Hoya is a large genus comprising over 500 species. Each species of wax plant, as hoya is commonly called, can have slightly different requirements. Hoyas, in general, may not be the easiest houseplants to care for. And their needs can manifest in the form of leaves turning yellow.
If a single leave starts to turn yellow, it’s not a reason for concern. It’s probably just a natural exchange of old leaves with new ones.
However, if the whole foliage is changing to yellow, you should be on alert. Hoya leaves can turn yellow because of the incorrect amount of light, amount of water, or nutrient deficiencies. Neither pest infestation nor disease is excluded as a possible cause.
There are multiple things you should look for when cultivating hoyas. I carefully chose the 7 most common causes for hoya plant leaves turning yellow, and in this article, we’ll walk through all of them. Let’s dive in!
What Causes Hoya Leaves to Turn Yellow?
There are many factors that can contribute to the yellowing of hoya leaves. And sometimes, it can be a challenge to uncover the real culprit. However, the way the leaves turn yellow or the yellowish patterns they create can tell you more.
Yellowing Patterns can Tell you More
Understanding the patterns in which Hoya leaves turn yellow can provide invaluable clues in your quest to diagnose the underlying issue. Not all instances of yellowing are created equal; sometimes, it’s not just about the color change but also where and how it happens or what other issues it’s accompanied by.
- Yellowing from the Tips: When you notice the tips of your Hoya leaves turning yellow, it often indicates an issue with the plant’s watering habits. This can be a sign of over-fertilization or water with high mineral content.
- Yellowing from the Edges: Yellowing along the edges of the leaves may suggest environmental stress, particularly exposure to cold drafts or abrupt temperature changes.
- Yellowing in the Center: Yellowing in the center of the leaves can point towards a more chronic issue, such as nutrient deficiencies or root-related problems.
- Uniform Yellowing: If the entire leaf turns uniformly yellow, it could be a sign of natural aging. Hoya leaves do have a lifespan, and as they age, they may turn yellow and drop off. This is typically nothing to worry about as long as new growth continues to appear.
- Mottled Yellowing: A mottled pattern of yellowing may be indicative of pests or diseases, such as spider mites or fungal infections.
These rules or patterns are not here for you to strictly follow. Nature is unpredictable, and the individual signs can vary. But you should use them as a guideline to help you uncover the real cause of hoya leaves turning yellow.
While providing your hoya with enough water is essential, excessive watering can cause the leaves to turn yellow.
When you consistently provide your hoya with more water than it needs, the roots become waterlogged, and oxygen deprivation occurs. This lack of oxygen impairs the root’s ability to absorb nutrients, leading to the yellowing of leaves.
Additionally, excess moisture can also create a welcoming environment for root rot and other fungal issues that further contribute to leaf discoloration and further impair your plant’s health.
Usually, its a lot better to underwater than overwater your plants. This also applies to wax plants, although underwatering can also lead to yellowing, as you’ll read in a second.
You have one undeniable advantage when growing plants in pots. You can always check the moisture of the soil with your fingers. If you feel that the soil is excessively wet, wait a few extra days before watering again.
What’s “excessively wet”? When you touch the soil with your fingers, it will feel extremely damp, and if you squeeze it, water may be released. And with hoyas, this interpretation can be pushed even further, as hoyas like the soil to be more on the dry side. So if you feel that the soil in the upper 1 inch (2.5 centimeters) is still wet, wait before watering again.
Surprisingly enough, while overwatering can turn the leaves on your hoya yellow, the opposite issue – underwatering – can have a similar effect.
All living organisms need water, and its no different for plants. The lack of moisture affects the plant’s ability to perform crucial functions like nutrient uptake and photosynthesis. As a result, the plant will shift itself into a state of survival. In this state, the plant tries to save as much water as possible, and one effective way to do that is by reducing its leaf functions. Which will manifest in the discoloration of the leaves, apart from other issues.
If the soil is dry to bone and you know you haven’t watered your hoya in a few days, give it a drink.
3. Lighting Issues
Hoyas are tropical plants that live under the canopy of trees. They adapted for subtle, diffused light. And if you don’t meet to that standard, the leaves can turn yellow.
That’s because insufficient light can lead to decreased chlorophyll production, the green pigment that makes the leaves naturally green. That can result in pale or yellowing leaves.
On the other hand, too much direct sunlight isn’t ideal either. Direct sunlight can scorch the leaves and cause them to turn yellow and ultimately brown and drop off.
To maintain the health and vibrancy of your hoya, it’s crucial to provide the right amount of light. Start by choosing the right spot to place your hoya in. The pot should be placed somewhere where the plant will be able to get indirect light all day long. Usually, an east or south-facing window is ideal.
4. Pest Infestation or Diseases
These hardy plants are not immune to unwanted visitors like spider mites, mealybugs, or aphids, which can feast on their foliage, causing damage and discoloration.
As with all other causes, pests or fungi can affect the overall health of your hoya. As the plant is not able to perform all the processes as before, whether that’s related to photosynthesis, water, and nutrient uptake, or simply these bugs steal sap from the stem, it will manifest as yellowing leaves.
Pest infestation or diseases are easier to differentiate from other causes, as you’ll be able to see other signs. For instance, as mealybugs feed on the sap, they leave a sticky, sugary residue known as honeydew behind, which can be observed as white spots on your hoya leaves.
Pests and fungi can spread very fast, so early detection and prompt action are crucial. I always encourage gardeners not to be afraid of reaching for insecticide or fungicide as soon as possible.
Of course, pesticides won’t solve the yellowing of the leaves if the underlying issue is not solved. If you created a breeding ground for pests because of high humidity, overwatering, and low air circulation, using pesticides is just a temporary solution.
5. Temperature Stress or Draft
As tropical plants, hoyas don’t like cold. Even sudden, small fluctuations in temperature can cause distress, causing the leaves to turn yellow.
Hoyas thrive in stable and moderate temperatures between 68 and 85 degrees F (20 to 30 degrees C). Lower temperatures than that can be tolerated, however, below 60°F (15°C) is simply too cold.
A draft can also have the same effect as prolonged cold temperatures. While the draft won’t kill your plant or trigger the yellowing of hoya leaves immediately, it still causes a high level of distress. This can also slow down the hoya growth rate significantly.
6. Nutrient Deficiencies
Actually, many varieties from the hoya family are considered succulents. But unlike many succulents, hoyas need a balanced supply of essential nutrients.
Fertilizing your hoya regularly with a balanced fertilizer specially made for them won’t hurt anything. Alternatively, you can get a soil testing kit and target only the actual deficiencies.
The second approach can improve your plant’s health tremendously. But it’s also very easy to overfertilize your hoya and cause more harm. So I would recommend sticking with a fertilizer mix made for hoyas.
Additionally, when you fertilize your hoya, do that only in the peak growing season, during spring or summer. In the winter, the plant goes partially dormant.
7. Low Humidity or Bad Air Circulation
With hoyas, it’s especially important to strike a balance in terms of humidity. Hoyas are tropical plants that are used to very high humidity levels. However, high humidity can also be an invitation for pests and diseases.
That’s why you need to balance it out with good air circulation around your plant. Make sure not to place it too close to walls or other objects. You can even move the air in your apparent a bit with a fan, not directly blowing on your plant, of course.
8. Natural Foliage Turnover
And lastly, let’s not forget that the leaves of your hoya have their own lifespan.
As the leaves age, they may turn yellow before eventually dropping off. These leaves will be later replaced by new ones. This process is entirely normal and shouldn’t raise alarm unless excessive yellowing occurs throughout the entire plant.
Can you Save Yellow Hoya Leaves?
Unfortunately, you can’t generally reverse the yellowing of already affected hoya leaves. But you can take steps to prevent further damage and promote the health of your plant.
But there’s one case in which hoya leaves can regain their green hue. If the issue that caused the yellowing of the leaves is related to nutrient deficiency, after the plant gets all the nutrients and minerals it needs, the leaves may come back green.
But yellow leaves caused by overwatering and underwatering or inadequate sunlight can’t be reversed. In case of water issues, the leaves are likely already partially dead and will wilt soon. In the second case, when the plant didn’t receive enough sunlight, it already lost chlorophyll which can’t be restored.
How to Never See Yellow Hoya Leaves Ever Again
When it comes to the health of your hoya, prevention is key, and proactive care is your greatest ally.
Your goal should be to mimic its natural habitat as closely as you can. Of course, it’s not possible to turn your apartment into a tropical jungle, but you can make it closer to that goal.
Give your hoya a nice place with plenty of sunlight all day long. The sunlight should be filtered, as direct sun could scorch the leaves.
Make sure to water your plant when it truly needs to be watered. Simply use a “finger test” to check whether or not the top inch of the soil (2.5 centimeters) is dry or still wet.
And with that, you may never see yellow leaves on your hoya again.
Before you go…
I am sure that one of the reasons you got hoya was their beautiful flowers. Hoyas are known to be very slow growers. So now that you solved leaves on your hoya turning yellow, is time to give it a bit of headstart in growing. Read my next article to check all the other things that hoyas need for faster growth…