Sue: (Just curious, why "small crowns"?).
I was thinking that one would remove all green bits as per the recommendation for new plants. The narrower the diameter of the remaining crown, the better prospect of the heat being conducted across all of the tissue, and not just the outer layer.
They dipped for 5 minutes. See
https://www.rhs.org.uk/advice/...
The hard part for me would be keeping the bath water evenly at the temperature for even that long.
The freezer part of our fridge is set at -19deg C which is about 13 deg F. Wouldn't that kill the mycelium but not the daylily? I would try the freezing trick in autumn some time when the plant had stopped flowering (some flower here best in our midwinter after a little rest from last bloom). I would remove all the green foliage, wrap it to try and avoid freezer burn. (Maybe it would need to be in peat or something???) Leave it there for a fortnight, then grow it inside.
I am thinking that is would be all worthwhile for when I want to give a plant to someone who doesn't have any daylilies. I don't want to start their first experience of daylilies to include rust. But I am a bit busy to try these things just yet.
