Hrothgar, if you're still around: the snippet you quoted is from the following hymn which we also used for May processions:


I'll Sing A Hymn To Mary

I'll sing a hymn to Mary,
The Mother of my God,
The Virgin of all virgins,
Of David's Royal blood.
O teach me, holy Mary,
A loving song to frame,
When wicked men blaspheme thee,
To love and bless thy name.

O Lily of the Valley,
O mystic Rose what tree
Or flower, e'en the fairest,
Is half so fair as thee?
O let me, though so lowly,
Recite my Mother's fame:
When wicked men blaspheme thee,
I'll love and bless thy name.

O noble Tower of David,
Of gold and ivory,
The Ark of God's Own promise,
The Gate of Heaven to me;
To live, and not to love thee,
Would fill my soul with shame:
When wicked men blaspheme thee,
I'll love and bless thy name.

But in the crown of Mary,
There lies a wondrous gem,
As Queen of all the Angels,
Which Mary shares with them;
"No sin hath e'er defiled thee,"
So doth our faith proclaim:
When wicked men blaspheme thee,
I'll love and bless thy name.

Fr. J. Wyze 1825-1898

We only used the first three verses of those above.
I copied these words from http://www.catholictradition.org/Mary/may-queen.htm which also has sheet music for the hymn, though it's not the tune we used.