Tamaki once tried to give Haruhi a lovely red rose.
"I don't like roses," she said, and made a little face that her 'father' deemed simply adorable. "They're much too cliché, even if they do smell nice."
Tamaki sulked for a moment before drawing himself up to his full height, raising his arms to the sky, and announcing, "Then I shall find a flower that Haruhi does like, and give her as many as she can carry!"
Haruhi snorted at his antics and hadn't taken him seriously.
He tried everything—tulips, carnations, daisies, lilies, poppies, even the rare bird of paradise that seemed to be very popular with women these days. "You'll never guess," she said each time with a mischievous little smile, or, alternatively, an airy, "Try again." The twins proudly declared that they must be rubbing off on her.
Tamaki was near tears of frustration.
Three months after his vow, he showed up to the Third Music Room with a triumphant smile and a handful of large white blossoms.
"Zinnias," he said proudly, thrusting them at a startled Haruhi. "That's my final guess—zinnias. There was a pot of them in your window."
Haruhi was too shocked to demand what Tamaki had been doing outside her window. "Yes," she squeaked, gaping at the beautiful white flowers.
He beamed. "I knew it! They're perfect for Haruhi! White zinnias mean goodness, and I think Haruhi must be the best of us all!"
White zinnias are goodness and kindness.