Dumb cane plants are one of the most common types of houseplants. Beginner gardeners love them because they are relatively easy to grow. They are also easy to purchase in most nurseries and online.
However, even the easiest plants can become sickly if they’re not cared for properly. Yellowing and browning leaves are a common problem among dumb cane plants.
Usually, yellowing and browning leaves are swiftly dealt with once you identify the cause of the discoloration in the first place.
By closely observing your dumb cane plant and taking regular care of it, you can prevent discoloration and take swift action to help your plant recover if the leaves start to turn yellow.
What Is Dumb Cane?
Dumb canes are a type of leafy tropical houseplant known for their colorful leaves and lush, bushy growth. They are also called dieffenbachia or mother-in-law’s tongue.
There are dozens of varieties of dumb cane plants that have different leaf patterns. Some of the most common are Camille, with pale yellowing leaves; Carina, with darker patches throughout their leaves; and a smaller variety called Compacta.
Dumb cane got its name because of its poisonous properties. The plant’s sap contains calcium oxalate crystals that cause a person or animal’s mouth to swell up when ingested, often making the victims unable to speak. This is where the name “dumb cane” comes from since the plant can strike unwitting opponents dumb.
Ingesting dumb cane is unpleasant, but it is not deadly (although some people have needed medical attention). However, households with small children or pets should not keep dumb cane plants. Gardeners should be careful not to touch their faces after handling the plant and to wear gloves when repotting.
Why do people keep dumb cane if it is dangerous? The dangers are minimal, and many gardeners are willing to risk some potential discomfort to keep this beautiful, leafy plant in their home. The streaky leaf patterns brighten any indoor space.
Dumb cane plants are also air purifiers. Many plant lovers keep them in their homes or offices to improve the air quality without spending money on expensive purifying machines.
How to Care for Dumb Cane Plants
Besides its beauty, many indoor gardeners choose dumb cane because it is easy to care for. Unlike fussier house plants such as orchids or elephant ears, dumb cane plants are hardy and do not require much special treatment.
Dumb cane plants do not even require special soil. They thrive in regular peat-based soils as long as their pot has good drainage to avoid waterlogging the plant.
However, dumb cane plants are relatively sensitive to the weather. These plants prefer stable environments and are affected if their living situation changes drastically. They need a warm environment with some humidity.
Dumb canes require several hours of indirect sunlight a day, but they can also survive winter conditions. It is best not to put them in direct sunlight as that can damage them.
When it comes to watering and fertilizing, dumb cane plants are not that demanding. They need to be watered thoroughly once in a while, then can be left alone for days until the soil dries out.
These plants only need fertilizer every few weeks during the growing season. Outside of the growing season, they do not need to be fed at all. They also do not need repotting, unlike other houseplants of this size.
The last thing gardeners need to do is clean dumb cane leaves regularly. Dust or stray water droplets can affect the plant’s ability to photosynthesize, so wiping the leaves with a paper towel or cloth helps keep the plant healthy.
Once a gardener finds a stable environment for their dumb cane, they can pretty much leave the plant alone for days or even weeks. It’s no wonder that this plant is beloved by many houseplant aficionados, as long as nobody ingests it.
How to Identify Causes of Discoloration
Despite the relative ease of caring for dumb cane plants, discoloration on the leaves is still common. Luckily, the color change can also help identify the cause of the problem in the first place.
If the leaves are streaked with yellow and white: If the leaves have a regular distribution of yellow and white streaks, that is actually normal. Dumb cane plants are known for the unique dapplings of their leaves, which form unique patterns on each leaf.
Different varieties have different color patterns, so your dumb cane plant may naturally have yellower leaves than other plants from the same species. When in doubt, compare your plant to photos of similar varieties in online galleries such as this one.
If the leaf’s edges are brown: If a leaf’s edges are brown and curling, that could be a sign of over-watering or overfertilization. To make sure that you’re not over-watering, check the soil moisture: if the soil is wet to the touch, this is a sign that the plant has too much water.
If the brown edges are concentrated in one area, that could be a sign of a problem on one specific leaf, such as water droplets forming.
If the leaves are yellowing and growing smaller: When dumb cane leaves start yellowing and grow closer to the stem, that is usually a sign that the plant is under-watered. Under-watered plants start to gradually turn yellow, so a gradient pattern on a leaf is a sign that the plant is under-watered.
If the leaves look scorched: If several leaves have turned bright yellow and have brown spots, almost as if the plant was burned, then the dumb cane is scorched. It has probably been exposed to too much direct sunlight.
If the leaves are yellowing and falling off: It is normal for dumb cane plants to lose leaves as they age. Although these plants live long, they still show signs of wear and tear. You only need to start worrying if you notice several leaves yellowing and falling off at the same time.
If too many leaves are falling off at the same time, try moving the plant. It may be in an environment that is too cold for it to thrive.
If the leaf has holes and brown spots along with yellowing: Holes rotting away in the leaf are a sign of a serious infection, such as bacterial leaf spot, or pests. Usually, the holes look brown or black and parts of the leaf start falling away. The area surrounding the hole may also start to turn yellow.
This is a serious issue and needs to be treated immediately. Otherwise, pests or bacteria could seriously damage your plant or even kill it.
How to Treat Different Causes of Discoloration
The specific colors of the leaves provide clues as to why the leaves are turning yellow or brown. Once you figure out why the leaves are changing color, the factors that are causing the discoloration are easy to treat.
Over-watering or under-watering the plant: Even though dumb cane plants are fairly easy to take care of, it is still possible to over-water or under-water them. Over-watering soaks the soil, making it difficult for plants to absorb nutrients, while under-watering deprives the plant of nutrients.
It is easy to confirm if water is causing discoloration by checking the soil condition. If you put your finger in the soil and feel a few inches of water-logged soil, you’ve probably over-watered your plant. If the soil is dry to the touch, it needs watering.
Luckily, over-watering or under-watering is one of the easier problems to fix. If the plant is under-watered, just water it thoroughly, then wait a few days. It usually takes a little time for the dumb cane plant to recover from under-watering, and watering it too much immediately will cause damage.
If the plant is over-watered, try to tip out the drainage plate to get rid of excess water and leave it alone. It should recover in a few days. Over-watering can also cause a serious condition called root rot, so you should check the plant’s soil for signs of further damage. Yellowing leaves could be a sign of a far more serious problem.
Root rot occurs when a plant is over-watered and a fungus kills off roots, preventing the plant from getting necessary nutrients. Root rot must be treated quickly by cutting away dead roots, replacing the soil, and cleaning out the pot.
Sometimes the dumb cane plant experiences a process called guttation, when excess water is released through the leaves in a way that makes the plant look as if it’s crying. If the plant also has an excess of fertilizer, these drips can burn the leaves due to the concentration of nutrients in them.
Guttation is easy to prevent and treat. Stop watering the plant and wipe away the excess water on the leaves with a paper towel, which will prevent the droplets from causing further damage.
Overfertilizing or underfertilizing the dumb cane plant: Dumb cane plants do not require a lot of fertilizer, but if they do not receive enough during the growing season, their leaves will turn yellow and shrivel. Adding more fertilizer will resolve this issue.
Adding too much fertilizer can also cause damage to dumb cane leaves. The nutrients in fertilizer can burn the plant if they are too concentrated, causing brown patches that look like burn marks on the leaves.
If you suspect that you’ve overfertilized your dumb cane plant, getting rid of the excess fertilizer is quite easy. Water the plant until some water soaks through to the drainage plate, then tip out the excess water. The water drains the soil and flushes away excess fertilizer, helping the dumb cane plant recover its equilibrium.
Climate issues: Often, the dumb cane plant’s leaves turn yellow because of the weather conditions around it. Too much sunlight, not enough humidity, and drastic temperature changes can affect the leaves.
If the plant is exposed to too much direct sunlight or does not get enough light, the leaves will turn yellow. Simply move the plant to a different position where it will receive several hours of indirect light a day.
Dumb cane plants are very sensitive to temperature changes and drafts. You may think that the cane plant is in a warm enough room, but if it is close enough to a draft source such as an air conditioning vent or an open window, the leaves will turn yellow.
If you’re not sure that low temperatures are causing the yellow leaves, try putting a thermometer near the plant and checking it throughout the day. This will allow you to monitor its climate and decide if moving it is the right course of action.
The dumb cane plant is a tropical plant, but it survives pretty well under various degrees of humidity. However, a lot of dry air will cause yellow leaves, so it is best to move the plant to a damper location.
When you identify a climate problem that is causing yellowed leaves, move the plant immediately. Choose a spot with plenty of natural light where temperature conditions are relatively stable (no cross-breezes, heating or cooling vents, or open windows).
It may take the dumb cane plant a few days to recover and the problem might initially get worse. Drastic weather changes affect the dumb cane plant hardest of all, so after a move, it may look yellowed and droopy. However, this hardy plant usually bounces back after a few days.
Pests and infections: The most drastic cause of yellowing or browning leaves are pests, such as spider mites, and infections, such as bacterial leaf rot. If you identify this as a cause of the color change, you need to take immediate action before the plant becomes seriously ill.
Pests such as aphids and spider mites suck out sap from the leaves, rob the plant of its nutrients, and attract other vermin. You’ll spot aphids on the underside of the plant, along with sticky residue from the sap. Spider mites are not visible to the naked eye, but you can identify them by spotting black dots on the leaves or webs close to the stem.
Getting rid of aphids and spider mites is relatively easy. Spraying cold water or wiping down the leaves with a soapy solution every few days for two weeks will kill off most of the pests. If you have an advanced infestation, you may need to use a chemical insecticide.
If a plant has a dark, rotting spot on its leaf surrounded by yellow, that is the sign of a serious problem called bacterial leaf rot. Leaf rot needs to be dealt with drastically by removing the infected leaves so that the rot doesn’t spread to the rest of the plant.
If you’ve seriously neglected a dumb cane plant, you can still revive the plant by regenerating it. Regeneration is a rather drastic process that involves cutting the plant back until only a few inches of stem remain. After some time, the plant will start growing again.
Regeneration saves a dumb cane plant by cutting away dead and infected areas and giving the plant space to start fresh. The plant will initially lose its beauty, but it is worth it to see healthy growth again.
Treating yellow or brown leaves in dumb cane plants is relatively easy. However, the best treatment is to prevent the plant from getting discoloration in the first place.
Choosing the right spot in the house goes a long way towards preventing discoloration of the leaves. A spot with plenty of indirect sunlight, some humidity, and protection from drafts will help the dumb cane plant thrive.
A dumb cane plant needs to be watered regularly but not too often. A good rule of thumb is to water the plant thoroughly until the soil is soaked through, then to tip the water out from the drainage plate. Do not water again until the soil is dry to the touch.
Watering the plant properly also helps prevent bacterial infections. Always water the plant from the bottom, below any of the leaves and stem growth. Too much moisture on the leaves causes leaf rot.
During the growing season, dumb cane plants need fertilizer every two or three weeks to avoid nitrogen or phosphorous deficiencies. A water-soluble fertilizer at only half strength will help your plant grow and prevent discoloration due to nutrient deficiencies.
When the gorgeous streaked leaves of a dumb cane plant become yellow or brown, that can be a sign that the plant’s conditions are not ideal for its growth. Inspecting the leaves closely and checking for clues on the rest of the plant can help a gardener identify the cause of the issue and treat it.
Most discoloration is easily prevented and treated by keeping dumb cane plants in stable climates, watering them regularly, and fertilizing them during the growing season. If treated properly, these plants can brighten up interior space for many years without demanding too much of a gardener’s attention.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.