After a very cool spring, we had temps in the 90s for a couple of days. Every bloom on 4 clematis went completely limp when the hot sun hit them, not the vines nor the buds mind you, just the blooms. When the shade hit the blooms late afternoon, they perked up again and looked fine. There is no browning at all after 2 days of this behavior.

The sudden heat affected HF Young, Warsaw Nike, Madame Julia Correvon and an unknown G2 that is probably a seedling of Will Goodwin. Most of my other clematis receive at least the same amount of sun and more in many cases. Other clematis in the same areas were fine.

We have had good rains this year, and I gave every clematis a deep soaking before the heatwave hit, so it's not a moisutre issue. The plants had not shown any signs of stress prior to the heat wave.

HF Young and Warsaw Nike have been in the ground for 2-3 years, Madame Julia Correvon 3-4 years and the seedling for 6 or 7 years, so the age of the plant should not be a contributing factor. Why these clematis and not the other 30 clematis that were blooming?