Ok, five years too late...

This song appeared on an old record by Ewan MacColl and Peggy Seeger (I think it might be The Amorous Muse, 1968), with different words. That may be where Pentangle got it from. The thyme in the first verse signifies virginity. There is an extra verse about rue (as in 'meadow rue' ) signifying regret. I always understood the gardener's three roses to be offers of marriage at different parts of the year - the pink flowers too soon, the violet "is too deep a hue" are the words Peggy Seeger sang. I could never make out the final verse, and it's a long time since I heard it, but I think the words might also be different to the above - if I remember rightly she sings about planting something green? I couldn't decide whether the woman in the story was pregnant or not. The "If God grant me time and another year of grace" could be realistic, given the dangers of childbirth at that time?

I think this song has also been sung by Nina Simone, but with words much more like the Pentangle ones.

When I was in my prime
I flourished like a vine
There came along a false young man
Pushed away my thyme
Pushed away my thyme

My thyme it is all gone
I cannot plant anew
And in the place where grew my thyme
Is all grown up in rue
Is all grown up in rue

The gardener standing by
Three offers he made to me
The pink, the violet and red rose
But I refused all three
But I refused all three

The pink is not for me
For it flowers much too soon
The violet is too deep a hue
I said I'd wait till June
I said I'd wait till June

In June the red rose blooms
But that's no flower for me
For I've taken up my red, red rose
And planted a willow tree
And planted a willow tree

For the willow trees do twist
And the willow trees do twine
I wish I was in that young man's arms
That's won this heart of mine
That's won this heart of mine

But if God grant me time
And another year of grace
I'll plant [...]
And wash that young man's face
And wash that young man's face