Answer: The dappled willow can grow quite large so many people do routinely prune it back very hard in early spring before it starts to grow for the season. Otherwise, you can prune selectively during the spring and summer and thin out some of the longest branches by removing them at the base. This will control the overall size and silhouette somewhat but still allow it to take on its naturally billowy shape.
Clematis usually take several years to become rooted and established and then begin to grow and bloom normally. The old saying is first year they sleep, second year they creep, third year they leap. It is better to underfertilize than to overfertilize resulting in excessive weak growth. So as long as it seems healthy but slow I would not recommend more.
A top dressing of good quality compost in spring, an application of general purpose granular or slow release fertilizer with an analysis of 10-10-10 per the label instructions and an ongoing layer of organic mulch should be adequate. For a more detailed fertilizer recommendation you would need to run some soil tests and then fertilize as indicated by the results. YOur local county extension should be able to help you with the testing and interpreting the results.
I hope this helps.
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