I wouldn't leave it natural it's a softer wood it doesn't have natural protections like cedar

Definitely need to apply a finish as Rockin Fine states and I was remiss in mentioning that.

It's used around here as siding with good (not great) rot resistance. The Town salt barn was sided in unfinished hemlock 25 years ago and still looks ok.

Thanks for the feedback. Will a clear stain be enough protection?

if you don't to change the color much use a Dalys ship and shore sealer you need to apply it very couple of years. if you want something longer term stain. there are products out there that claim that wood will stay sealed longer I have never tried them.