Hi Luis,
I am not sure how long they take to fruit. In this part of China, the bananas go dormant for maybe 4 months each year in winter. During this season it is very dry, cool (near freezing at night) and DUSTY !!! The plant leaves and the entire city got coated in a fresh layer of dust each day. Certainly not optimal conditions.
The da jiao fruit looked like Orinoco so I really thought I was going to be disappointed with the taste. But when I ate one, it was soft and sweet. I also bought the Thai banana (namwa) and preferred the da jiao. I bought both from this roadside vendor and as you can see they are optimally ripe. Da jiao is in the bottom left.
I think this is a flowering da jiao:
In Southern China, bananas grow like weeds and I doubt many farmers know how many days until harvest. They just know that eventually it will happen.
I even found some bigger plants....
Erik