What do you recommend for timber frame beams?

Hi,
I live in northern Alberta, Canada. I am in the process of installing timber frame decks. Front entrance deck is north facing and back deck 20X30 is south facing. As you would know, I have huge beams, and they are cut from west coast Douglas Fir. This is a pretty pricey project so I really want to protect these beams right the first time. Mold doesn’t seem to be an issue in our fairly dry climate up here, but thick beams like this are installed still green and so staining is a bit different than 1 inch deck boards (or so I have learned through online reading this past month). What stain do you recommend for a project like this?