Also, let's be clear on what we are calling poplar. The "poplar" that is used in guitar manufacture, and what is typically marketed as "poplar" is tulip poplar, also called yellow poplar, Liriodendron Tulipfera. Not in the poplar family at all, yet that is what is generally meant when we refer to poplar, at least in the US. It gets a little less clear the further north you go, as you get into the growing range of the true poplars, like aspen, balsam poplar, etc. The top of the guitar linked to earlier, is of the latter variety, and is much more likely to exhibit figure than yellow poplar. Yellow poplar is a bit denser, and finer grained. Here is a bass I built out of it:
This is from a really nice piece, and all heartwood. Most of the stuff on the market is paler, with lots of white sapwood.
I happen to like yellow poplar quite well.
But again, if you are in Michigan, it is quite possible that aspen will be sold as poplar.