Spruce up second half cold treat with one (5)

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

'up second half cold treat with one' is the wordplay.
'up second' becomes 'p' (2nd letter of 'up').
'half' suggests halving the letters.
'cold treat' becomes 'icepop' (I've seen this in another clue).
'with' says to put letters next to each other.
'one' becomes 'a' (a thing is one thing).
'icepop' halved is 'ice'.
'p'+'ice'+'a'='PICEA'

Can you help me to learn more?