. Large-flowering Clematis Qlematis Paniculata LARGE-FLOWERING HARDY CLEMATIS. No other climbing plant equals in attractiveness the beautiful large-flowering Clematis. Their requirements are somewhat different from most other plants, and proper conditions must be given to secure satisfactory results. They need rich, deep soil, perfect drainage, abundance of water, and, most important of all, they should be planted with the crowns three inches beneath the surface of the soil. They seem to do best in a position where they will not be exposed to the full sun during the hot- test part of the day.