Perennial foxgloves - Digitalis parviflora, ferruginia, lutea

A question for those who have grown perennial foxgloves: do they cross-pollinate?
I am growing Digitalis lutea, D. ferruginia and D. parviflora for the first time, and I'm wondering whether they're likely to self-seed, and also whether they'll come true or cross-pollinate. They will be fairly close to each other, and not far from some bog standard D. purpurea too.
Also any other tips about their quirks, preferences etc would be very welcome.
Thanks.

 

I've only grown lutea and purpurea together but did have around 50 of each. They both self seeded and I don't believe there were any signs of cross pollination. They are quite different in form and I've grown them both with grandiflora, which is somewhere in the middle of the two, and again didn't see any signs of mixing but it could have just been subtle.
Lutea for us didn't seem to last a particularly long time. It is definitely a short lived perennial and we struggled with slug damage until they were a decent size.

 

Lutea is the only one I've grown from seed myself, the others didn't germinate (though I have my doubts about he quality of the seed) so I've bought a few small plants. The lutea have been a bit slug-damaged but only one seems to have really suffered. I am not wholly against the idea of hybrids but I'd like to know if that's likely!

 

I've grown quite a number of perennial foxgloves over the years, only a few of each at any one time. Pretty much pest free, seem to last about 5 years. Not seen much self seeding, or hybridisation. D purpurea grows, dies and self seeds, both the white and purple forms.

 

I get the odd self seedling from my D. parviflora, but usually just collect and sow the seed. It is the longest lived of my Digitalis.

 

We have had disappointing results with all three. They flowered, set seeds and then we haven't seen them since. Purpurea as @NigelJ says both purple and white grow quite happily all over the garden.

 

That is rather disappointing!