The rules around when to use one writing method over another are a lot more fluid in practice than a textbook or classroom would have you believe, especially in casual writing. Also the names of plants and animals are frequently written in katakana even when they're native words, and especially in a scientific context.

Though, based on that second point, I'm not sure that writing ユリ for the genre would be clear, as it might tend to imply a literal lily. 🤷🏻

I've seen it used for emphasis but i could have been reading that wrong.