Evan, as you know Gubijin is a pseudata. Not pseudacorus. Cross with a white ensata, I'm not sure which one. Gubijin is fertile, yes, but is it invasive? Gubijin is a cross between a pseudacorus and a Japanese. Any of it's offspring are crosses between Gubijin and a Japanese, so now we have 2 Japanese in the mix with one pseudacorus. I don't know of any Japanese that are invasive here, so I truly doubt Gubijin is invasive.
I have had a Gubijin for a few years and they do set quite a few seeds. They don't seem to pollinate easily by themselves, and the problem here is they don't bloom with the Japanese. The Japanese bloom later. I now have pollinated a few by having a friend south of me sending pollen.
So, I just don't see Gubijin being invasive. They don't self cross.
I am not aware of an other fertile pseudatas, and Mr Shimizu tested thousands of pseudatas for fertility for years before finding Gubijin.
