I am drinking beer now and don't have reserch paper with me now
Small ume is most likely " koshu koume" Koshu is name of place, today koshu is yamanashi prfecture west of Tokyo. Koume mean small ume.
Nanko is very popular for umeboshi. Nanko are growing Wakayama prefecture. Nanko is large fruit.
kaga, shiro kaga , mochida was poplar. If you live west coast, you can buy ume at store. I have a friend who run Japanese restaran at Thousand Oak, Cal she buy ume in box.
ume of 5 to 6 years old from seedling can produce fruit. if you feed then heavely.
I have reserch paper which conducted 1930 by Japanese resercher. it has very detail descreption of prunus mume.
I can't grow ume where I am now , I gave ume seedling 5~ 6 years ago to a friend who live in South Carolina, his ume is producing fruit now.
Did I answer to your question? Do you have any other question?
Thank you for beautifull photo. I am new to this website. but I kenw Scott past 6 ~7 yaers and Herb.
You are helping others so I help you. I am not trained to write English but well trained in my trade.