Hoyas are very popular houseplants because of how low maintenance they are. Their beautiful vines, waxy leaves, and clusters of pretty flowers are some of the aesthetic reasons they make great indoor plants.
One of the most common problems encountered by hoya owners is when the plant’s leaves turn brown.
The causes of browning hoya leaves include too much sunlight, underwatering, overwatering, transplant stress, frost damage, too much or not enough nutrients, disease, and pests.
In this article, we will discuss these causes of browning hoya leaves, and how to remedy each one.
If you are experiencing this problem and wish to learn more, just keep reading.
Why are my hoya’s leaves turning brown?
Too much sunlight
One of the most common reasons a hoya’s leaves turn brown is that it is getting too much sunlight – specifically, direct sunlight.
When the plant’s leaves get too much direct sunlight for extended periods of time, it can cause the leaves to burn and become brown and crispy.
Hoyas prefer bright, indirect light. These plants typically grow on the ground, on rocky coastal landscapes, or on the trunks of trees as epiphytes. This means that they do not get a lot of direct light in their natural habitats. To keep these plants happy, you need to emulate the sunlight they might get in nature.
The moment you notice browning on the tips of your plant’s leaves, move it to a shadier spot immediately while you decide on a new spot for it to live.
If you are keeping your plant outdoors, keep it under the shade of a large tree or on a patio or porch where it will get shade for several hours a day.
If you keep your plant indoors, place it near an east- or west-facing window, as opposed to a south-facing window that might let in light that is too harsh. If the only windows in your home are letting in harsh light, you can diffuse it by placing a sheer curtain over the window.
However, just because the plant likes to be in the shade some of the time, this does not mean you can deprive it of light altogether. All plants need light to survive and thrive, and although you are afraid of burning your plant, remember that it still needs light to photosynthesize, so make sure it still gets its daily requirements.
If you live in a place with winters where natural light is scarce, you can help your plant out by buying a grow light. Plants cannot tell the difference between sunlight and artificial light, so they will do just fine in this scenario.
Underwatering
Another reason your hoya’s leaves are turning brown maybe that it is not getting the water it needs.
If you neglect to water the plant when you are supposed to, or if the plant is kept in a spot where it gets too much sunlight causing the soil to dry out quickly, or if you used soil that is too loose and does not hold moisture well, this can all lead to shriveled and brown leaves.
Plants need water not only to keep their leaves vibrant and healthy; it is also the vessel they use to carry nutrients from the soil into their roots. If there is no water in the soil, the plant will be deprived of nutrients as well as dehydrated.
Fortunately, underwatering is easy to fix. If you think your plant has not been getting as much water as it needs, all you need to do is to water it immediately.
Flood all of the soil in the pot with water until you can see excess water dripping from the drainage holes at the bottom of the pot. Flooding the soil ensures that all of the roots can have access to water and will have a chance to recuperate.
The leaves that have turned brown from drying out cannot be returned to their original state, so if you do not like the aesthetic effect of the brown leaves, you can always cut them off using sterile scissors so that only healthy, green leaves remain.
The best way to avoid underwatering is to understand when to water the plant. To do this, you will need to check the soil by touching it. If the top two inches of soil are dry, that means the plant needs to be watered, but if the top two inches of soil are still a bit damp, wait one or two days before checking again.
Overwatering
If you give the plant too much water, this can lead to overwatering which will also cause its leaves to turn brown.
Overwatering can be due to giving the plant too much water every time you water it, or watering it more often than you need to. It could also be because the soil in the pot is too dense and retains moisture too well, the pot does not have drainage holes and the plant is standing in soggy soil, or you did not adjust your watering schedule according to changes in the weather or the season.
The leaves will turn brown because the plant will absorb too much water from the waterlogged soil, and the cells in the leaves will burst from the overwhelming water content. These ruptured cells will start as brown spots that will spread until the entire leaf is affected. This phenomenon is called edema and is an effect often observed in plants that have been overwatered for some time.
Hoyas can absorb a certain amount of moisture that they store in their leaves and stems for times of drought. This means that they do not need their soil to be constantly wet in order to be happy.
The roots also need to be able to dry out between watering because they can only absorb oxygen when they are dry. If a plant’s roots are perpetually standing in wet soil, they will be unable to get oxygen and could drown and die. This can lead to a serious consequence of overwatering, known as root rot.
Root rot is what happens when the roots drown in waterlogged soil. The roots will begin to rot, and this weakness will allow opportunistic pathogens to attack. These pathogens, which are fungi and bacteria, will make the rot more aggressive and soon it will spread to the rest of the plant and could even kill it.
You will know a plant has root rot if the leaves and stems have turned yellow or brown and feel soft and mushy to the touch, while the soil in the pot is constantly wet.
In order to save an overwatered hoya, you need to stop watering it immediately. Let the soil in the pot dry out before watering it again.
If you want to check whether your overwatered plant has root rot, you will need to remove it from the pot. Wash off as much soil as possible from the roots, as gently as you can. Inspect the roots closely for sections that are brown or black. These roots are rotten and will need to be removed.
Use a sterile pair of scissors to cut off the rotten roots until only healthy, white roots remain.
Then lay the plant on a dry paper towel to allow the roots to air dry for a few hours.
Prepare a new pot and make sure it has drainage holes at the bottom. These drainage holes will allow any excess water to flow out, rather than sitting stagnant in the pot.
Fill the new pot with fresh potting soil that is not too dense. Place the plant in the soil and cover the roots with more soil.
Do not water the plant after repotting it, in order to give the roots time to recover from the trauma of repotting.
Just like with underwatering, the best way to avoid overwatering is to know exactly when to water the plant. As mentioned above, check the soil by touching it. If the top two inches of soil are dry, water the plant, but if the soil is still a bit damp, wait one or two days before checking it again.
Transplant stress
Another reason hoya leaves turn brown is that they have either just been repotted or have just been moved from one place to another without having time to adjust.
This plant, in particular, does not take well to these kinds of changes and they will indicate their stress through wilting and browning leaves.
This can be so bad that their leaves can even start falling off.
When a plant is growing in a nursery, it is living in ideal conditions. The moment you take it home with you, you are exposing it to different temperatures, humidity, watering schedules and light.
These changes may not seem like much, but for a plant they can be quite drastic, which is why it can become stressed.
When you take a new hoya home, do not worry if it displays signs of stress; this is normal. The best you can do in this situation is to provide the plant with as close to ideal conditions as you realistically can, and it should be able to bounce back in a few weeks.
If you want to move an indoor hoya to the outdoors, this could also lead to transplant stress, so make sure you make the move gradually.
Place the plant outdoors for one hour on the first day, and then every day add 30 minutes to the time the plant spends outside. Continue this until the plant can tolerate spending the entire day outdoors, but it should still spend a considerable amount of time in the shade.
Frost damage
The hoya’s natural habitat is the tropics, so it is not the best at surviving cold climates.
When a hoya is exposed to frost, its leaves will be damaged. By the time they have thawed out, there will be brown spots on them.
This damage is irreversible, so you will need to remove the damaged leaves from the plant if you do not like seeing them.
Bring the plant in from the cold, especially if you live in a place that has severe winters.
When indoors, make sure that your plant is not placed anywhere near an air conditioner or in a spot near a door or window where it can get hit by cold drafts. These cold drafts can also cause the plant to dry out and turn brown.
Too much or not enough nutrients
If you give your hoya too much fertilizer, this can also cause its leaves to turn brown. Fertilizers contain salts that can suck up the moisture from the soil and dry out the plant.
Hoyas get plenty of nutrients from their potting soil, so they do not need to be fertilized often. If you think the plant is not growing well, then you can feed it, but only when it is necessary.
Not giving the plant enough nutrients, on the other hand, can also lead to the leaves turning brown. Hoyas need copper, manganese, zinc, iron, potassium, molybdenum, magnesium, phosphorus and nitrogen to survive.
The signs of nutrient deficiency can be noticed earlier on older leaves than on younger ones. This is because, when a plant does not have enough nutrients, it will prioritize its younger leaves because they need fewer resources to stay alive. The older leaves will essentially be sacrificed to make sure the younger leaves are kept alive for longer.
Disease
Diseases caused by fungi can also turn the hoya’s leaves brown.
Anthracnose infection, caused by the Colletotrichum fungus, leads to brown spots appearing on the leaves. The brown spots will have gray spores, and the condition typically affects hoyas that live in warm and humid places.
If you are not able to catch the infection in its earlier stages, the spores can spread to your other plants through the elements, insects or contaminated gardening tools.
If your plant has open wounds they are easier to infect, so try to keep the wounds clean and make sure you clean your tools before using them on another plant.
Another fungal disease that affects hoya plants is Septoria leaf spot. This disease is caused by the Septoria lycopersici fungus and also commonly affects tomato plants. This disease can cause brown spots with yellow halos, and the longer the disease is allowed to persist, the larger the spots become until they consume entire leaves.
Botrytis cinerea fungi can also cause the leaves to turn brown and mushy. The plant will rot as the leaves start to fall off. You will also see brown or black lesions on the plant’s stem.
Alternaria leaf spot is another fungal disease that affects not only hoyas, but many other vegetable and fruit plants as well. Brown spots will appear in the early stages of the disease and, as it becomes more serious, lesions will begin to appear on the stems. If the disease is left untreated, the plant will wither and die.
For hoyas that are grown in humid places, powdery mildew is a common problem. This is caused by different fungi and also affects plants other than hoyas. The disease will present as grayish-white powder on the leaves, and eventually, the leaves will turn yellow or brown.
The Erwinia carotovora bacteria causes a bacterial leaf spot on hoya plants, particularly those kept in warm and humid places which are conducive to bacterial growth. Yellow and brown spots will appear on the leaves, and there may also be blisters at the bottom of the leaves as the disease gets more serious.
If you think your plant is diseased, separate it from your other plants immediately. Keep it in quarantine while you treat it and until you are sure it is back to normal.
Use a fungicide on the plant, spraying it once a week for as long as needed.
You can also remove the affected leaves and stems. Make sure you dispose of the affected foliage properly, because they may be harboring spores that can spread to other plants.
Pests
The most common pests on hoyas are spider mites, scale insects, aphids, and mealybugs.
All of these insects feed on the sap in the leaves and stems of the plant. The bites on the foliage, where the insects suck the sap, will leave brown spots. The larger the pest population on your plant, the more noticeable these brown spots will be.
Unfortunately, it can be difficult to spot these tiny pests during the early stages of an infestation. As a precaution, you should inspect the plant for pests, including the bottom of its leaves, every time you water it.
You can get rid of these pests by separating the affected plant from your other plants to avoid spread, and then using a hose to knock the pests off with a strong stream of water.
You can also use an insecticide, but if you do not like using chemicals around your house, there are some home remedies you can try.
You can spray the pests directly with rubbing alcohol, which should be enough to kill them.
You can also mix two tablespoons of mild dish soap with water and use this solution as a spray.
Or, if you have neem oil, mix two tablespoons of oil into a spray bottle of water and spray the solution on the pests.
No matter which method you use, repeat it once a week for four weeks, extending for a few more weeks if needed.
Conclusion
Hoyas are popular houseplants because they are low maintenance and have beautiful foliage. These are tropical plants that may not do so well in places with proper winters.
One of the most common problems encountered by hoya owners is the leaves turning brown.
The most likely reasons your hoya’s leaves are turning brown are too much sunlight, underwatering, overwatering, transplant stress, frost damage, too much or not enough nutrients, disease, and pests.
In order to prevent the browning of a hoya’s leaves, start by choosing a healthy plant from the nursery. Acclimatize the new plant to your home by providing it with as close to ideal conditions as possible.
Use the right soil and pot for the plant, and only use sterile gardening tools. Remove any diseased or browning leaves from the plant and make sure you dispose of them properly.
Place the plant in a spot where it gets bright, indirect light and only water it when the top two inches of soil have dried out.
If you live in a place with winters, take the plant indoors before the frost starts, because this plant is sensitive to low temperatures.
Finally, make it a habit always to check the leaves and stems of your plant for signs of disease when you water it. This way, you will be able to catch any disease or pest infestation in its early stages.
Image: istockphoto.com / yilmazsavaskandag