Plainsman, I hope that it is okay to drift a little off topic. I don't sow seed to overwinter greens in the garden but I wanted to comment on your selections.
I should admit to having Scotch kale that survives but it isn't made use of come spring. A few bok choy and mustard plants may
survive our sub-zero winters but no one would be interested in bringing the severely damaged plants into the kitchen. I always forget to sow spinach seed late so that the seedlings can take off early in the new growing season.
What is growing out there as tiny seedlings is Purple Orache. For about 10 years, I have left a plant in some out-of-the-way corner where it can live thru the growing season and produce seeds. It requires hard thinning come spring but the seedlings transplant well and the orache will be my first greens crop for the new year
. Orache is a spinach relative and tender enuf for use in a salad.
The Perpetual Spinach, which as you say is a beet/chard, is a good choice as a summer green. Baby beets are a favorite and I've got lots of greens of various brassicas early in the season. Perpetual Spinach is what I will have after the heat of summer takes over. Since it is a biennial, it makes little sense to expect anything from 11 or 12 month old plants other than that they are interested in going to seed. Still, sowing seed late seems like a good plan - if those plants can survive your winters.
climate information in your signature is a good thing. All gardening is local. What your neighbors are doing is most relevant to what you can expect. It is good to have you here reporting on your overwintering experiences, however. Even here, several thousand miles from your gardening, I'm expecting to learn something useful
We are each other's harvest; we are each other's business; we are each other's magnitude and bond. ~ Gwendolyn Brooks