Pulsatilla vulgaris 'Alba' |
The label says: Ferny foliage, large white flowers in spring followed by silky seedheads. According to the Royal Horticultural Society, Pulsatillas (external link) don't seem very fussy about soil and seem quite hardy but they do like to be well-drained and like full sun.
I already grow a red Pulsatilla (it's probably either Red Bells or Rubra - planted last year) and it's growing in a small border at the top of my garden which gets plenty of sun and good drainage. I plan to grow Alba in a terracotta pot for now with plenty of grit in the compost for drainage.