Clematis 'Multi-Blue' has large dark blue to purple flowers which are double, made even showier by the frilly white tipped stamenoids. Blooms for an extended time starting in June and the flowers persist longer because they're double and therefore sterile.
PRN Preferred: Large long blooming flowers. Once the petals fall the anthers remain for added interest.
USDA Hardiness Zone
Clematis Multi-Blue #2 Trellised (dark blue to purple)