Hi jujo(2),
just to get the details right:
did you buy the seeds as a solid red cultivar,
or collect seeds yourself

or is it a plant grown from a tuber acting funny (which would be called a sport)?

As Dahlias ar octoploid (and always the result of muliple crossings/breeding) the plants from seed will be different from the mother plant (and each other).

those funny red-white patches look like a color pattern caused by "jumping genes", some cultivars have them, Rebecca`s world and others (which I cant`t remember the names of).

If you want to keep this color pattern, store the tubers.

Did that answer your question?

Have a nice day, bye, Lin

Here is a link that might be useful: GW-thread about

Genetically, the red and white pattern is caused by transposons and they are euphemistically called "jumping genes". The red pigment formation is interrupted by the transposon and the white pigment shows. Several named dahlia varieties have this genetic trait.

Thank you so much Lin and Ted.

those are pretty neat actually, makes me think of christmas