Java Fern in substrate???

No. The roots can grow into it, but the rhizome (the thick tube-y part) cannot be, or the plant will rot.
 
I'm not sure if you can do that, but you might if you don't bury the rhizome into the gravel.
 
I don't see why setting it on the gravel, or planting it shallowly would be much different than setting it on a rock or driftwood.

I have several pieces in my tanks that I have planted like this. So far so good.
 
You can set it on the gravel, but if the rhizome gets buried, 95% of them die. The roots themselves are fine in substrate, but not the rhizome. Its different than on a rock, for instance, because the rhizome isn't covered with dirt on a rock.

rhiz.JPG
 
I have found that if you have really small peices and try to grow them bigger on the gravel that they tend to try to hug the surface and end up growing funny shaped and not straight across the gravel.

when I finally got some drift wood to put mine on some of the peices had grown like curly fries on the gravel and I wasn't able to put them on the wood.
 
What's even more radical looking is when you just let them grow into a free-floating ball that races around the tank on the current. (I don't suggest this since the leaves never grow to full length and the roots tend to give up and die about 2 or so inches out.)
 
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