First of all, it's not really a rose. Helleborus niger is now put in its own family (Helleboraceae), although still allied with the buttercups. Although seemingly innocent with that ghostly whiteness, it is quite poisonous despite being part of the European materia medica for hundreds of years: we do not recommend sampling any part of this! Nevertheless, if you have a European friend, you are very likely to have received a Christmas Card featuring this beloved wildflower from the Eastern Alps. It grows through much of the higher elevations of the Balkans, and has been cultivated for hundreds of years in Europe for its precocious bloom. There are some forms that will reliably begin to bloom in late Autumn in Colorado. Mine usually don't start blooming until early in the New Year: it depends what sort of winter we have. With snow in the offing, we may have to wait for 2013 to see these out at the Botanic Gardens outdoors, but you can find some lovely specimens in the Orangerie (these are being produced on a huge scale in recent years as Christmas decoration you can save and then plant outdoors!). I believe there are a few garden centers in Denver that are selling these as we speak (Since I know you are wondering, its O'Tooles--but I would call ahead to make sure they still have some).
Here is a glorious colony growing just West of our Administration building. I took that picture last February: they do bloom for many months! A good reason to plant some in a shady spot at your house.
For a dramatic contrast, this is the "Lenten Rose"--which suggests that it blooms in March and April, around the time of lent. It's true that this does bloom well into the spring, but I have had lenten roses start blooming in January as well. Their deep plum, almost black flowers are a wonderful contrast to the virginal white of the Christmas rose--and they will overlap in blooming for some time. An amazing revolution has occurred the last twenty years with hybridizing lenten roses: you can now find them in a fantastic range of attractive colors from nearly yellow to rose pinks and almost reds: there are wonderfully dotted forms, and some with flowers that are almost upfacing: there are gardens in Europe and the coasts of the US that boast hundreds of these new hybrids. These gardens are as lovely to visit in midwinter as in the summer months...we're way behind in Denver on the Hellebore front! Time to prepare some more shady beds!
These are growing in a half dozen gardens at DBG: do take a stroll around over the next month and see how many of these paradoxical roses you can find. A little like looking for Waldo or Easter eggs--only for us plant nuts! Merry Christmas and Happy Holidays!