Question
Hi, I'm fairly new to indoor plants, well actually all types of plants, and am absolutely in love with Dieffenbachia and Succulents.  I have a Triumph I believe and wanted to find out if you could explain why the lower leaves are yellowing.  They started turning yellow real fast.  I watered thoroughly recently and afterwards it started turning yellow.  I purchased it from H.D. in early January and have not repotted it.  It's a nice sized plant as you can see in the pic and I really do want to keep it flourishing.  I also have a Camille with the same symptoms.  I have them in my south facing living room with lots of indirect light.  There is new growth on the top but would still like to know if I should expect the rest of the plant to yellow and die.  I have 2 tropic snow and a Marianne who are doing just fine and I water them all at the same time.  I was advised to leave the water out overnight before watering and have done this for about 6 months.  Any advice would be GREATLY appreciated!

Answer
Hi Tricia,

Yellow leaves are a generic symptom. That means that they have multiple causes rather than a single cause. Those causes include improper light and improper watering. (BTW, for me to see a photo, you have to email it directly to my address below.)

If you have your Dieffenbachias more than 6 feet away from the south-facing windows, then that may not be quite enough light to keep them thriving. On the other hand, if they are right in front of the window, the direct sun may be too much for them. Keep the light as bright as possible while still protecting them from the sun shining directly on their leaves for more than an hour or so each day.

Good that you did not repot your Triumph because that would make watering more difficult. It is very unlikely that all of your Dieffenbachias will need water at the same time and on the same schedule. I know that is more convenient for you, but that is not best for your plants. I suspect this may be where you are going wrong.

If a Dieffenbachia is in a small pot (6" or less), then water it thoroughly whenever the top inch of soil is dry to the touch. For larger plants, allow the top quarter of the soil to dry out between waterings. How frequent that is will depend on the amount of light, temperature, pot size, age of plant, root system, and humidity. That is why I cannot tell you how often to water and why it is unlikely that all of your plants will need water at the same time. If in doubt about when to water, it is best to err on the side of dryness.

Unless you are using heavily chlorinated pool water for your plants, there is no benefit to exposing the water to air overnight. However, if your tap water is hard, then use filtered, distilled or rainwater.

It is quite normal for new plants to lose some older leaves right after they are relocated to a new environment. In addition, it is normal for them to lose some older leaves as they age and add new ones on top. In time, almost all Dieffenbachias become tall and leggy. The solution is to prune them back as needed.

Please let me know if any of this is unclear or if you have any additional questions. If you would like to e-mail me some photos, I may be able to provide some additional insights.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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