The best I ever grew is this self-seeded specimen. It's only a few months old and growing in the border. No idea if it will survive the winter but the moral of the story seems to be - use them as hardy annuals.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/26698606@N03">peganum</a> from Henfield, England
CC BY-SA 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/peganum/15029260532/">Keckiella cordifolia</a>