I'm not sure, but if no one chimes in with an answer you may want to contact your county extension agent and ask him/her. I'd be interested to know too.

You can always check on the conifers forum but what I was told was that it's the climate. Firs don't like the midwest's hot, humid summers. I have had so so luck with the varieties I have tried, lost two out of four.

Balsam firs like being in the woods where it is damp and out of the wind. They also are not very full growing specimens. Red pine is similar: a northwoods tree that does not grow well in the open. Neither tree likes salt or air pollution.

White fir is not native, but will do fine in town if you can put up with the slow growth.