It's a popularity contest.
The primary entry for Water Lilies only has photos from 1 person and a single comment.
Nymphaeas (Nymphaea)
That means it's not going to rank very high when I pull the list.
Next month is Daylilies Week. We should somehow let the Daylilies people know that if they want their favorite cultivar to appear, they better make sure they've posted a photo and a comment about it to the DB!