Botanical Sites of interest near Billings, Montana for trip planned in summer

Submitted by New River Valley on Fri, 11/21/2014 - 11:39

I plan to visit friends who have recently moved to Billings, Montana.  I would like to rent a car and do some plant exploration in the summer.  Where is the best place to go?  When is the best time to go?

Beth Umberger Zone 6 in the mountains of SW Virginia.