Didn't notice the question about Dahlias when originally asked, sorry. I almost wish they wouldn't come back. They were back again this year, for a 3rd try, but fell over as soon as they made flowers.
This 4'o'clock (Mirabilis jalapa) is coming back to health after getting lost in too much shade at my Mom's house for a few years.
This is one of the discussions that inspired me to get a ponytail palm this summer. What's going on with peoples' fat plants?