If ever you have a trip to Dublin, visit Kilmainham Jail and do the tour. You'll learn the story of this lovely song. Joseph Plunkett was arrested for taking part in the Easter rising in Dudlin 1916. On May 3rd in the evening he was allowed to marry Grace Gifford in the prison chapel. The couple were then separated. Next morning she was summoned to say goodbye to her husband of a few hours. They spoke for about ten minutes and then Joseph was executed. (shot)
The line that says " I had to leave my own sick bed" refers to the fact that Joseph was suffering from TB at the time.
The last verse mentions the blood upon the rose which was the title of a poem by Joseph which was taught in Irish Schools according to my mother!
The blood upon the rose is a reference to Christ's blood.