Hoyas are popular houseplants, grown for their attractive flowers and leaves. And like most plants, hoya leaves can sometimes turn brown/yellow or start to wilt.
Yellow, brown, wilting, or falling hoya leaves are often the result of water stress, particularly overwatering. New plant owners are known to overcompensate in the area of watering. Still, factors like temperature, light, soil drainage, pest, and diseases may also be responsible.
However, if you would like detailed explanations of the possible causes of yellow, wilted, or falling or Hoya leaves, you will find that this article does just that. Additionally, the article proffers preventive measures and solutions to these problems.
Hoya Plant Species
Otherwise known as wax or porcelain plant, Hoya is a genus with 200 to 300 species of tropical flowering plants. The leaves of the more popular hoya plants are thick, green, and glossy, which is why accounts for the nickname. Some commonly grown species include:
- Hoya Carnosa Compacta
- Hoya Carnosa Variegata
- Hoya Australis
- Hoya Obovata
- Hoya Kerrii
Hoya Leaves Turning Yellow
Occasionally, you may observe that the leaves on your hoya plant begin to turn yellow and this could be due to several factors including;
- Incorrect watering
- Inadequate sunlight
- Cold drafts
- Nutrient deficiency
- Pests and diseases
Over-watering or under watering the plants will cause it to have yellow leaves:
While hoyas are generally hardy plants and can endure some neglect, extended periods without water will cause the leaves to turn yellow and eventually drop as the plant tries to conserve its scarce water resources.
As the name suggests, overwatering is when the plant is given too much water such that the potting soil remains moist for too long, causing the plant roots to rot.
Plants get water from the soil by their roots using capillary action and the xylem tissue. Accordingly, rotted roots cannot take up water from the soil to the plant. Thus, it becomes a case of underwatering brought on by too much water.
Needless to say, the remedy to under watering is to water the plant more frequently. However, frequent watering might, in turn, lead to overwatering. Hoya plants do not require much water compared to other houseplants like the umbrella palm, as their thick leaves can retain moisture, thus making them somewhat drought resistant.
Watering Hoya plants can be a tricky business. There is no single watering schedule that is perfect or works in all cases. The water needs of even plants of the same species will vary depending on prevailing conditions like seasonal, temperature, and humidity.
In hotter temperatures, increased evaporation from the soil and the leaves of the plant (transpiration) leads to greater demand for water. A similar plant in cooler temperature will require less water, as evapotranspiration losses are minimal.
Furthermore, plants in humid environments do not require as much water as those in drier climates, and in the winter, plants need even less water, as there is little growth in the cold weather.
An effective watering schedule that ensures that the plant gets the right amount of water is to water only when the soil is almost dry by flooding the soil with water until it is fully saturated.
Poorly Drained Soils
Overwatering might not always be a result of too much water applied to the plant. It could result from a poorly drained soil that retains water or a container with blocked or absent drain holes. Either of these will cause water to remain in the soil for too long, causing the roots to rot.
The benefits of moderate watering will be canceled if the soil is too dense to allow water to pass through or the holes in the container are blocked or absent.
Regarding soil, hoya plants are natural epiphytes, meaning that in the wild they do not grow in soil, but instead attach their roots to other trees and derive moisture and nutrients from the air. Consequently, potting soil for hoya plants should be quick draining and well aerated to allow the speedy passage of air and water.
A mixture of equal parts, perlite, and regular potting soil is quick draining and well aerated enough. Furthermore, it is advised to repot hoya plants after two or three years, as given time, the soil will get compacted and water will not pass through as quickly as before and may cause problems to the plant’s root system.
Rarely do pots not have holes, but the openings can sometimes get blocked, as some hoya species are fast growers, and their roots may grow to block out the drain holes on the pot, thus preventing water from flowing out. In such a case, you will need to transfer the plant to a new container as the plant has outgrown its current housing, and continued stay will have negative effects on the plant.
Rotten roots can not be salvaged, if root rot is the cause of the yellowed leaves, then the plant will need to be removed from the container and the rotten roots cut off before the rot spreads to the entire root system.
Chlorophyll is the green pigment in plants that give the leaves their color. Chlorophyll also converts sunlight into chemical energy needed for various plant processes.
Chlorophyll production is dependent on the plant’s conversion of light energy to chemical energy through photosynthesis. As such, in the absence of light, plants cannot produce more chlorophyll, and the affected leaves will eventually fade.
The obvious remedy to inadequate lighting will be to expose the plant to bright light. However, not just any type of sunlight will work, as Hoyas are tropical plants and do not enjoy direct sunlight. Position the plant next to the west or east-facing windows as this will deliver ample sunlight while sparing the plant the sun’s harshest rays.
You can tell when yellowing is caused by insufficient light when the leaves are yellow only on the side that faces away from the window or light source, as opposed to an even distribution of yellow leaves.
As such, rotate the plant often so that all sides get some time in the sun. In dark areas or where there are no windows, you may also meet lighting requirements by using a full spectrum fluorescent grow lights.
Hoyas and other tropical houseplants do not enjoy cold drafts and sudden drops in temperature. They may show their displeasure at the cold with yellowed leaves. Furthermore, continued exposure to cold temperatures will cause the yellowed leaves to dry out completely.
Thus, take plants away from air conditioner vents and open windows that may permit cold drafts. Also ensure that indoor temperatures do not fall too low, as temperatures below 50°F are unideal for tropical houseplants.
Chlorosis is the condition where the leaves of a plant turn yellow, and it can sometimes be triggered by nutrient deficiency, particularly nitrogen and potassium, which are macronutrient in plants.
A lack of one or both of these nutrients will cause the lower and older Hoya leaves to turn yellow before falling off. In addition, new leaves will appear pale green and wrinkled.
Besides potassium and nitrogen, deficiencies in calcium, iron, manganese, and sulfur may also cause yellowing and stunted growth of new leaves. Still, as these are micronutrients, they may not be as severe as nitrogen and potassium deficiencies.
You can correct nitrogen deficiency with a tablespoon of fish fertilizer diluted in one gallon of water. The mixture can then be sprayed over the stems and leaves of the Hoya and used to water it.
Alternatively, water the plant once a month with a mixture of one part liquid fertilizer and five parts water.
To avoid possible over-fertilization, which is another cause of chlorosis, then it is best only to apply fertilizer after other likely reasons for yellowing leaves like improper watering and lighting have been ruled out. Also, do not apply fertilizer to plants in winter, as most plants do not grow around this time.
Sometimes, yellow leaves are the result of age and not any underlying problems. The lowest leaves are the oldest on the plant, and after some time will turn yellow and fall off.
There is no solution to yellowing brought on by age, as it is a part of the plant’s life cycle. You can snip off yellow leaves with sterile scissors if they are unsightly.
When age is the cause of yellowing, it is usually restricted to a few bottom leaves at a time, while the remaining foliage remains a healthy green.
Can Yellow Leaves Turn Green Again?
Except in cases of nutrient deficiency, and low lighting, it is unlikely that yellow leaves will eventually revert to their original colors. Take the required corrective measure, then snip off the affected leaves.
Wilting Hoya Leaves
Wilting refers to the condition when the leaves on the plant become limp and hang lifelessly from the stems as a result of diminished water levels in the plant.
Like yellow leaves, the main cause of wilting is water stress. Still, high temperatures and pests like mealybugs may also be responsible for wilted leaves.
Wilted leaves are not frequently observed on hoya plants as the thick and waxy nature of the leaves retards wilting. Consequently, when the leaves begin to wilt, it may be too late to salvage the plant. Hence it is better to prevent wilting from happening in the first place.
Water stress refers to watering conditions that do not fit the requirements of the plant. Water stress can either be in the form of overwatering or underwatering.
In the case of underwatering, the plant doesn’t get enough water from the inception, and so appears weak and tired.
In overwatering, however, there is too much water in the soil, which cuts off the roots’ oxygen supply and eventually leads to root damage. Consequently, the plant can not take up water to the leaves, and wilting is the result.
If you must default in watering, it is better to underwater the plant than to overwater it, as the effects of underwatering can most times be reversed simply by wetting the soil. On the other hand, wilting caused by overwatering is not as easy to reverse, as the roots, hidden from view, would have been significantly damaged before the leaves begin to show signs.
Thus, it’s important that you water hoya plants with moderation following the methods discussed earlier.
Insect pests like mealybugs and aphids suck the juices from leaves and stems of the plant, resulting in wilting, yellowing, and eventual leaf drop. If left unattended, mealybug infestations will eventually kill the plant.
Fungus gnats are black flying insects that flit around plants. The adult gnats are not harmful, but they lay eggs in moist soils, and the resulting larva feeds on the roots, severe infestations can lead to wilting, amongst other problems.
Overwatering is the primary cause of fungus gnat infestations as adults like to lay eggs in moist soil. Consequently, control fungus gnats by limiting the watering frequency.
Hoya Leaves are Falling Off
While the sight of falling Leaves can be alarming, it is not always a sign of an underlying problem, as it’s part of a plant’s natural life cycle to shed older leaves so energy can be redirected into producing new growth.
It is important to be able to differentiate natural leaf shedding from one caused by a problem, as this will determine how you respond to the problem and if you will be able to correct the situation and salvage the plant.
When the leaves at the bottom of the plant turn yellow and fall off, there is usually no cause for worry. However, when random leaves, even the newer ones, begin to turn yellow and fall off, it is an indication of an underlying issue that needs to be addressed immediately. Possible reasons why the leaves of a Hoya plant are falling include water stress, pest infestation, diseases, and root rot.
Diseases of Hoya Plants
Diseases that afflict Hoya plants are mostly fungal, and they are frequently caused by overly moist conditions.
This disease appears as a grayish patch in the middle and edges of hoya leaves. The affected leaves are usually those leaves in the middle of the plant, as this is where there’s the most moisture. The disease is most common in the winter.
Control involves reducing the humidity around the plant. Copper fungicides will also work to treat the disease.
Stem and Root Rot
Root rot results from overwatering, which encourages fungal development. As such, the control will be to stop watering for some time.
However, if on inspection, the entire root system is blackened and mushy, there is no remedy, and you should discard the plant.
Hoya Plant Pests
Besides mealybugs and fungus gnats, other hoya pests include mites, aphids, thrips, and scale insects.
Some caterpillars will eat hoya leaves, but as they soon change into butterflies, they are not usually much of a problem. Besides, hoyas are usually not the first choice of food for caterpillars.
Mites are tiny, almost microscopic organisms that feed on the sap of leaves. The presence of mites can go unnoticed, as infestations appear as dust layers, which some people may overlook. Mites cause leaves to curl and become stunted and deformed.
There are different species of aphids, but the one common to hoya plants is the Oleander aphid, which is yellow with black limbs. The presence of aphids can often go unnoticed until the emergence of honeydew and sooty mold. Aphids cause the deformation of new leaves.
Neem oil is effective in combating mite and aphid infestations.
Repotting Hoya Plant
Repotting is an effective way of addressing yellowing and wilted leaves caused by root rot from overgrown roots, compacted soils, and fertilizer root burn. The repotting process is as follows
- Turn the pot on its side and press around the body to loosen the roots.
- Gently slide the plant out if the pot
- Break off any remaining soil on the root ball and cut off damaged roots.
- Transfer the plant to a new container with fresh, well-drained soil.
Note that the best time to repot hoyas (and plants in general) is in during the growth season (spring and summer months) as this is when the plant is better able to deal with the strain, but in the case of severe chlorosis, it is best to transfer the plant as soon as possible if it is to have any chance of survival, as waiting will only make the condition worse.
Water stress, particularly overwatering, is the primary cause of hoya leaf problems of yellowing, curling, wilting, and falling.
The water needs of the hoya plants can change depending on the season and the temperature and humidity. As such, it is best to water hoya plants only when the soil is almost dry to avoid water stress-related problems.
Other likely culprits include nutrient deficiencies, unsuitable lighting, cold drafts, poorly drained soils, pests, and diseases.
Repotting hoya plants is an effective way of combating leaf problems stemming from root rot, pest infestations in the soil, and compacted soils.