A good, mature, flourishing plant with purple flowers (8)

I believe the answer is:

ageratum

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'plant with purple flowers' is the definition.
'ageratum' can be an answer for 'plant' (I've seen this before). I am unsure of the 'with purple flowers' bit.

'a good mature flourishing' is the wordplay.
'good' becomes 'g' (abbreviation).
'flourishing' indicates anagramming the letters (letters grow or flourish differently).
'mature' is an anagram of 'eratum'.
'a'+'g'+'eratum'='AGERATUM'

Can you help me to learn more?

(Other definitions for ageratum that I've seen before include "Plant with flowers of purple" , "growth" .)

I've seen this clue in The Independent.

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