Gary Woods wrote:

Still... you're certain that your plant is not (for example) Nelumbo lutea (the
American lotus?
Or, if it should be a hybrid... do you know which one?

I'm certain of nothing, since the plant I have was a replacement for a
poor-quality root (no growing "points" at all), and the nursery has been
unable to come up with a name.

I'm certain that the plant in the pic is Nelumbo lutea - the native
American Lotus lily. Occurring naturally as far north and west as
Iowa, it is somewhat more tolerant of winter cold than the Asian N.
nucifera, but still needs to remain unfrozen when dormant. It also
needs a fair amount of summer heat over a long period to persuade it
to do its stuff.

There are one or two growers of the nucifera hybrids in the UK who
manage to flower them out of doors in large tubs. The tubers are
overwintered indoors by draining the tubs so they rest cool but frost
free in wet soil. They are then started off in heat and moved outside
in early summer. Full sun, a warm sheltered spot and a large black
container to absorb the heat seems to be the order of the day.

I grew a few from seed some years ago - they are satisfyingly fast
growing, but need plenty of summer warmth as youngsters.
Unfortunately, I misjudged the amount of heat need early on in the
year and the young rhizomes suffered as a result. Continued cool
spring weather caused more problems and eventually they dwindled away.
I occasionally think about trying them again, but to be honest I don't
have the room to disguise large black tubs in my tiny patch.

Dave Poole
Torquay, Coastal South Devon UK
Winter min -2°C. Summer max 34°C.
Growing season: March - November