In the famous balcony scene in act 2, scene 2, Juliet says, "What’s in a name? That which we call a rose / By any other word would smell as sweet." In other words, names, whether they're of flowers or human beings, are ultimately meaningless. Juliet is using flower imagery here to lament the absurdity of two young people, head over heels in love with each other, unable to be together because one of them is called Montague and the other Capulet.

In the following scene, Friar Lawrence is picking herbs for the strange potions and medicines he makes. He comments on their different qualities, observing how some are poisonous, whereas others are beneficial to health. Nevertheless, even the poisonous plants and herbs can be useful, so long as they're not abused.

The friar's musings foreshadow the tragic events that take place later on in the play, when Juliet will take one of his potions and fall into such a deep sleep that she will appear dead to everyone, including Romeo. Overcome with sorrow at what he thinks is Juliet's death, Romeo kills himself by taking poison. And when Juliet awakes from her drug-induced slumber and sees Romeo's dead body, she too takes her own life, stabbing herself to death with Romeo's dagger. The friar was right: there's nothing on earth that can not turn bad if it's abused. And sadly, the sleeping draught he prepared for Juliet definitely falls into that category.

*All quotes are taken from the Norton Shakespeare, based on the Oxford Edition (1997). The scenes in the Norton are off by one when compared with the eNotes text.

Act II, Scene 2 (Scene 1 in the Norton)
Capulet's garden:
The flower imagery found in this scene relates to Romeo and Juliet's budding romance--it has yet to blossom: "This bud of love by summer's ripening breath/May prove a beauteous flower when next we meet." (163-164)

Act II, Scene 3 (Scene 2 in the Norton)
Friar Lawrence's Cell
The scene opens with Friar Lawrence gathering weeds, herbs, and flowers. As he does this, he explains in detail each one; this shows his deep and thorough knowledge of the plants and their properties: "Within the infant rind of this weak flower/Poison hath residence, and medicine power,/For this, being smelt, with that part cheers each part;/Being tasted, slays all senses within the heart." (Lines 23-26)
The beginning of this scene could be an instance of foreshadowing, in that, Friar Lawrence's knowledge of plants will play a part in attempting to help Romeo and Juliet be together.