Lenten Rose (Helleborus X Hybridus) is quite often white. The easiest way to differentiate this from a Christmas Rose (H. niger) is the foliage. Once you have seen both, you can never mix them up.

Lenten Rose leaves generally have 7-9 leaflets. The center 3 generally undivided and lightly toothed, and all arise from a nearly central point like a lupine leaf.

Christmas Rose leaves generally branch off a curved stem section, somewhat like a maidenhair fern leaf though not as extreme. They also have a much heavier texture than the X hybridus.

George

One other obvious distinguishing feature is the flower stalks themselves. H. niger will generally flower at 6-9 inches and will usually only have one flower (sometimes two) per stalk. Also, the bracts (leaf-like structures on the flower stalk) are small and inconspicuous compared to H x hybridus.