The flower below the step

Could not recall its name    
Now I have a choice of three.  
Before the front door it blooms    
no matter the weather.      
yesterday rain all day    
yet daisy-like it bloomed    
I brought it here    
when I leave  will stay    
flowering below the door step.    
   
   
Now spoiled for choice.   
Pyramus de Candolle named it    
 Erigeron karvinskianus    
 others    
 Mexican Fleabane    
I prefer a  third,    
 Santa Barbara Daisy    
which scans and    
has a human face.    
   
This refers to the earlier poem'Unknown'