Joan Senior was one of my first daylily purchases, and it was one of my top favorites for several years. Here in zone 8b, it thrived. It increased readily, bloomed up a storm, and was just beautiful. I couldn't imagine a prettier bloom. In the early morning it started out as a very pale yellow, turning whiter as the day went on. The evergreen foliage remained green and attractive all winter here.
Unfortunately, it was very prone to rust. I had an outbreak in March of 2021. I walked outside one morning, and all my Joan Seniors were covered with rust. I actually shed tears over this. I cut them back and treated them with Green Magic, and they did come back and bloom, but they kept getting re-infected. It broke my heart, but they were causing me too much stress, so I dug them up and got rid of them. I have replaced them with a few other near whites, supposedly with better rust resistance--I hope they are as lovely and prolific as Joan Senior was.
This picture was taken in 2020, before rust ruined my carefree gardening experience:
This one is from after the first massive outbreak, when the plants seemed to have recovered, but before subsequent rust attacks:
