sorry, i only came upon this site today and the thread was closed so ill post in this one.
Firstly the DEFINITIVE AND BEST version version of this song is Luke Kelly's. Van Morrison and Sinéad O' Connor? Pfaff!
A few points on the poem/song:
the queen of hearts line seems to be getting a lot of attention so my take is that while maybe a little out of place, the line has relevance- in kavanaghs eyes she was the queen of his heart, but she was making tarts, i.e uninterested or uncommited.While he was not making hay-he was preoccupied by her, while he should be doing something worthwhile-either concentrating on his work, or the country reference of making hay back in his native area.
The third verse is obviously about him trying to educate her, and in my opinion that while maybe a little condescending, it shows the depth of feeling he had, that he let her into his world.
The final verse, i think has been misconstrued a little.
"That I had wooed not as i should a creature made of clay"
I think that Kavanagh realises now that he put this woman on a pedastal, almost made a godess of her, but now he realises that she was an ordinary person "a creature made of clay", and he regrets the over-adoration of her.
Finally i think that the final line is meant to mean that kavanagh thought himself to be on a higher level to the woman (an angel) and when he wooed his lessers (the clay) he was brought back down to earth(he'd lose his wings), that he had notions at the time that were shot down due to the break up of this relationship.

Cheers and wish me luck in the leaving.
Come on Tipp!