In different parts of the country 'Poplar' means different things, i.e. different species, which leads to a lot of confusion. Being in WV I'm assuming you have Tulip Poplar, same as we have here. In certain outdoor applications it is an excellent rot resistant wood. It has been used for hundreds of years for siding. Around here there are still some 100+ yr old barns and houses that still have the original Poplar siding, devoid of all paint years ago. If it is allowed to dry out it will hold up very well. It is not good for prolonged ground contact or areas that stay wet. Posts on a porch I'm not sure about. If you did something to the bottom I think it would be ok, maybe put it up on those little cast metal post pads. It won't last as a post in or on the ground for sure.