Thanks for your question.

As you probably know, “dumb cane” is another name for a plant in the genus Dieffenbachia. In your situation, it appears that the main issue is that the leaves on the plant appear yellow and dry. I assume this is what you term “bad leaves”. Before directly addressing what might be wrong with your plant, here is some general background information about this type of plant:

https://www.youtube.com/watch?v=R5gGFLrssMs

https://homegarden.cahnr.uconn.edu/factsheets/dieffenbachia/

https://extension.illinois.edu/houseplants/dieffenbachia

Your plant is showing clear signs of severe stress. However, I believe with persistence and patience it’s very recoverable. Here are my thoughts:

1). The fact that the plant goes through periods of looking fine and then developing stressed leaves implies that the root system is functioning. This is a good indicator that the plant is still fundamentally healthy.

2). I cannot tell from your picture if there are drainage holes in the pot. It appears that the pot is on top of some type of dish. This would suggest that the pot has drain holes. If by chance drain holes are absent in the existing pot, you should remove the plant and soil from the pot and transplant things into one with drain holes.

3). My initial impression was that you were overwatering the plant. I’ve decided against this possibility since overwatered cane plants usually show mushy stems and soft yellow leaves. These two characteristics don’t seem to be present. The stems look firm and healthy green. To confirm my conclusion that overwatering is not present, take a good, long smell of the soil. Put your nose right down to the soil’s surface! If you detect a foul, almost obnoxious, odor this would be a sign of overwatering that has led to rotting soil. If there is an “earthy” smell, this would be inconsistent with overwatering.

4). I suspect that under watering has occurred and/or your watering schedule is inconsistent. For example, between waterings does the soil become very dry? In other words, do you follow a regular and consistent watering schedule? Note the yellowing leaves appear to be thin and papery. This is an indicator that the plant has experienced periods of extended dryness. The sharp, dry brown leaf tips also point to irregular or insufficient watering. Cane plants do not like to be exposed to low humidity conditions such as exist in Minnesota rooms during this time of the year (late fall, early winter 2025). If this plant is near a fan or warm air heating vent, low humidity could occur.

5). Some of the characteristics seen in your plant can occur when it is exposed to direct light that might be too intense.

Going forward, I suggest the following:

1). The most important thing is to develop a regular watering schedule. Water thoroughly until water drains from the pot’s drainage holes. Then do not water again until the top two or three inches of soil are completely dry. This is best determined by inserting your index finger into the soil to the second joint. If the soil to this depth feels damp, don’t water. If it feels bone dry, water. Typically, this would put you into a seven to ten day cycle.

2). Try to increase humidity around the plant. Put the pot on a tray containing pebbles/marbles covered with water. Ideally, aim for a surrounding humidity between 40% to 60%.

3). Do not place the plant in a location that is in direct sun. Indirect sunlight would be preferable.

4. If yellow or brown leaves appear, remove and discard them. These leaves will not recover. If a leaf looks nice and green but has a brown tip, just snip this tip off and discard it.

See the following for further information on these and related points:

https://www.youtube.com/watch?v=s9kxpFBkVFE&t=85s

https://gardeningsolutions.ifas.ufl.edu/plants/houseplants/dieffenbachia/

https://www.thespruce.com/dumb-cane-dieffenbachia-definition-1902751

Good luck. Please get back to us if you have any additional, related questions. Thanks for using our forum.