Hoya Leaves Turning Yellow – Reasons and Remedies
Hoya leaves turning yellow should be a cause for alarm, and immediate action is needed. Hoya is a genus comprising 200 to 300 plant species native to tropical and subtropical Asia and Oceania. The most cultivated indoor species is ‘Hoya carnosa’. It is also called the ‘Wax plant’ due to its thick waxy green leaves. This classic plant lives long, grow extensively, and forms beautiful porcelain-like fragrant flower clusters. Also, Hoya carnosa is a favorite indoor house plant because it has scented flowers and alluring folia.
However, Hoya leaves can turn yellow due to overwatering and poor draining potting medium. The leaves could also yellow due to nutrient deficiency, temperature stress, aging, acclimation, improper lighting, pests, and diseases. Luckily, when you get to the root cause of the yellowing, you can always fix the problem. Read on; this article will discuss the causes of yellow leaves and remedies:
What Causes Hoya Leaves to Turn Yellow?
Overwatering is a significant cause of Hoya leaves yellowing. When you give excess water to the plant, the soil aeration reduces. Your plants’ roots require enough oxygen to supply nutrients to the whole plant.
With excessive watering, the roots are suffocated and do not function properly. The leaves do not get enough nutrients required for photosynthesis. This deficiency leads to yellowing, with the older leaves getting affected first.
Too much water could result from frequent watering, a pot without drainage holes, or poorly draining soil mix. To avoid excessive watering, constantly water the plants when the top 2-3 inches of the soil is dry.
Check for drainage holes in your pots and blocked holes that could mean the excess water is not getting out. You can fix these hole issues by changing your Hoya into new pots with proper drainage. Similarly, you can unblock holes by poking with a sharp sterilizing tool.
- Improper Potting Soil/Mix
In their natural habitats, Hoya’s roots grow into the crevices of trees and not in the soil. Therefore, the potting media you choose for your indoor Hoyas should be well-drained and aerated.
A poorly drained soil mixture could cause too much water in your pots. If the soil holds water for too long, the roots are not aerated and will rot. Damaged roots mean the plants will begin to yellow. A watering schedule will not help solve the overwatering issue.
If you notice that your soil mix is still very wet even after days of not watering, then you have a problem. You need to re-pot your Hoyas instantly into new pots with a suitable medium.
You can choose a potting mix of equal parts of cactus, orchid, and perlite mix. The resultant soil mix would be highly recommended as it is a quick-draining mix.
There is another pot mix you can use for your Hoya plants, including two parts of peat moss and one part of pumice. It also makes an excellent mix for Hoyas.
- Temperature Issues
Hoyas have a tropical origin and hence tolerate high temperatures better than they do in cold weather. The optimum temperature for indoor Hoya plants is 65 to 80 degrees Fahrenheit. However, the plants can tolerate up to 90 degrees F during hot weather and only 50F in cold drafts.
In cold drafts, your Hoya leaves will yellow and eventually dry out and fall off. Although the plants can withstand high temperatures, the high heat with low humidity will also cause yellowing. When it gets too hot, an issue of underwatering leads to yellow leaves with brown tips and edges.
Temperature issues occur due to seasonal change. Be sure to check your plants when there is a change in the weather. Keep a thermometer near the plants to track temperatures. Adjust the plants’ environment according.
Do not place your Hoyas near an air conditioner during the cold weather. In addition, keep your pots away from open windows that could draft in cold temperatures.
- Under watering
Water is essential for any plant growth. It provides a medium for the transportation of nutrients from the roots to the rest of the plants. Therefore, when you give your plants too little or no water, the plants will start wilting and yellowing leaves.
Hoya plants are epiphytes with thick leaves that are succulent-like and can withstand dry periods. However, these do not last long, and too little water will eventually cause the yellowing of the leaves.
Underwatering might not be the significant issue causing yellowing to your Hoya leaves. However, if the potting mix feels very dry, water deficiency is the cause of the yellow leaves.
Check the top 2-3 inches of the soil to feel whether it is too dry. If the medium is dried, it is time to water and revive your plants.
- Nutrient Deficiency
Hoyas are heavy foliage plants and require enough nutrients to thrive. The most common nutrient deficiency that leaves yellowing is nitrogen, followed by potassium. Other micronutrients that could cause yellowing in your plants are phosphorous and magnesium.
The leaves require nitrogen for photosynthesis to produce chlorophyll. Chlorophyll is the green coloring matter in leaves. When your plants lack these nutrients, the leaves will yellow, starting from the older leaves to the newer ones.
You can differentiate leaves yellowing due to nutrient deficiency from other causes by observing young leaves that tend to be pale green and wrinkled.
While the yellow leaves may not recover from insufficient nutrients, the newer leaves emerge healthy. Most Hoya pot mixes will supply enough nutrients to your plants in the first to the second year. However, you must add fertilizer every four to six months after two years.
There are specific fertilizers with all the micronutrients needed for Hoya plants that you could use. However, you can also use standard fertilizer in half-strength to supplement your soil mix.
- Old Leaves
Aging is a natural and inevitable process in plants’ life. When your plants are old, they will shed off the old leaves to give room for the growth of newer leaves. Old leaves tend to yellow, dry out then fall off from the plants. Yellowing should not be a problem when you have ruled out all the other possible causes of yellow leaves.
You can eliminate older leaves by pruning using sterile tools to allow the plants to concentrate on producing newer leaves. Similarly, you can wait until the plants shed off the leaves naturally.
Hoya plants are relatively resistant to pests. However, some sap-sucking insects can infest your plants in some conditions. The most common pests that affect the Hoya plants are aphids and meal bugs. Other pests that could also infest your plants are spider mites, thrips, and scales.
These pests damage the leaves by piercing and sucking sap from the plants. You will notice a change in leaf pattern due to piercing marks and yellowing of the leaves.
Pests can cause more harm to your plants if left uncontrolled. Make a routine to scout and check the leaves’ upper and lower sides and along the stems. Aphids, for instance, will infest the more downside of leaves in colonies. You will notice black soot from these insects.
The first step is to examine the magnitude of the insects. If only a small number of insects, you can isolate the affected plant and wash off the pests using soap water.
You can use insecticidal sprays for the specific insects on your plants for heavy infestations. When you realize your Hoya plant is badly damaged, discard it by burning or burying it deep in the soil.
Hoyas are reasonably resistant to diseases due to the waxy nature of leaves that offer protection. However, under poor growing conditions such as saturated soils, Hoya plants are vulnerable to infections.
Some diseases affecting Hoya plants can cause yellow leaves. The most common condition of Hoya that causes leaves to be yellow is root rot.
Root rot mainly occurs due to overly wet soils that encourage the growth of fungal microorganisms. The roots turn brown/black due to suffocation, which leads to poor transport of nutrients to the leaves. You only notice the yellowing of leaves at the advanced stages of the disease.
You must uproot the plants and check the underground parts for root rot disease. If the roots are not severely damaged, then trim with sterile scissors and re-pot the plant in the new soil mix. For heavily diseased roots, it is time to get rid of them before infecting other plants.
- Acclimation to New Environment
When you often decide to have Hoya houseplants, you source them from nursery propagators. There is the likelihood that the environment is different, plus the transportation part.
So, your plants will be trying to adapt to a new environment. It is common for plants to shed off some old leaves as they adjust to a different environment. Before the leaves fall off, you will notice yellowing.
When you provide your Hoya plants with the proper conditions, relax and allow the natural process to occur. The plants will eventually regain from shock and grow into healthy plants.
- Too Much or Too Little Light
Hoyas naturally grow in the tropics in association with trees and other plants. The plants are said to be gap plants because they take advantage of the gaps left between trees to access sunlight.
Thus, the ideal lighting for your Hoya plants would be the bright but indirect sun. Excessive or low lighting can cause your leaves to be yellow.
• Too much light
Although plants require light to produce chlorophyll, excessive lighting will develop yellowish or brownish color on leaves. When you provide too much light, the plants stop processing more chloroplasts in which the chlorophyll is formed. The leaves begin to fade and yellow with extended hours in direct sunlight. Too much light could lead to brown tips and edges.
• Too little light
Contrary to excessive lighting, the plants adjust to produce more chlorophyll in low lighting. Initially, your plants will become greener as it tries to grasp enough light. However, after a short period, the Hoya will not be able to sustain itself in the low light, thus turning yellow. The older leaves will be affected first, going on to the young leaves.
Low lighting means less photosynthesis hence less growth and yellowing of leaves. Furthermore, in poor lighting, the water in your pots tends to dry slowly. Water retained for long could also lead to yellowing of leaves due to waterlogging.
Always place your plants in well-light areas away from direct sunlight to avoid yellowing due to lighting issues. You can try to put the Hoyas near east or west-facing windows for optimal lighting. Depending on the Hoya variety, you can try artificial lighting in darker areas for a few hours.
How To Save Yellow Hoya Leaves
There is only one way to save your yellow Hoya leaves. It would help if you got the cause of the yellowing and fixed the issue. You can eliminate the reasons mentioned above for yellowing until you arrive at the one concerned.
Unfortunately, yellow leaves will not turn back to green. You can remove them by pruning or being patient as the leaves fall off themselves. Once the issue is resolved, the newly emerging leaves will be healthier, and the yellowing problem will not occur again.
In conclusion, Hoya leaves can turn yellow due to watering issues, lighting and temperature stress, age, acclimation, nutrient deficiency, and pests and diseases. You can revive your plants with proper watering, bright but indirect sunlight, controlled temperatures, and protection from pests and diseases. Then, enjoy the long vining and fragrant flower clusters of your healthy Hoyas.