Garden catalogue descriptions of plants that bloom all summer often seem too good to be true. Some gardeners have trouble getting their clematis to bloom at all because they don't realise that different groups of clematis require different pruning practices. Cooperative extension horticulturalists live in the real world, however, and confirm that some clematis cultivars can bloom all summer. Take care in choosing clematis for your garden, treat them right and you, too, can enjoy these vines' summer flowers.
Many of the summer-blooming clematis are in the Group 3 pruning category, which flower on new wood, according to University of Illinois Extension's Sandra Mason. Mason notes there are many vigorous Clematis viticella cultivars, and that 'Madame Julia Correvon' will produce her red flowers all summer long. Among the other distinguished varieties are the purple-pink to reddish 'Ernest Markham', blue 'Lady Betty Balfour' and red 'Ville de Lyon'.
Clematis x Jackmannii
The Clematis x jackmannii hybrids also bloom all summer on new growth, according to University of Arkansas Cooperative Extension's Janet Carson. She singles out cultivars 'Alba', 'Comtesse de Bouchard' and 'Star of India'; these plants have large white, pink and purple flowers, respectively.
Durand clematis (Clematis durandii) also bloom on new wood, but unlike most clematis they are more compact plants, described as either nonvining or less vigorous, with blue flowers that can range from lavender to indigo. Iowa State Extension's Cindy Hayes notes that the attractive blooms begin in early summer and can continue until frost. Most summer-flowering clematis are hardy to at least U.S. Department of Agriculture zone 6.
Another compact clematis, the native Clematis texenis, has scarlet-red bell-shaped flowers and dense foliage. The Ladybird Wildflower Center notes that it is more herbaceous than woody, and climbs a maximum of 9 feet. North Carolina State University Extension's Erv Evans says it blooms on new growth from summer until frost. Like other summer bloomers, C. texensis needs a sunny exposure.