Epimedium sempervirens 'Okuda's White'
10th May 2009
A recently introduced name, I have yet to see it in flower.
1st May 2010
References:
Barker, David G. - Epimedium and other herbaceous Berberidaceae, Hardy Plant Society, 1997
Stearn, William T. - Epimedium, 2002.