Why is my Dumb Cane / Dieffenbachia turning yellow?

Last Updated: December 31, 2021

Dieffenbachia plants get a bit of a bad rep as they are quite toxic to humans and pets. However, if you look past this, they have some of the most incredible foliage (as well as flowers if you’re lucky). However, if the care or environment isn’t right for your Dumb Cane plant, then your plant might start to develop yellow leaves. There are several factors that might cause yellow leaves on your plant, so it’s important to figure out what is happening to your plant. Below we will be going through each of the different reasons in detail, so you can diagnose the issue, fix it and even prevent it from happening again in future. 

Consistent overwatering

Let’s start with probably the most common cause of yellow leaves on Dumb Cane plants – overwatering. Although your plant likes to have some moisture in the soil, they don’t do so well if it becomes quite waterlogged as their roots will begin to rot. Once the root system becomes damaged, your plant will struggle to take in enough nutrients, water and oxygen which will impact overall plant health and cause the leaves to turn yellow. You might also notice the stems and leaves going quite soft and droopy. 

Before changing anything in your watering routine for your Dumb Cane you want to be 100% sure that overwatering is the issue. To do this, take your plant out of its pot and see if the potting mix is waterlogged and clumpy! You can also check the soil using a moisture meter to determine if it’s waterlogged. They are a great investment for all plant parents – a lot cheaper than having to buy new plants!  If there is a lot of moisture in the soil then this is most probably why your Dumb Cane plant has yellow leaves. Replace the potting mix straight away if it is waterlogged so your plant can begin to recover. 

After a few weeks, you should start to see your Dumb Cane becoming stronger and maybe even producing new healthy growth. Be patient though as your plant has been through a lot and will need time to recover. Make sure to adjust your watering schedule going forward, allowing time for the potting mix to fully dry out before watering again. 

Temperature extremes

Another factor that can harm your Dumb Cane and cause yellow leaves is really high or low temperatures. If your Dumb Cane is too close to a window that gets a lot of direct sunlight or if it’s closer than a meter from a radiator/ heating vent then the hot air can dry out the plant. To avoid this, ventilate the room well and keep all plants away from radiators, heaters or cookers as this can really dry out the leaves and turn the leaves yellow.

Cold air can also be harmful to your Dumb Cane and may also be why your plant has developed yellow leaves. Make sure there are no drafts coming through the windows or doors that your Dumb Cane (or any other houseplants for that matter) is near. It is also a good idea to buy a digital thermometer to keep track of how the temperature changes throughout the seasons and you will be able to spot any cheeky drafts or hotspots that might be damaging to your plants (extreme temperatures can cause a whole range of issues beyond yellow leaves).

Too much direct sunlight hitting the leaves

Another cause of yellow leaves on Dumb Cane plants can be sunburn caused by high levels of direct sunlight. This is most common during summer as not only is the sun out for more of the day, but it’s a lot stronger too which can cause problems for the relatively thin leaves on a Dieffenbachia plant. 

Unfortunately, once the leaves on your Dumb Cane have turned yellow there is no reversing it so your best option is to remove the most affected leaves and find a new spot for your Dumb Cane. Ideally, you want somewhere will bright but indirect light. 

A lack of nutrients can cause yellow spots

Yellowing leaves on Dumb Cane plants can also be caused by a lack of nutrients. This is more common in older, more mature plants as over time the potting mix will become nutrient deficient if not given any fertiliser. Intense watering can also flush out the nutrients so that’s also something to be wary of.

There are two methods that will help to increase the level of nutrients in the potting soil and prevent any more yellow leaves. Firstly, remove all of the old soil in the pot and replace it with new nutrient-rich houseplant potting soil. (Remember to make sure it is also well-draining to avoid waterlogging). You can also use a well-balanced houseplant fertiliser at half strength. Our houseplants have always liked the liquid fertiliser from Miracle Gro which is available from Amazon here.

Pests are a rarer but worrying cause of yellow leaves

Pests such as aphids, spider mites or scale insects may be hiding on your plant and sucking on the leaves. This exhausts the leaves and causes them to develop yellow patches or small yellow spots. If you suspect that pests might be behind the yellow leaves on your Dumb Cane, use a magnifying glass to inspect the plant (remember to look at the undersides of the leaves as this is where they particularly like to hide). If you do spot unwanted visitors on your plant, isolate it from all of your other houseplants to stop the infestation from spreading. Also, it’s a good idea to check over the plants in the same room just to make sure that none of your other plants has pests. 

Then trim off the worst affected leaves on your Dumb Cane to curb the infestation a little before showering your plant and treating with neem oil.

So those are all of the various reasons why your Dumb Cane plant has developed yellow leaves. It’s important that you act quickly after diagnosing the problem as any more damage could be the difference between being able to save your plant and having to say goodbye to it. If you do change your watering schedule, or relocate your plant to another spot in your home, make sure to keep a close eye on it to see if any other problems develop or if the yellow leaves continue. 

To learn more about how to care for your plant, spot and solve other common problems as well as the different propagation methods, check out our Dumb Cane care guide.

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