Jan wrote:
[...]
I understand that this can happen when the bulbs are either too
congested or not deep enough. I dug up a clump to investigate, and
found lots of very small bulbs - mostly 1-1.5cm, none bigger than
2cm, and quite a lot smaller than 1cm. Most of them had grown no more
than 3 leaves. So I'm guessing congestion is the problem?

So what's the best thing to do? Do I leave them alone and hope that
they'll grow enough to flower next year, or dig them up and replant
the biggest ones, a bit more spaced out, or ditch the lot and start
again in the autumn with fresh stock?

I'd dig them all up and replant the best ones four inches apart. The
soil is probably very fertile, as you've been so generous with feeding,
so I wouldn't do anything at root level. But I wouldn't do it till the
leaves have died down in the usual way. If you want a good display next
year, though, it isn't immoral to buy in new full-sized bulbs instead --
you could do half and half.

It's even possible that your generous feeding, coupled with natural
overcrowding, has actually encouraged the bulbs to send out offsets
instead of flowering. (I don't know if this is true of daffodils: I'm
just speculating, and others here will know for sure.)

--
Mike.