There's clearly 2 types of poplar being talked about in this thread and most people don't know the difference. If its quaking aspen poplar, the deer, grouse and turkey love it and it will get thicker than hell after you cut it as said in previous posts because it sends up suckers off the root system and is damn near impossible to get rid of. But you won't get two squirts of piss from it if you try to sell it and that is if you can find somebody to take it. If you find somebody that will pay premium money for it, let me know cause I got some more they can buy. Some people use it in interior applications because it has no rot resistance but its a bitch to work with because it warps and splits so much. Most people that have used it put it up green. One application is match stick manufacturing if that tells you anything about its burning properties.
Tulip or yellow poplar, on the other hand, is a semi valuable hardwood has good woodworking properties and is used in many applications. Some regions last fall it wasn't too far below maple in price. Not as valuable to wildlife as quaking aspen but definitely not worthless especially if you are managing your timber with the expectation of some sort of financial return.