When I started looking at pics of Smallanthus uvedalia, I realized it looked very much like its South American cousin, Smallanthus sonchifolius (the yacón, a very edible tuber/root). And yes, S. uvedalia's roots are edible, too (kinda, anyway).

I grew sonchifolius in a greenhouse some time back and noticed its yam like tubers. Don't know how hardy it might be.

It SHOULD grow in your Zone. I've grown it here in the PNW (both 8b as well as 8a). I have a feeling it will survive with coarse but deep mulching. And, of course, you can dig up the roots, eat most, store the rest indoors, and plant them back out come early spring. It does grow in the snowy Andes.

I will try one from the grocery next spring.

This and the white flowered uvedalia are so valuable as nectar and pollen resources during the frequent midsummer heat and droughts here. Their dahlia like tubers give them this ability.

Typo- canadensis is white.