This poem celebrates the scents of nature in the autumn. Characteristically Thomas uses simple language to convey the smells of dead leaves, tree roots, a bonfire to burn the detritus of the season. But it is in the last stanza that the simultaneous sadness and happiness of autumn is highlighted.
...
Today I think
Only with scents, —scents dead leaves yield,
And bracken, and wild carrot’s seed,
And the square mustard field;
Odours that rise
When the spade wounds the roots of tree,
Rose, currant, raspberry, or goutweed,
Rhubarb or celery;
The smoke’s smell, too,
Flowing from where a bonfire burns
The dead, the waste, the dangerous,
And all to sweetness turns.
It is enough
To smell, to crumble the dark earth
While the robin sings over again
Sad songs of autumn mirth.