Very interesting article.
I agree on trial and error for zones. I have some Agastache that I grow from seed that are listed as zone 7. Most (not all) of them come back for me. At least for the three years counting now. I also bought a coreopsis, I think it is Garnet, and it was listed as zone 7. It has done fine for me for two winters now. Pink Muhly grass also does fine for me. It just does not get as big as it does for those further south.
Yet I have other stuff that is listed as zone 5 and I cannot get them to overwinter ever! Guara and Salvia greggii come to mind. And Caryopteris. But there are others too.
I try to always look at a plant's demise as an opportunity to try something new in its place. Heaven knows I ALWAYS have something new to slot in due to my PBA (plant buying addiction)!
