Here in the garden Clematis x cartmanii has been in flower for weeks. By and large I try to avoid hybrids but these flowers receive plenty of visits from bees, so it meets my approval! Its parents are two New Zealand species, Clematis marmoraria, from the Marble Mountains, and C. paniculata.
Clematis x cartwrightii. We grow two plants facing each other.
Stefen Hill, Daventry. 15 May, 2017