If we're talking Nutaku, it was Cepha. But I'm talking DMM.
I was thinking it was either Canola or Di Yu.
According to DMM's last popularity poll, it is indeed Di Yu.
Well, assuming I'm reading this right...
1. Higanbana
2. Anemone
3. Pink
4. Kerria
5. Herbaceous Peony
6. Night Phlox
7. Ivy
8. Nerine
9. Chocolate Cosmos
10. Alstroemeria
11. Coral Bush
12. Setaria
13. Di Yu
14. Sakura
15. Cactus
16. Cattleya