I was overcome with curiosity because I've never heard of the Heartnut tree, so I looked it up. I'm glad I did because it is an interesting tree that apparently has a wide distribution and according to one of the sites I was on it has reportedly withstood temps down to -40* f. Pretty good for a nut tree that seems to be quite productive too. I would like to plant one here. Thanks for bringing my attention to it. Here's the site I was on if you're interested: http://www.songonline.ca/library/articles/japanesewalnut_1930.htm
I found that site also. I like the fact of being cold hardy and more disease resistant than the english walnut.
When I started I was more interested in the english walnut and being a member of the arbor day foundation where you can buy the english tree I asked them a bunch of questions about that tree and a nice gentleman referred me to oikos tree farm.com where they have a very nice selection of trees.