"Susan" wrote
I've had a Zantedeschia aethiopica for almost 3 years. I know that these
are waterside plants that like wet soil, full sun and no frost.

I don't have a pond, so the plant is in a very large pot of all-purpose
compost, kept very moist at all times, kept in an unheated greenhouse in
winter, fertilised sparingly with general-purpose fertiliser.

Problems -- It has never flowered. Its leaves are a rather pale yellowish
green (it's never lost its leaves in winter, if that means anything).

The plant is obviously not happy, so can anyone advise on what I can do to
to bring it into flower and help its leaves turn darker green?

I don't know where you are but my neighbour has 4 clumps in her front garden
(S. facing) and they have been there for years. They get damaged by any
frost but come back again quite quickly and make a magnificent display all
summer.
My own disappeared last winter after growing in the garden for years, I
doubt it was the frost and suspect some animal (found a large hole!).
Saw some in a small garden near Middle Temple Hall in London last week and
they were in flower!

A moist sunny patch in the garden will suit them fine in the S. of the
country but don't plant them out until all chance of frost has passed.

--
Regards
Bob
In Runnymede, 17 miles West of London