In The Garden: Unknown tropical plant

Wonder if anyone can help me identify this gorgeous flowering plant... My friend lives in Colombia and tells me this one has flowered once in seven years, a single flower. He also has a second plant which now has five stems-flowers.

 

Agave attenuata.

 

I concur with saltcedar.
The common names are: lion's tail, swan's neck, or foxtail

 

Thanks a lot. Had a chance to look at a couple of picture and you two are right on the money.