Answer: Besides pinching for bushiness or pruning out winter damage, the vines are likely to need only an occasional thinning out of old unsightly and thick vines.
You do not mention how old the clematis is. If it is quite young, you can pinch off the top buds on the growing sprouts to encourage them to branch up into more vines and thus make a bushier plant.
Also, it is good to know whether you have a clematis that blooms on "old" or "new" wood. Generally, northern clematis, such as those in the Jackman group of hybrids, bloom on new wood. Sometimes these vines will be winterkilled right to the ground. For this reason most clematis sold in the north blooms on new wood. This variety will growup and bloom on an entirely new vine each year!
If by chance your clematis flowers on old wood, prune dead and broken growth in the spring. After flowering, a portion of old shoots should be cut back severely. Clematis do enjoy a rich, humusy soil. Give them lots of organic matter such as compost or composted manure. Clematis enjoy having their heads in the sun and their feet in the shade, so mulch is helpful to keep roots cool and to keep competing weeds at bay.
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