Growing native seedlings plugs & cold-stratification
Regarding growing in plugs & the cold-stratification of forbs/grasses/sedges:
I was considering buying trays of 38 plugs (20" x 10" trays), instead of open bed trays (20" x 10"s), because: 1. it will be easier to divide the seedlings for planting later on, as their lateral roots will become entwined; 2. I should have enough seed to fill 38 plugs, in most cases, and only need 24 of the 38 plugs to be successful in producing developing seedlings. Should I get a open bed trays -- having no individual plugs? The benefit of this solution would be that when I lay the trays on the ground, flushed against each other, I will not have to do as I would have to with the plug-trays; which is to make certain that the plug-trays have enough leaf mould, peat, garden soil, and perilte mix underthem... I want to make sure that the trays are embedded in substrate for moisture retention, and to give some place for the fine root hairs to travel into.
Secondly, in USDA zone 6b/7a NJ, can I sow the seeds into the trays in the fall, leave the trays on the ground (under a shade cloth shield) outside to overwinter and cover the trays with 6" of leaves, then lay and secure burlap above the leaves to make sure the leaves remain as insulation against drought and ambient air temperatures. I'm afraid that the seed would die of freezing; these are all forbs and grasses -- nothing like Asimina, Prunus, or anything that I know wouldn't do well if they freeze.
I didn't have the best success with indoor stratification because it was hard to keep the seed from rotting, without being very careful, because some of the species - those not requiring as much stratification - sprouted too early, and for possibly other unknown reasons; many species worked out, but many didn't as well. I'd like to sow outdoors this fall. I only did that because I ordered seed in winter and was concerned that sowing in winter would have shocked the seed or not allowed enough time for stratification, and that keeping the seed under refrigerated conditions would enable me to extend the winter conditions.
Should I purposely exclude species that do not require stratification (i.e. most of the native grasses I'll sow)? In the refrigerator, they germinated too early when I did that; not sure if that would happen too in late winter/early spring.
I also considered putting each species' seed in a brown paper bag (with garden soil and moistened sphagnum moss) and wrapping all these paper bags (100) in a plastic tarp and placing this in an unheated shed for the winter, protected from the wind and secure from dehydration since they are in a plastic tarp. I prefer this solution if that would work?