I'm going to buy a clematis. I believe they like sun on the foliage, but shaded roots. What does shaded roots actually mean. Do I need to plant the clematis under a leafy tree or a wall, then train it out to where I want it? Would it be OK to plant it in a trough in full sun, and plant other plants (e.g. violas) on top, or cover the soil with gravel, or rocks?
Maybe a trough isn't the place for a clematis and I should consider a passionflower instead?