I used to have a beautiful hybrid clematis on the trellis in the front courtyard. It died and was replaced with a smaller native Texas clematis cultivar I purchased at the Wildflower Center sale. When it flowered I was disappointed in its color and its performance. Last fall I put it on a drip, added slow release fertilizer and voila. It did the trick.
Right now it is festooned with seed heads and more new flowers are appearing. Although not quite the purple I had hoped for they are much improved. All the plant needed was a little help.