On a visit to Japan, ( outer Tokyo area ) I saw various Citrus trees in home gardens, and young trees at plant nurseries.
Specialty Citrus fruit was sometimes seen in supermarkets, i.e. unusual Japanese varieties.
I am wondering if there are any Citrus collectors / hobbyists in Japan ?
Any Citrus Forums in Japan ?
It is not hard to find webpages for Citrus farmers growing less common types,
but that is about as far as I have got.
Mature Flying Dragon tree/budwood
In my climate, ungrafted FD seedlings fruit in about 5 years. Also produce some interesting Off Types.
You can speed up their growth by extra heat, shortening the dormancy period.