Clematis, Jackmanii Overview Category: Vines Common Name: Clematis, Jackmanii Botanical Name: Clematis 'Jackmanii' Sun Exposure: Full sun Height: 10 ft. Spread: Varies See notes | Back to vines Notes Flowers are dark velvet purple, 4". A profuse bloomer. Blooms June, July, August. Prune heavily early Spring to buds almost at ground level.