I haven't had time to check any other plant catalogs and see if it's spelled differently. I'll do that after I get in from classes later on this evening. I entered that name because that is the name on the ID plate at the base of the plant. Maybe thd folks at Longwood Gardens misspelled the name?
I don't doubt that you copied it correctly from the nameplate - but they could be wrong. Some of these quirky cultivar names can have different spelling variations. But Tony Avent at PDN is usually pretty good with details. I have this same plant growing in my back yard so I am going with the spelling on my tag. :-)