Which one of these is the hardier elder? Every time I buy a magazine, they say one or the other is hardier. Please advise.
Not sure, most sources I read say both are actually sambucus nigra and hardy to zone 4.
I do have another cultivar of sambucus nigra, sambucus nigra 'madonna' and it does suffer winter kill. It was two feet high last summer and died back to about a foot. However, seeing that it is basically newly planted, this might have affected it as well.
It's supposedly quick growing, so once it gets an established root system it will be interesting to see how big it gets in one summer.
I'm not sure about hardiness, but 'Black Beauty' is a much nicer shrub than Guicho Purple. Guicho Purple greens up during the summer. The leaves on Black Beauty are much, much darker and stay that way. Madonna has not fared well here, usually suffering severely from winter die back. Both Guicho purple and Black Beauty seem stronger. In fact, the Black Beauty planted last November (replacement for Guicho) as a companion for a golden-leaf elder is already leafing out, much ahead of other shrubs in the garden.