Here is a quick run-down on the herbs and flowers that Ophelia hands out during Act IV, scene v. She has gone crazy at this point due to the death of her father, the absence of her brother, and the treatment from her boyfriend, Hamlet.
1. Rosemary - an herb for remembrance and love. Ophelia gives this to Laertes as a symbol for their father and and his untimely death.
2. Pansies - a flower representing happy thoughts. She is also handing these to her brother as well to help him get through the horrible times he is facing.
3. Rue - an herb tied to virginity and marriage. Ophelia gives this herb to Claudius and retains one for herself. She tells him he must "wear his rue with a difference" as he is married and she is not.
4. Fennel - an herb representing those worthy of phrase, flattery, and strength. She gives these to Gertrude and to her brother. Here it appears she is allotting the traits of strength and praise to her brother, while reserving the falser trait of flattery to the Queen.
5. Columbines - this flower represents foolishness, flattery and adultery. The queen is the main recipient of this flower to symbolize her rash and foolish actions concerning both Claudius and her son.