I think your plant might be Cezanne, not Lezanne.
http://www.clematis.hull.ac.uk/new-clemdetail.cfm?dbkey=2970

Here is Twilight
http://www.clematis.hull.ac.uk/new-clemdetail.cfm?dbkey=31

It's somewhat of a controversial subject, but I don't believe deadheading helps. Some people think that it helps.
Clematis like to be in soils that are evenly moist - not too wet, not dry.

Both are early flowering, so pruning it optional. However, you will want to prune it for the first 2 years about a foot from the ground. You might also want to pinch the vines once in spring to encourage branching. After the first 2 years, you can prune when it gets unruly or prune just the top foot or so, cut off the dead petioles to rearrange the vines.