Some foxgloves have self seeded in my polytunnel, and I let them grow as they make early cut flowers. But one has gone a bit strange... Have you seen anything like this and why?

Very weird! Most likely an interesting form of fasciation. Foxgloves seem prone to that. If you search "foxglove fasciation" you'll find pictures similar to yours.

https://www.recordonline.com/s...

Thank you Zoe. I had not heard of fasciation before. I was not planning on feeding it after midnight just to be safe!

In this case It is called "Pelorism". it is the abnormal radially symmetrical (actinomorphic) flowers in a species that normally has bilaterally symmetrical (zygomorphic) flowers. Very popular mutation in orchid especially Phalaenopsis, but also in some other plant including foxgloves. The peloric flower in foxgloves usually always terminal/apex.
There are cultivar with peloric foxgloves called 'Monstrosa', some seed company sell them

Hi @bowlsfarm
There is a named seed-propagated cultivar of Digitalis purpurea called 'Monstrosa' which produces one of these flowers at the terminal of the inflorescence.
There's a picture in the database:
Foxglove (Digitalis purpurea 'Monstrosa')
I found seeds (with the same picture) at this site:
https://www.anniesannuals.com/...

Also here, showing one in magenta & one white and stating there are pink, purple, white and cream in the mix:

https://www.swallowtailgardens...

There are probably others.
Pat

lol Tofi @tofitropic posted while I was typing and reviewing and checking links.

Pat

@tofitropic Thank you so much for the clarification and correction! Very interesting.
And @Hortaholic thanks for the links.

@NMoasis Happy to discuss

Thanks all. There goes my dream of collecting the seeds and making a fortune! Oh well!

Just to give another example of the Digitalis Monstrosa, it can be found, listed underneath: Foxglove (Digitalis purpurea 'Campanulata').

At the Riverview Nursery in Robson, B,C., there would be hundreds of Foxglove volunteers every year. Once in awhile, one of them would be a Monstrosa - starting to bloom with a large blossom at the top, and then looking normal the rest of the way down the stalk. It was always so magical when it would appear, and would be viewed with delight!