Did some more research and eventually discovered that G. homborniana is a very frequent synonym (one of a number of synonyms) for the widespread species, G. celibica.
To get them started and established, I've put my several small seedlings of it into a couple of tall tree pots to accommodate what appears to be going to be a rather long taproot.
The only other thing that would be helpful to know is what the cold tolerance of this species might be. Anyone on here have experience to know what kind of cold this species will tolerate?
TIA
Paul M.
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