General Characteristics: Clematis may be planted and trained to cover walls, trellis, posts, fences, arbors or to cover rocky sites. It will need support. Prefers a rich, well-drained soil with a pH of 5.6-6.5. Clematis do best in neutral or slightly alkaline soils, but they are somewhat adaptable. If you have very acid soil, try to add some calcium when you plant. If you want to grow really good clematis you should incorporate a little lime in the planting holes. Roots should be planted in a cool moist environment, while the vine itself should be in the sun. Root area should be protected. They require 1" of water a week. 'Rouge Cardinal' produces masses of gorgeous crimson flowers from mid-summer to early autumn. Careful training is required as the plant tends to be quite floppy.