I mulch my beds heavily with grass clippings and leaf litter from my woods. This year, in addition to stepping up perennial flower and vegetable planting, I am also trying to incorporate some self-seeding annuals. Is the presence of 3-6" of mulch going to prevent self-seeding? Should I be planning to manually collect and sew seeds, or pull much back for self-seeding varieties? Is it possible for the seeds to remain viable for an extra year or two and sprout once they make their way to the soil or the mulch breaks down?
Edit: I realize this might depend on species and location. Zone 4a, western WI. At this time I am looking at the following plants for self-seeding:
flowers: pale purple coneflower, violets, lupine, wild purple clover, white wild indigo
foods: cilantro, dill, borage, lemon balm, ground cherries, strawberry spinach
In the presence of 6 inches of wood-chip mulch, my experience is that very little will successfully self-seed. I don't know whether it's the mulch, the heat, my own inattention, or something else. Last year I carefully planted a bunch of annuals, and none have come back. I thought at least the marigold, but nope.
On the other hand, as my soil improves I'm finding the soil seed bank becoming more active, as things start to pop up that I definitely didn't put there. So...maybe. I scattered spinach seeds last spring and saw nothing, but apparently one or more actually seeded because this year they're everywhere. Parsely is starting to naturalize. Dill didn't take. Cilantro didn't take. Borage didn't take. All those items are endemic in other areas of the yard, areas which are not mulched.
It is also my experience that seeds are generally viable much longer than the charts would suggest--otherwise, most plants would go extinct after a single bad season.
Zone 5b/6a, alkaline soil, 12 inches of water per year. For now the goal is a water independent urban homestead with edible landscaping and food forest.
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