Opiate isn't made from Mexican shrub (10)

I believe the answer is:
poinsettia
'mexican shrub' is the definition.
'poinsettia' can be an answer for 'shrub' (poinsettia is a kind of shrub). I'm unsure of the 'mexican' bit.
'opiate isn't made' is the wordplay.
'made' indicates an anagram.
'opiate'+'isnt'='opiateisnt'
'opiateisnt' is an anagram of 'POINSETTIA'.
'from' is the link.
Can you help me to learn more?
(Other definitions for poinsettia that I've seen before include "American plant" , "poisonous bush" , "Flower popular at Christmas" , "bloom" , "Shrub often given at Christmas" .)
