Moira, one guess at the meaning of "and I'll crown my love with a bunch of green": an earlier version of the song saw her fail to free her love from the gallows, and the green crown refers to his grave mound. It's often the case that an earlier, tragic version of a folk song is retold as a victory for the protagonist, but figurative language remains unchanged.

Jon W., Laurel is more likely in this context a love charm. This is its significance in English folklore