Answer: Based on your description, I think your clematis is suffering from transplant shock rather than the dreaded clematis wilt. (The wilt is a fungal stem rot and leaf spot which causes whole sections of the vine to collapse and turn black in a matter of days. If you suspect wilt, cut away the blackened sections immediately and destroy them.)
The best times to transplant clematis are fall, late winter and very early spring, taking as many roots as possible and cutting back the top to compensate for the lost roots. The first year, to help the plant reestablish, it is a good idea to apply plenty of compost or well rotted manure or a well-balanced fertilizer such as 10-10-10 in addition to ensuring the plant receives plenty of water -- roughly an inch a week.
"Nelly Moser" does best in morning sun or part shade, primarily because the colors tend to fade in full sun. Ideally, too, like all clematis it needs a cool and moist yet well drained root run. In addition, the soil pH should be about neutral (ie near pH of 7) and a mulch is a good idea.
At this point, trim away and remove any dead stems and leaves. Keep the plant mulched and well watered until winter sets in -- if in doubt, check the soil with your finger. Early next spring (February or March) remove any very weak stems and cut the plant back to strong buds at about a foot from the ground. Fertilize it and/or apply compost, make sure it is well watered, and you should see blooms on the new stems originating from this year's growth. If the vine is well enough established, it may also bloom a second time in late summer on new growth formed that summer.
Good luck with your clematis!
Q&A Library Searching Tips