Dieffenbachias (Dumb Canes) are popular houseplants because of their vibrant, variegated foliage.
Even though dieffenbachia is easy to take care of and pretty flexible, the leaves often turn brown.
Dieffenbachia leaves frequently turn brown due to sunburn, underwatering, or overwatering. Low humidity, temperature stress, lighting issues, pests, diseases, and nutrient deficiency all can cause problems. Keep your dieffenbachia well-watered and out of direct sunlight to keep the leaves from turning brown.
Examining your plant and its growing conditions will reveal the problem. I’m here to help you every step of the way.
Overwatering is the most common cause of dieffenbachia leaf browning. If you give your houseplants too much attention, this is likely the cause.
Too much watering makes the soil soggy or waterlogged for a long time. As a result, airflow to the root system is limited.
Your dieffenbachia will be suffocated by soggy soil. Your plant’s healthy functioning relies on oxygen uptake, and roots play an essential role in this process.
Photosynthesis, cell formation, and other processes in your plant are impacted when the roots are damaged by overwatering. This causes widespread but gradual browning of the leaves.
Without addressing the problem of overwatering, the plants’ roots will become more vulnerable to bacterial and fungal diseases.
In addition, rot can spread upwards to the stems and foliage, causing browning or darkening.
Overwatering is to blame if your dieffenbachia’s leaves are browning and wilting despite your best efforts to keep them well-watered. You can tell an overwatered dieffenbachia by feeling the soil.
The pot may be heavier than usual because the soil is saturated. Additionally, dieffenbachias that have been overwatered show signs such as:
- Dropping of leaves at random.
- Mold or mildew growth on the soil’s surface.
- After watering, the soil takes far too long to drain.
- Getting a smell of rotting plants from the soil.
Root rot is frequently accompanied by the last of these symptoms.
Take your dieffenbachia out of its pot and inspect the roots if you think this is the case.
Roots that are soft, mushy, and have brown or black roots are apparent signs.
Overwatering isn’t caused solely by overwatering dieffenbachia. It can also be caused by several other factors, such as:
- Not reducing the watering frequency in the fall, winter, or colder weather.
- You are planting dieffenbachia in a potting mix that is poorly drained.
- After watering your dieffenbachia, forget to empty the drip tray or cachepot.
- Planting your dieffenbachia in a container that is too large for it.
- Grow your dieffenbachia in a pot with no drainage holes.
- You are putting your dieffenbachia in a dark or poorly-aerated location.
Solution for Overwatering
If you catch the problem early, you can save your dieffenbachia before root rot.
Allow at least the first two inches of potting soil to dry out entirely before resuming watering.
You must also treat other secondary factors, such as:
- Poor drainage – Ensure the potting mix and container are well-draining
- Insufficient drainage holes – Switch to a pot with several drainage holes.
- Wrong size pot – Repot your dieffenbachia into a proper-sized container
- Slow draining – Replant your dieffenbachia using a well-aerated, fast-draining potting medium (Amazon link).
- “Wet feet” – Make sure to empty the cachepot/drip tray 5-10 minutes after watering your dieffenbachia.
- Poor light conditions – Position your dieffenbachia where it’ll get plenty of medium to bright yet indirect light for at least six hours a day.
Things can get a little worse if the roots have begun to decompose. So before repotting your dieffenbachia, you’ll need to remove the diseased roots and dip the healthy ones in a fungicide solution.
Underwatering and overwatering can both cause dieffenbachia leaves to turn brown.
However, if your dieffenbachia’s browning leaves are dry and crispy, you may have neglected to water them for a while.
Underwatering makes yellow before brown. Dehydration affects older, lower leaves and new growths.
This means that the browning of leaves will happen in a symmetrical pattern, such as from top to bottom.
Because dieffenbachia is drought-resistant, spotting an underwatered dieffenbachia should be simple. When the leaves turn brown, the soil should be dry.
Your planter should be light in weight. Your dieffenbachia will look withered, wilted, and dried out. Curling, wrinkling, and stunting are also symptoms.
Your dieffenbachia’s water requirements will likely rise if you neglect to water it.
Perhaps it is exposed to direct sunlight, or warmer weather has arrived.
In the spring and summer, you may notice that your plant is growing rapidly and requires more water.
How to Fix
First, see if your dieffenbachia has become rootbound or if the pot is too small. If either of the two is confirmed, you will need to use a one-size-up container.
When the foliage turns brown, the soil will have dried out. Soaking in a bathtub, basin, or sink full of water is recommended for bone-dry soil.
- Allow the pot to soak up water for 30-45 minutes or until saturated.
- Remove the pot from the sink and allow it to drain completely.
- After 10 minutes, empty the cachepot or drip tray to stop water from pooling.
- Improve the humidity around your plant to avoid dehydration.
Fortunately, dumb canes are hardy and will return to total health when you return to a regular watering schedule.
To avoid stressing your dieffenbachia, I suggest watering slowly for about a month before making any pruning decisions on the brown leaves.
Although dieffenbachia plants can tolerate shade, they prefer indirect bright light.
Nonetheless, prolonged exposure to direct sunlight can be hazardous to your plant, as dieffenbachia leaves are prone to drying out and scorching from the sun.
Sunburn will appear on the leaves as large brown spots or patches.
The entire leaf will turn brown if the problem is not addressed due to extreme scorching.
Too much light also indicates that your dieffenbachia requires more water due to the extreme dehydration and the leaves brown.
Avoid placing your dieffenbachia in direct sunlight for more than two hours a day to prevent sunburn.
Ideally, your dieffenbachia should be exposed to at least six hours of sunlight each day.
Use a good light meter to find the ideal conditions for your houseplants.
Browning leaves on your dieffenbachia can also be caused by bacterial or fungal diseases.
They cause leaf tissue to rot and stop working correctly, causing leaves to turn brown, necrotic, and eventually fall off.
The most common cause of dieffenbachia developing fungal and bacterial diseases is excessive moisture.
However, poor sanitation may also contribute to the spread of pathogens and worsen the situation.
Keep an eye out for the following common diseases that can cause dieffenbachia leaves to turn brown:
- Anthracnose: Caused by Collectrotrichum and Gloeosporium fungi, this fungal disease begins as small, tan to dark brown spots on mature leaves. Brown lesions with a yellow halo affect lower inner foliage before spreading. Yellow leaves turn brown and die.
- Bacterial Leaf Spot: Erwinia carotovora or Erwinia chrysanthemi are two types of bacteria that often cause this disease in dieffenbachias. Symptoms include small dark green or grayish leaf spots. They’ll grow, become irregular, and turn brown, tan, or black. They may be wet and have a yellow halo.
- Myrothecium Leaf Spot: This fungal disease, caused by Myrothecium roridum, results in the formation of outsized oval leaf spots at the margins or tips of the leaves. They can range in color from gray to dark brown.
Treatment and Management of Dieffenbachia Diseases
The appropriate treatment and control regime will be disease-specific.
- To treat Anthracnose leaf spot disease, a protective fungicide, such as copper-based products, must be applied regularly (Check the latest price on Amazon here). To avoid reinfection, avoid overwatering and overhead irrigation.
- Chemical treatments for Bacterial Leaf Spots are rarely successful. Your best bet is prevention. Remove infected foliage and avoid overhead irrigation or leaf splashing.
- On tender growths, Myrothecium Leaf Spot spreads more quickly. As a result, avoid using too much high-nitrogen fertilizer. I recommend spraying your dieffenbachia with a fungicide.
 Poor Water Quality
Most Araceae plants are sensitive to mineral and chemical deposits in irrigation water.
Therefore, they are incredibly picky about irrigation water, especially softened or tap city water.
Most municipalities, cities, and territories add chlorine and fluorides to their drinking water to prevent tooth decay.
Salts and other phototoxic chemicals are also common in city tap water.
Unfortunately, these chemicals and mineral salts can accumulate in the growing medium to toxic levels.
In addition, they will burn the roots, preventing your dieffenbachia from absorbing nutrients and water. The symptoms include browning or yellowing of the leaves.
High levels of chlorine and fluorides can also cause leaf tip/edge burn. These edges will be dry and brown.
The quick fix is to flush excess mineral deposits and chemicals from the soil with a large amount of distilled water.
In the future, use distilled or rainwater to water your dieffenbachia. Then, you can invest in a good water filtration system for a one-time solution.
If you have no other choice but to use tap water, store it in an open container overnight.
The chlorine and fluorides will evaporate, leaving behind water suitable for houseplants.
 Temperature Extremes
Dieffenbachias thrive in 60 to 75°F (15 to 24°C). Temperature stress symptoms will appear if your dieffenbachia is exposed to temperatures outside of this range.
One of the most common responses of your plant to stress is for the foliage to turn brown or yellow.
This is because dieffenbachia does not generally function outside its ideal temperature range.
This is especially noticeable when there is a sudden temperature change or when you are exposed to drafts.
You should keep your dieffenbachia out of drafty areas near open windows, air ducts, entryways, etc.
Place a digital thermometer next to your dieffenbachia to monitor the ambient temperature.
It’ll give your max and min temperatures recorded, so you can gauge if the spot is ideal.
Ensure your dieffenbachia isn’t sitting next to heaters, fireplaces, or heating vents.
 Low Humidity
Dieffenbachia is a the Caribbean and South American tropical plant. Low humidity stresses your dieffenbachia, causing browning and leaf drop.
Dieffenbachia leaves turn brown when moved from high to low humidity.
Your plant will quickly develop brown leaf tips and edges to adjust to new conditions.
This happened when I brought my dieffenbachia home from the nursery.
In the winter, when you run your central heating system, the air in your home can become hot and dry.
Solution for Brown Leaves on Dieffenbachia Caused By Low Humidity
I’d recommend keeping an eye on the humidity levels in your home and around your dieffenbachia.
In my house, I frequently use a digital thermometer-hygrometer (check the latest price on Amazon here) to keep track of both temperatures and humidity.
I recommend keeping humidity levels above 40% around your dieffenbachia throughout the year.
Some dieffenbachia species, such as D. seguine, require humidity levels of 60% or higher, which is what I aim for to keep my collection happy.
A high humidity level encourages vigorous and robust growth in your dieffenbachia. To increase the humidity around your plant, try the following methods:
- By grouping your houseplants, you can keep the humidity high.
- Make use of a pebble humidity tray.
- Although not strictly necessary, your dieffenbachia will not object to the use of a humidifier.
- Move your dieffenbachia to a naturally humid area, such as the kitchen or bathroom.
- When the weather is dry, consider misting your dieffenbachia.
 Frost Damage
Although dieffenbachia is very hardy, it cannot tolerate frost, cold drafts, or temperatures below 60°F (15°C).
You’ll probably notice that the affected leaves are near open doors and uninsulated windows.
Browning the leaves may also occur if your plant is exposed to cold drafts.
Other symptoms include leaf softening, wilting, loss of lower foliage, and leaf browning.
This gives your dieffenbachia a palm-like appearance.
In extreme cases, Frost damage can cause soggy or mushy leaves, allowing opportunistic fungal and bacterial infections to enter.
- Bring your dieffenbachia indoors when temperatures dip below 60°F (15°C).
- Keep your dieffenbachia away from cold drafts.
- Keep your plant away from un-insulated windows and open doors during winter.
 Repotting Shock/Acclimation
When you repot, relocate, or change the growing conditions of your dieffenbachia, it will go through a period of shock. The stress will cause your plant’s leaves to turn brown.
Browning can affect only the tips, the edges, the dying older foliage, or the entire leaf.
This is incredibly aggressive if you manipulate the roots during the repotting process (such as pruning them off).
Once your plant has acclimated, the leaves of your dieffenbachia should stop turning brown.
Everything should be fine for repotting as long as you use the proper potting mix and container.
Focus your efforts on providing the best possible care for your plant.
 Pest Infestations
Aphids, mealybugs, spider mites, and scale insects are common pests of dumb cane.
As they sip the vital juices from your dieffenbachia, these sap-sucking insects will cause significant leaf browning.
In addition, some may secrete honeydew, which promotes the growth of black sooty mold.
Spider mites are so small that they can’t be seen with the naked eye. As a result, they’re especially hazardous to your dieffenbachia.
Keep an eye out for fine cottony webbing between the leaves or on the undersides.
To deal with and eliminate dieffenbachia bugs, employ a multi-pronged approach. Among the methods I’ve found to be effective are:
- Manually remove bugs by wiping leaves and stems with rubbing alcohol and handpicking.
- A solid water blast is used to blast the bugs off your dieffenbachia.
- Weekly insecticide spraying with neem oil, pyrethrum-based insecticide, or soap spray.
- Utilize natural pest predators.
Should I Cut Brown Leaves Off Dieffenbachia?
Yes, removing the brown leaves from your dieffenbachia will help. This is especially true if you suspect a fungal or bacterial infection is to blame.
However, if the cause is non-contagious, such as humidity, light, temperature, or sunburn, you should wait a month for your plant to fully recover and develop new growth.