In the Friar's opening soliloquy in Romeo and Juliet, what does he say about the flower that he inspects?

In Romeo and Juliet, when Friar Laurence is introduced, he is holding a basket in his hand (into which he places his medicinal herbs), and this action establishes a core aspect to his characterization and his role in the within the play. Indeed, the dual nature by which these plants an herbs can simultaneously serve as curative and poison is a key theme across the soliloquy, along with the dualistic nature of life and death, all of which are significant themes within the larger arc of Romeo and Juliet.
While inspecting the flower, he states:

"Within the infant rind of this small flower / Poison hath residence, and medicine power: / For this, being smelt, with that part cheers each part; / Being tasted, slays all senses with the heart. / Two such opposed kings encamp them still / In man as well as herbs—grace and rude will/ And where the worser is predominant, / Full soon the canker death eats up that plant."

However, these lines intertwine with larger themes within the play and within the soliloquy itself. This example illustrates a far larger pattern. Earlier, as part of that same soliloquy, he says:

"I must up-fill this osier cage of ours / With baleful weeds and precious-juiced flowers. / The earth, that's nature's mother, is her tomb; / What is her burying gave, that is her womb."

There is illustrated here a kind of dualism about life and death, poison and curative, one which is present at the heart of medicine and at the heart of nature itself. Laurence himself is well aware of this tension, and his example of the plant serves to illustrate that tension, through which the beneficial and harmful properties exist side-by-side. In so doing, he is also foreshadowing later events in the story, and the role he himself and his medicinal knowledge will play within the tragedy of Romeo and Juliet.

When we first encounter Friar Lawrence in Act II Scene iii, he's gathering herbs and flowers into a basket, with which he intends to make medicine. He makes no distinction between beautiful flowers and weeds; they're both equally effective in terms of their medicinal properties. Shakespeare is using a metaphor here; the variety of flowers picked by Friar Lawrence represents both the good and bad elements that coexist in human nature. Just after Romeo enters, Friar Lawrence inspects another flower, one that illustrates the point:

Within the infant rind of this small flower Poison hath residence and medicine power. For this, being smelt, with that part cheers each part; Being tasted, stays all senses with the heart. Two such opposèd kings encamp them still, In man as well as herbs—grace and rude will.

Inside the little flower there is both good and bad, medicine and poison. It has a lovely smell, but if you try to eat it, you'll die. There are two opposing elements in everything: human beings, as well as flowers.