Talking about Clematis 'Toki', NHDirtlover wrote:

Reliable clematis in zone 5b
..N.H. . No pruning or winter protection needed. Lots of loam, sun and a shallow rooted ground cover (Lysimachia)
outstanding.

Talking about Clematis 'Ville de Lyon', Trish wrote:

A good Clematis to grow in the north, * 'Ville de Lyon', was noted for its 5-inch-diameter brilliant crimson flowers from late May to July and again in September on vigorous, 7-foot-tall vines. The variety showed no signs of wilt.

Talking about Clematis (Clematis viticella 'Etoile Violette'), Trish wrote:

A good variety of Clematis to grow in the north, C. viticella 'Etoile Violette', produced 3-inch-diameter violet flowers that began blooming in late June and continued until August. It also had 80 to 100 percent coverage during peak bloom time and no clematis wilt during the six-year study period.

Talking about Clematis (Clematis durandii), Trish wrote:

A good Clematis to grow in the north, Clematis durandii, is a rambler rather than a climber and is best grown through a shrub or tree, such as arborvitae. In the study, it bloomed abundantly from June through July with 5-inch-diameter indigo flowers; it had some dieback in one year from clematis wilt.

Talking about Clematis 'Comtesse de Bouchaud', Trish wrote:

A good Clematis to grow in the north, * 'Comtesse de Bouchard', a vigorous climber, reaches more than 8 feet tall in one year. It flowered from mid-June to late August with 5-inch-diameter mauve-pink flowers. During its peak bloom period, flowers covered 80 to 100 percent of the plant. Bloom repeats in October. Comtesse de Bouchard plants had little winter dieback but, in two of the study years, had some dieback from clematis wilt.