Of all the cordage materials I have found and read about in books I have never seen this mentioned but I think may have possibilities.
I grow okra every year in my garden and when the stalks dry up and die in fall and winter the bark is very fibrous. I haven't spliced a bunch of it together and tried to make a rope but I think it could be done. I also don't think it would be strong enough for a bowstring or anything, but as a common string I think it would work good. It is strong and long fibers.
I just thought it was interesting when I noticed this and have never seen any books or online stuff talk about okra for cordage but I think it would work pretty well.