French marigold
Refers specifically to Tagetes patula, a common garden flower.
庭にマンジュギクがたくさん咲いている。
Many French marigolds are blooming in the garden.
Usually written in katakana; the kanji form 万寿菊 is rare.
Rare kanji spelling; the katakana form is strongly preferred.
The name is a combination of 万寿 (manju, 'long life') and 菊 (kiku, 'chrysanthemum'), likely chosen for its auspicious sound and resemblance to chrysanthemums.