The Princess Diana Clematis received The Royal Horticultural Society, Award of Garden Merit (AGM). The blossoms resemble little bells or lilies and often tilt downward with their shy beauty. Hardy to -30F (-34.4C) and extremely heat tolerant, it is a great choice for just about any garden. Plant in a sunny location and prune each spring before new growth starts. It belongs to the Group 3 clematis, summer/fall bloomers. This dainty vine is tough, hardy and relatively pest-free.