Jonna, I haven't checked water temps but there is a period in the dry season when they seem to slow down. The pond is in the shade then and on the windy side of the garden. That wouldn't help.
Mary, guess it depends how far you want to go with them. There are ways of heating ponds if they're sheltered from your weather.
Carolyn, I haven't come across any fragrant waterlilies, not that I've specifically looked for them. It could be worth finding out if there are any around.
We had a monsoonal burst come through in the morning so it was cooler and cloudy. The lilies stayed open until 11:45 am. The tub is about 1.5 metres diameter. There's two flowers now but 3 buds already up out of the water. Tonight, or probably tomorrow night, there'll be 5 flowers. And I noticed the bottom of the tub is carpeted with seedlings. Don't know whether it's just this one or else the white day flowerer that I've got in there as well.
