Why have my Forget me nots turned black is this normal?

This is the normal thing Jeanette. They die after flowering so you pull them up. You will find that soon you will see lots of new seedlings coming which are the new plants for next year. You will find you will have many more plants next year. In fact they try to take over. It's a good idea to move some of the new plants in September to another part of the garden where you want them, so that you only have the plants where you want them, and not too many in one place. They can overwhelm other low growing plants so that you can't see them. This has been my experience anyway.

Quite right Chris this normal as forget - me - nots are biennials [ well most are some are annuals but this confuses things ]ie grow first year flower seed and die back the second leaving new plants to germinate.Personally prefer Brunnera as produce similar flower better leaf and perennial - return each year.

Well once you've got forget - me -nots you've got them for good! I like Brunnera as well but they take up more room.
I think forget - me - nots are nice mixed up with bulbs like daffodils and tulips- especially the darker blue ones.

LoL, yes I have been try to get rid of my forget-me-nots for the last 5 years! They are nice but do need a lot of control. Too many together also encourages a fungal infection to start.

Prevent reseeding and encourage longer bloom time of existing plants by trimming spent blooms.
Then pull up and discard plants in late summer once plants have begun to whither. :-)