Rob Barrett writes
Some of my radishes (scarlet globe) do just fine, but many develop lots
of large leaves without the root ever swelling into a radish. I've
tended to leave these, thinking the root would eventually develop, but
most don't seem to. So I eventually pull them up and compost them.
Any suggestions?

Various data: They are in full sun. The good ones and bad ones are all
growing in the same area. I have heavy clay soil that's slightly
alkaline. Located in the northeast of England. Had the same problem
last year.

Not all the radishes will develop - there always seem to be a few that
don't. But the full sun may be the problem - if they don't have enough
moisture in the soil, they abandon all ideas of storing enough food in
the roots to survive through to next year, and instead grow straight
upwards with the idea of producing seed as soon as possible.
--
Kay