The classic large-flowered hybrid clematis that are icons of British gardens are also perfectly hardy and long-lived throughout USDA Hardiness Zones 4 through 8 in the East and 4 through 9 in the West. But most won't grow well through the hot, dry summers where I live in southern California (zone 10). However, I've discovered techniques that allow gardeners like me to enjoy these spectacular flowers.
I surveyed clematis experts both close to home and in Florida to find which varieties thrive in their areas and how to grow them. While zone 10 regions of both states are notable for their mild winters, their climates are vastly different in other ways. Nevertheless, gardeners in both regions recommend planting the pink 'Comtesse de Bouchaud'. Other recommended varieties include 'Ernest Markham' (red) and 'Duchess of Edinburgh' (white).
In Florida, plant in containers rather than in soil. With roots more exposed, clematis experience more "winter chill" and so are more likely to bloom the following spring. Use a 15- to 20-inch pot filled with a 50-50 mixture of peat-based commercial potting soil and washed builder's sand.
In southern California, clematis grow best in the ground in well-drained soil. Set the crown at least 2 inches below the soil surface, and cover the soil with bark mulch. Keep the mulch away from the stems to minimize the chance of rot. All the Florida varieties grow well here, as well as 'Marie Boisselot' (white), 'Victoria' (lavender), and 'Ville de Lyon' (carmine red).
Wherever you grow clematis, stake young plants until they're established. Keep the soil moist but not soggy, and don't be alarmed if some leaves brown during hot spells. Ignore them, or pick them off, but don't cut the stems. New leaves will grow once temperatures drop.
For information on clematis, contact the American Clematis Society, (949) 653-0907, www.clematis.org.
Karen Dardick lives in Los Angeles and is a regular contributor to National Gardening.