[Spectian]

I've kept java fern for decades and have never seen it do this before. What's up with the stems with three leaves showing up?

 

[Spectian]

The stems are originating from the rhizome.

 

[Neil8888]

Mine have done that after a few years before. The obvious cause is changes in the environment, but I have also read that they will do this suddenly if the larger, more established leaves are starting to die. I guess sections of leaves have individual life cycles, and when one is nearing the end, it will grow new sprouts to replace. Definitely not an expert in this area, but I remember reading that once and it seems to check out with what I have noticed with mine.