Yes they basically are.

From Wikipedia - One of the species, the cinnamon fern (Osmundastrum cinnamomeum) forms huge clonal colonies in swamp areas. These ferns form massive rootstocks with densely-matted, wiry roots. This root mass is an excellent substrate for many epiphytal plants. They are often harvested as osmundine and used horticulturally, especially in propagating and growing orchids.

It's sort of considered old world potting medium. You won't find people growing in straight osmunda. doesn't mean they don't but I've never known anyone to. I did once and found it rather frustrating to work with and it tends to hold a lot if water. Some nurseries will use it as a part of their potting mix, but bark and sphagnum moss are far more common.

I use it mixed with sphag. Helps keep it from packing and lasts a long time. Its excellent for drainage.

Jane

Jane I'm curious, what percent?

Might be the same North of the equator, not so here and in NZ where the cut up trunks of tree fern makes a good mount.

I use it along with sphagnum for mounting on cork or other mounts. I firmly place it between the plant and the cork.

Thanks very much for the info everyone.Whenever I repot my orchids now I use a mixture of aliflor and tree fern as my potting medium.It seems to last for a few years without me having to repot so often.

Allymarie

Yes, it does seem to last forever.

Terpguy, I like mixing it with sphag when I pot Phals or Oncids which like to be kept a bit damp. My guess (I just eyeball) is about 10%. I mix it into dampened sphag. Keeps the sphag open.

Jane

Hi
Have often used tree fern insted of cork over the years
heck of a problem to transplant you have to butcher to get it out . I recently started a "Tree fern " forest okay not so much a forest as a group lol Have 5 species so far and can't wait to try various orchids on the living plants Anybody ever try that ? I suspect the tomentose fiber will hold too much water and they do shed but will be a fun experiment?? Been searching for the Florida native specie but have been unable to find it . Only specie native to the continental US . gary

We grew in 100% osmunda when I was a kid. We called it "fiber." It worked very well.