All things that pass
Are woman's looking-glass;
They show her how her bloom must fade,
And she herself be laid
With withered roses in the shade;
With withered roses and the fallen peach,
Unlovely, out of reach
Of summer joy that was.
All things that pass
Are woman's tiring-glass;
The faded lavender is sweet,
The summer is a metaphor for pleasure and beauty, but also for time passing. Once the summer is over the flowers fade. A woman’s ‘summer’ means the end of her beauty and the beginning of her ‘decline’. 
 The use of the seasons as a metaphor for time passing is common in poetry and song. 

Passing And Glassing