting its ability to produce chlorophyll to feed itself.
How to diagnose: Examine the plant closely to look for signs of an infestation. “Inspect the underside of leaves, especially the ones with yellow blotches,” Kondrat advises. “That’s where these pests are usually found.” Look for insects on new growth, too, because they love to attack tender new shoots and baby leaves.
How to fix: Wipe the leaves clean with a damp cloth, then treat the orchid for pests. Use a cotton swab dipped in isopropyl alcohol (70% solution) to dab on the bugs and remove them from the plant. If the orchid has a major infestation, apply insecticidal soap or neem oil, repeating the treatment every few days until the pests are gone. Typically, 3 to 4 applications will do the trick.
Except for leaves that are infested with a pest, partially yellow leaves should remain on the plant so the orchid keeps photosynthesizing and feeding itself. “Only remove a leaf when it’s mostly dead or yellow and no longer functions as a sort of solar panel producing energy for the plant,” Kondrat says.
3. Nutrient Deficiency
Pale yellow leaves may be a sign that an orchid did not receive proper fertilization, Kondrat says. Understand that fertilizer isn’t food for plants; it’s a sort of multivitamin for them. Yellowing orchid leaves are frequently caused by a lack of magnesium, an essential element for photosynthesis.
How to diagnose: Oldest leaves may look mottled and pale green to yellow.
How to fix: In the spring and summer, Kondrat recommends feeding your orchid weekly with a 10% diluted fertilizer solution every time you water it. Be sure to flush the orchid with water prior to applying fertilizer so you don’t overfeed it.
Taper off on the fertilizer during the fall, and stop fertilizing entirely around Halloween, Kondrat says. Shorter days in winter will send the plant into a natural dormancy, and it won’t need extra nutrients. Kondrat also suggests applying Epsom salt to your yellow-leaved orchid to give it a shot of photosynthesis-boosting magnesium (1.5 teaspoons per quart of water).
4. Light Issues
Both too much light and too little light can cause yellowing leaves on orchids. “Most people tend not to give orchids enough light,” Kondrat says. “They put them too far from a window or bring their orchid into the middle of their house because they want to enjoy the blooms, and then they don’t take it back to the window.”
How to diagnose: Yellow-green leaves may indicate that the orchid is not getting enough light, Kondrat says, while a reddish tint on the leaves means the orchid getting too much light. In direct sunlight, leaves may develop sunscald, which looks like tan, dried out spots.
How to fix: Orchids need 6 to 8 hours a day of bright, indirect light during their growing season and 4 to 6 hours during the winter when they’re dormant. They do not tolerate direct light.
If your orchid is blooming and you want to move it to a less bright location to admire the flowers, Kondrat doing so for just a week at a time, then taking it back to its brighter spot for the next week. “Some of these moth orchid blooms can last for months,” he says. “Having an on/off week is a good way to make sure you are giving it enough light when it is blooming. When it’s not in bloom, park it in front of a window and let it recharge,” he says.
If your orchid needs less light, place it in front of a window where it gets bright, indirect light. If you don’t have sufficient natural light from a window with sufficient, Kondrat suggests using grow lights.
5. Wrong Potting Mix
A regular houseplant potting mix holds too much water for orchids, causing root rot, which then leads to yellow leaves. Even sphagnum moss often used for orchids can hold too much moisture as well as soluble salts from fertilizers that need to be rinsed out each time you water.
How to diagnose: Yellowing, limp leaves and black, mushy roots indicate overwatering.
How to fix: “I recommend a chunky, bark-based media as opposed to pure sphagnum moss,” Kondrat says. Bark mixes drain quickly and keep orchid roots moist but not soggy. “If your house has dry air, put a little sphagnum moss in the bark mix, maybe a 5% ratio, to give the roots a little more moisture,” Kondrat recommends.
6. Natural Aging
Leaves have a natural lifespan. Sometimes a yellowed leaf isn’t a sign you’ve done anything wrong; it’s just the plant aging normally. Your healthy orchid will grow new leaves to take its place.
How to diagnose: If the yellowing occurs on the older, lower leaves of an orchid, and there are no signs of pests or overwatering, it’s probably part of the orchid’s natural aging process, according to Kondrat.
How to fix: Leave the yellowing leaf on the plant until it turns the color of a ripe banana peel. “At that point, trim it off; it won’t green up again,” Kondrat says. “It can no longer make food for the plant, and removing it will not harm the orchid.”