Have you had a hard frost? This is the best I can offer I am afraid. Sure some one will know.

Potatoe leaves already? We only planted ours on Sunday! Sounds like frost to me, Pepperpot. Cut the black leaves off, they are dead, and mound up the row(s) so that no more leaves are showing.

Yes! Thanks, we did have a bit of light frost, thankyou both very much xxx