Nothing now.....you just need to let the excess fertilization work its way through the soil and the plant's system, which it will in time.

I'd be very interested to know what type of clematis produces that long a bloom season. Even in my very mild and clematis-suited climate, I know of NO vines that will continue to bloom over that very extended period. A few will offer periodic rebloom after the primary bloom flush but never continuous bloom from early spring through late fall. Also, it is often cautioned NOT to fertilize clematis while in bloom so as to avoid the premature halt in blooming this practice often encourages.

Thanks. I cannot remember the name of the variety but I recall I picked it because it said it bloomed early summer through fall. I got it at Lowes and they only carry a handful of varieties. I do not prune it down in the Fall and it actually starts getting buds on the old growth in February if you can believe it.