In my wintersown box this year, I used origami paper pots * to separate varieties in large plastic containers.
Red russian kale so the package says. I grow different types including red ursa (my fav) and more but this is the first that I've noticed that has slightly hairy leaves at least as seedlings.
I prefer the larger, reusable plastic container rather than many smaller 'milk bottle' type because of the ease that I can move it around.
An adventurous root.
Despite my very tentative removal, the paper pot that had been sitting outside since Jan/Feb did not fall immediately apart as I feared. And though roots could go through, they were mostly contained so there was no tangling between boxes. The seedlings were still small though.
Eek, my roots are showing!
Sides were easily torn down. It probably helped that the container was moist.
These were planted out today having been well hardened off as they were never inside to begin with and the lid has been off these days with the warmer weather.
Here they are residing with some leek offsets. This is the third year going for these leeks.
The toilet rolls cut in half are cutworm collars - i.e. cutworm exclusion devices. I used to use bottomless cups but they were messy to clean up and last year, earwigs thought they made excellent nurseries.
I love winter sowing and all its variations:
* I used a slightly different technique to make the larger pots but this is instructive