by Patrick Rothfuss where the protagonist is challenged by the girl he likes (heh, understatements are fun) to choose a flower that suits her. It might not help you much with your specific goal of finding "good" or "evil" flowers, but the passage sheds a lot of insight into the complexities of flower symbology, and might prove useful, especially if you want to have a morally complex magical system.
. It's one of the very few books that I recommend equally to anyone, without reservation or qualification. It is damn damn damn damn good good damn damn good good good damn good... damn. If you still would rather just read the quote, I'll include it below in spoilers.
She rolled her eyes. “Roses! I swear you men have all your romance from the same worn book. Flowers are a good thing, a sweet thing to give a lady.
But it is always roses, always red, and always perfect hothouse blooms when they can come by them.” She turned to face me. “When you see me do you think of roses?”
I knew enough to shake my head, smiling.
“What then? If not a rose what do you see?”
Trapped. I looked her up and down once, as if trying to decide. “Well,” I said slowly. “You’ll have to forgive us men. You see, it’s not an easy thing to pick a flower to fit a girl, if you’ll excuse my expression....”
She grimaced. “Pick a flower. Yes, I’ll excuse it this time.”
“The trouble is, when you gift a girl with flowers your choice can be construed so many different ways. A man might give you a rose because he feels you are beautiful, or because he fancies their shade or shape or softness similar to your lips. Roses are expensive, and perhaps he wishes to show through a valuable gift that you are valuable to him.”
“You make a good case for roses,” she said. “The fact remains I do not like them. Pick another flower to suit me.”
“But what suits? When a man gives you a rose what you see may not be what he intends. You may think he sees you as delicate or frail. Perhaps you dislike a suitor who considers you all sweet and nothing else. Perhaps the stem is thorned, and you assume he thinks you likely to hurt a hand too quick to touch. But if he trims the thorns you might think he has no liking for a thing that can defend itself with sharpness. There’s so many ways a thing can be interpreted,” I said. “What is a careful man to do?”
She cast a sidelong look to me. “If the man is you, I’d guess he would spin clever words and hope the question was forgotten.” She tilted her head. “It isn’t. What flower would you pick for me?”
“Very well, let me think.” I turned to look at her, then away. “Let’s run down a list. Dandelion might be good; it is bright, and there is a brightness about you. But dandelion is common, and you are not a common creature. Roses we have dealt with and discarded. Nightshade, no. Nettle ... perhaps.”
She made a face of mock outrage and showed me her tongue.
I tapped a finger to my lips as if reconsidering. “You are correct, except for your tongue it doesn’t suit you.”
She huffed and crossed her arms.
“Wild oat!” I exclaimed, startling a laugh from her. “It’s wildness suits you, but it is a small flower, and bashful. For that as well as other,” I cleared my throat, “more obvious reasons, I think we’ll pass the wild oat by.”
“Pity,” she said.
“Daisy is a good one,” I bulled ahead, not letting her distract me. “Tall and slender, willing to grow by roadsides. A hearty flower, not too delicate. Daisy is self-reliant. I think it might suit you.... But let us continue in our list. Iris? Too gaudy. Thistle, too distant. Violet, too brief. Trillium? Hmmm, there’s a thing. A fair flower. Doesn’t take to cultivation. The texture of the petals ...” I made the boldest motion of my young life and brushed the side of her neck gently with a pair of fingers. “... smooth enough to match your skin, just barely. But it is too close to the ground.”
“This is quite a bouquet you’ve brought for me,” she said gently. Unconsciously, she raised a hand to the side of her neck where I had touched her, held it there a moment, then let it fall.
A good sign or a bad one? Was she wiping my touch away or pressing it close? Uncertainty filled me more strongly than before and I decided to press ahead with no more blatant risks. I stopped walking. “Selas flower.”
She stopped and turned to look at me. “All this and you pick a flower I don’t know? What is a selas flower? Why?”
“It is a deep red flower that grows on a strong vine. Its leaves are dark and delicate. They grow best in shadowy places, but the flower itself finds stray sunbeams to bloom in.” I looked at her. “That suits you. There is much of you that is both shadow and light. It grows in deep forests, and is rare because only skilled folk can tend one without harming it. It has a wondrous smell and is much sought and seldom found.” I paused and made a point of examining her. “Yes, since I am forced to pick, I would choose selas.”
She looked at me. Looked away. “You think too much of me.”
I smiled. “Perhaps you think too little of yourself.”
She caught a piece of my smile and shone it back at me. “You were closer early in your list. Daisies, simple and sweet. Daisies are the way to win my heart.”
“I will remember it.” We started walking again. “What flower would you bring me?” I teased, thinking to catch her off guard.
“A willow blossom,” she said without a second’s hesitation.
I thought for a long minute. “Do willows have blossoms?”
She looked up and to the side, thinking. “I don’t think so.”
“A rare treat to be given one then.” I chuckled. “Why a willow blossom?”
“You remind me of a willow.” She said easily. “Strong, deep-rooted, and hidden. You move easily when the storm comes, but never farther than you wish.”
I lifted my hands as if fending off a blow. “Cease these sweet words,” I protested. “You seek to bend me to your will, but it will not work. Your flattery is naught to me but wind!”
She watched me for a moment, as if to make sure my tirade was complete. “Beyond all other trees,” she said with a curl of a smile on her elegant mouth, “the willow moves to the wind’s desire.”
(Ch. 62), by Patrick Rothfuss