Lake Superior has trees and American flowers (7)

I believe the answer is:

lupines

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'american flowers' is the definition.
The answer and definition can be both plants as well as being plural nouns.
Perhaps they are linked in a way I don't understand?

'lake superior has trees' is the wordplay.
'lake' becomes 'l' (geographical abbreviation).
'superior' becomes 'u' (I've seen this in other clues).
'has' says to put letters next to each other.
'trees' becomes 'pines' (pine is a kind of tree).
'l'+'u'+'pines'='LUPINES'

'and' acts as a link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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