There is a slight sweet smell , the butterflies love it
The mildew looks bad but does not kill the plant . As far as spreading to other flowers I can not say for sure , I have not noticed it doing so but the nearby plants do not seem to be the mildew type.
Height depends on the year and rain amount . I do cut some down by about a foot 1st of July to stagger the blooms . You can also deadhead fading blooms to have re-flower till frost.
