These plants come from one I bought over 40 years ago. I don’t know what it ‘s called. Recently there have been a plethora of yellow leaves. This has never happened before. Your thoughts .
Thank you for contacting the Toronto Master Gardeners concerning your Thaumatophyllum bipinnatifidum, formerly Philodendron bipinnatifidum (Tree Philodendron).
These large plants are native to the tropical regions of South America. They grow best in a warm, humid environment in loamy, moist but well-draining soil, in medium to bright indirect light. It appears that your plant is quite close to a window. Is there a heating vent near by? Their yellow leaves could be your plant telling you that it requires more humidity.
In most cases, yellow leaves are a result of either over — or under — watering. How often are you watering your plant? Typically, you should not have to water more than once a week, and only once the top two inches of soil are dry.
Has your plant recently been fertilized? Most houseplants benefit from being fertilized once a month, from spring to fall, with a regular 10-10-10 fertilizer. Make sure to follow instructions on the package for dilution.
For more information on growing this lovely houseplant you may be interested in the following links: Philodendron bipinnatifidum, Thaumatophyllum bipinnatifidum, and Tree Philodendron.