Clematis positively exploded this year! The cooler ground was surely to blame. Make sure the roots of your Clematis are shaded (kept cool) and the foliage is in the sun. If you can accommodate this, you will have very happy plants!
Clematis Duchess Of Edinburgh: Duchess of Edinburgh graces its vine with fine lovely double white petals. The sparkling white blossoms open in May and June, then reappear in September. Flowers are 4-6" across.