sorry, don't know it.likely you alrdy found these through google:

http://www.chron.com/commons/persona.html?newspaperUserId=mycornerofkaty&plckController=PersonaBlog&plckScript=personaScript&plckElementId=personaDest&plckBlogId=Blog:mycornerofkaty&plckPersonaPage=PersonaBlog&plckCurrentPage=7

bigdipperfarm says z. 4-8:

http://www.bigdipperfarm.com/cgi-bin/cart/cart.pl?db=stuff.txt&method=all_words&search=Farfugium

best,
mindy

Here is a link that might be useful: big dipper farm

Please note that the patent for this plant indicates that it is a hybrid with "Ligularia hiberniflora as the female parent and an unnamed plant of Farfugium japonicum (syn. Ligularia tussilaginea)". The latter plant in my experience, is not very hardy, maybe to zone 7 or 8. I am not familiar with the female parent.

Appears to be an interesting plant, for those that are able to grow it.
I suspect that a Hardiness rating of Zone 4, is a result of someone's misunderstanding or a vivid imagination!

Ligularia hiberniflora is endemic to the neighboring Japanese Islands of Yakushima and Tanegashima, where it is companion to Ligularia tussilaginea.
As a result of several high mountains on Yakushima, the climate varies from sub-tropical to sub-alpine, but as we have determined from growing Ligularia tussilaginea, it would not be reliably hardy below Zone 7. In fact, I make it a practice to protect my several different cultivars, when the temperature is predicted to fall below 10°F.

Let us know how your sun-burned patients progress!
In the meantime, I shall be on the look-out for them to appear at my local nurseries, who will sometimes offer something out of the ordinary!

OT...
I am of the old, old school and still prefer the familiar Genus designation of Ligularia!
After all, the change to Farfugium was ignored by the scientific community for almost 70 years, why the urge now to recognize it?

I have it in my yard, bought it last year and put in a wooded area. I think I may have watered it times, it bloomed for a long time and tripled in size in the first year.