When to stain in MD - pollen starting

Hello,

I have a PT deck built 8/2018 that has one coat of oil-based semi- transparent Armstrong Clark on it and has multiple unstained deck boards that were replaced in DEC as well as vertical framing that I never stained last Fall.  Question is should I stain now mid-March as trees are just starting to bud and pollen is starting or wait until MAY/JUN/JUL or SEP/OCT/NOV?

Thanks for the advice.