Color: Blue Flower Size: 6-8″ (15-20cm) Flowering Period: May June & Sept Mature Height: 6-9′ (2-3m) Pruning Group: B1 Planting Aspect: Sun/ Partial Shade USDA Zone: 4 Suitable For Container: Yes Foliage: Deciduous Price Group: 2 About Blue Ravine A University of British Columbia, Botanical Garden introduction. The flowers 6-8″ (15-20cm) flowers are soft violet with slightly darker veins. Blooming time is May, June and Sept. Mature height 6-9′ (2-3m). Pruning group B1.