Helianthus whatchamacallit

Years ago—ten, maybe—Kate found a container or two of these fall sunflowers at a local drug store or hardware store that was selling seasonal flowers. We planted them. And every September, they burst out for a month or so of glory (unkempt glory, in our case, but that's in keeping with everything else around here).

Question is: What are they? Passers-by and neighbors have sometimes asked. We still have the little plastic stick label that came with the container. It says "Helianthus salvifolius" and continues: "Perennial sunflower with stems up to 4ft. Clusters of yellow-orange ray flowers in summer. Loves sun and warm position."

Fine, but just try to find one at your friendly local nursery. Or Google (or Bing or Yahoo!) "Helianthus salvifolius." Nothing comes back. 

What you do find if you peruse Helianthus are some very, very similar looking species. Take a look at Helianthus angustifolius, also known as swamp sunflower, for instance. Pretty darn close. Or Helianthus salicifolius, or willow-leaf sunflower. Not quite as close–the leaves on the stem really are long and willowy. 

Anyway. It's our minor front-yard botanical mystery. If any plant sleuths come across this, I'd be interested in hearing your opinion.