To expand upon that:

According to "Bert," the singer wishes his true love mildness (via parsley) to soothe the bitterness which is between them, strength (from sage) to stand firm in the time of their being apart from each other, faithfulness (through rosemary) to stay with him during this period of loneliness and paradoxically courage to fulfill her impossible tasks and to come back to him by the time she can.

This according to medieval (and earlier) beliefs about the properties of each herb.

http://www.geocities.com/paris/villa/3895/