Widest single flower on tree hardy in the UK?
 

Must be the heat bringing on some nonsense...

I've been growing Magnolia macrophylla for a few years. It started
flowering three years ago. This year, on a tree about 4 metres high,
there will be nine flowers. Almost half have already opened
(unfortunately they last only a couple of days at most).

What is extraordinary, and resulted in this post, is the size of each
flower. I've just measured the fifth one, and, now fully open, it is 32
- 33 cm across. They aren't strongly-scented like M. grandiflora, but
the flowers have a greater diameter (grandiflora is 20 cm or so across,
maybe 25 cm in a particularly big specimen). It is often reported that
M. macrophylla has the biggest single (longest) leaves of any tree hardy
in the UK (growing naturally. It is possible that stooled Paulownia
might have bigger leaves), but I've never seen any mention of its flower
size. It led me to wonder what is the widest single flower on a plant
hardy in the UK?

Any ideas other than this magnolia?

--

Jeff