Florian,
I found this article published by one of our members about this plant...
http://garden.org/ideas/view/s...
And then in the comments she came back .... Check out the comment section too.
Looks like a lot would depend on where you are...Country, State, Zone, etc. You can fill out your profile, which would then be included in your posts.
Again
to NGA!!!
Edited to add...They are both perennials.