Q.How do I prune my hydrangea and budleia? Do I need to dead head petunias?
Budleia has not flowered this summer.
Buddleia is pruned in the South either late fall or early spring. In snowy weather areas, the plant dies back to 9 inches or so depending on how cold your region gets. Pruning back is done while it is dormant. Normally, I recommend dead=heading to keep it blooming and make the shrub, in my opinion, look better. Did it grow well this year? I've never heard of a butterfly bush not blooming. Have you looked for aphids or other pests at the branch tips where blooms would be expected? Is it getting enough sun or have other shrubs and trees grown enough to shade it now? Hydrangea pruning depends on the type of hydrangea you have. You can send a long a picture if you didn't keep the plant tag. Links below discuss care of these 2 plants.
https://www.gardeningknowhow.com/ornamental/shrubs/butterfly-bush/problems-with-butterfly-bush.htm
https://www.gardeningknowhow.com/ornamental/shrubs/butterfly-bush/butterfly-bush-not-blooming.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm