Yes. Cut them off just below the bloom. You'll have a much fresher looking
flower while allowing more energy to go into producing new blooms.
Deadheading can be done to just about any flower which leaves a dead bloom.
I even deadhead my gardenias. My baby Kleim's Hardy is just starting to
bloom now. Remember to water early in the morning so the water evaporates
from the leaves during the daylight hours. Zinnia's are prone to powdery
mildew fungus which comes from humid, wet conditions on the leaves. Hope
this helps.

Penny
"Michael Volow" wrote in message
...
With zinnias, do I deadhead all old withered bloom? Thanks in advance.