Several parts combine into one character.

花 is a phonetic-semantic compound: 艹 (the grass radical, three sprouts from soil) plus 化 (huà, "to transform / change"). The character poetically defines a flower as "the form a plant transforms into" — the moment grass becomes something more. 化 contributes both the sound (huā) and a hint of the meaning, since flowering is precisely a transformation. The 艹 radical marks nearly every plant-related character in Chinese (草 grass, 葉 leaf, 茶 tea, 薬 medicine, 菜 vegetable).

Korean reading "hwa" — clean, single-syllable. 花郞 (hwarang, "flower-youth" — the elite Silla-era youth corps that combined martial training, scholarship, and aesthetic refinement; one of the most romanticized figures in Korean history), 花壇 (hwadan, flowerbed), 開花 (gaehwa, blooming), 落花 (nakhwa, falling petals — used poetically), 無窮花 (mugunghwa, "eternal flower" = Rose of Sharon, the Korean national flower).

Mandarin huā, 1st tone. The character's meaning fanned out further in Chinese than anywhere else: 花 alone means flower, 花钱 (huā qián) = "to spend money," 花时间 (huā shíjiān) = "to spend time." The metaphor is "to scatter / disperse like petals." Modern Chinese is saturated with 花: 花朵 (huāduǒ, blossom), 花园 (huāyuán, garden), 花茶 (huāchá, flower tea), 樱花 (yīnghuā, cherry blossom). This monetary/temporal extension is uniquely Mandarin — Korean and Japanese never developed it.

Japanese on-reading カ (ka) — 開花 (kaika, blooming), 花壇 (kadan, flowerbed), 生花 (seika, ikebana / live flower arrangement). The kun-reading はな (hana) is one of the most poetic words in Japanese: 花 alone = flower; 花火 (hanabi, "flower-fire" = fireworks); 花見 (hanami, "flower-viewing" — the spring cherry blossom festival, a cornerstone of Japanese seasonal culture). When a Japanese person says 花 with no context, they typically mean 桜 (sakura, cherry blossom) — the cultural default flower.

Memory aid: grass (艹) transforming (化) — what a plant becomes when it blooms.