Can anybody tell me what's wrong with my Australian fern?

Ferns generally like very rich soil high in organic matter. I use 1/2 potting soil and 1/2 peat moss.
They generally like to be moist, partially to fully shaded and 65-85% humidity. How is your humidity? What type of soil?
Browning like this often means improper moisture.
More info as to where you have them might help somebody diagnose your issues even more then me.

It would be so interesting to get a handful of answers for this question. @Carter has such a diverse knowledge, maybe he has experience with this plant. I will throw out a guess and it may prompt some to correct me and get you some ideas.

Are you sure it is not normal behavior, as seasons change?

It is unique to see plants display the beginning of browning from the base of a leaf instead of the tip. When I looked around the internet at your fern for you, I did see many growing in their natural habitat that had similar browning. So, I wonder if it's just the way they purge old leaves. I also read that this plant is being hit by disease that is new, in Australia. I could not find an image of spider mite damage on this tree fern, but since I am only able to GUESS, the damage looks a bit like spider mite damage, so I would at least eliminate that. If your plants are acclimating to a fairly new environment, are they in enough shade. What is growing above them. What is that root system like. I have a huge cedar tree who's roots not only discourage growth of plants I try to grow nearby, it is also killing my blacktop and trying to choke out my plumbing.


So I am no help at all, my hope is at least people may come and dispute my guesses and you can at least eliminate a few concerns.

I would love to have a couple of your trees, They are beautiful. Good luck.

Thanks for your answers. I've posted 3 large ferns I have in my backyard to show I've kind of got the hang of them...these are large and lovely. Same soil and sun/shade ration. I live in Santa Barbara in zone 9-10. Thanks for your feedback and I hope others may contribute.

My first impression was a moisture/humidity issue as Bill mentioned, but if your others aren't having the same problem, I think that would rule that out. You're others look like they get some sun. Does this one get any direct sun? If not, maybe that could be the issue? Not enough sun *could* possible make the foliage die back in patchy areas like that, I suppose. That's kind of a guess, tho. I'm really not sure.