Des Higgins wrote:
It is Salicornia (various species; not sure which ones you can eat). It is
a common wild plant on salt marshes all round the coasts.
Ricky Stein eat some on one of his fish cookery programmes and that probably
resulted in vast numbers of random salt marsh plants being boiled up
all over the UK. I never realised they were cultivated as well.

The ones you can eat are called Salsoda soda or Salicornia europeaea.
It says that one should ensure to cultivate the right species ... Is it
salty if it's a coastal/marshy plant?