When they flower you will be able to tell them apart with ease.
Helleborus foetidus tends to seed around especially when it is happy..ie. in the shade.
Helleborus x hybridus can become an obsession...collecting different colours from white, yellow, pink, red, deep plum. Spotted. Single and double flowers.
They look stunning when floated in a glass bowl of water.
https://www.google.co.uk/searc...
There are other Helleborus I love...just for the interesting leaf shape.eg Helleborus multifidus subsp hercegovinus
http://www.louistheplantgeek.c...