Yup mine are quite knobbly - and pale white, have seen purple ones about are they yours? Smooth and Purple?
I love them for casseroles when the Vicar comes to tea (or the like) thery do not know they are there but next day I know where they are - great taste too mind.
Have you tried the "Chinese Artichokes" look a little like a JA but are smaller and I suppose look like a large grub, supposed to be good but not tried them.
Small holder on the Gower? Not far from me then. - well 20 miles
R