This year, I experimented with growing veggies by sowing seeds directly in the soil much earlier than suggested, with additional protection from the elements. In years past, this is what my windowsills have looked like (this many starts at once):
I enjoyed raising all those starts at the time, but there were several constraints, including regular watering, space required, hardening off, and the time needed for transplanting. This year, I only did a few starts in the house, bought some onion sets, and the rest of the plants were directly seeded in the ground. In the past, I thought I needed a greenhouse to do this. At last I realized that the first month of growth only requires a hands' width of headspace, and I built frames 5-10" tall to create a cozy growing environment.
These Red Zeppelin onions were planted on April 7th as sets with live tops, ordered from a nursery. I planted them outdoors in the conventional way, without any protection from the cold, other than a thick layer of mulch (larch needles), or in this case the outside wall of a nearby cold frame. They were sets with green tops a few inches tall when they arrived. As you can see in the photo, they are around 8" tall now, and some are smaller.
These red globe onions were sown from seed on March 5th -- a month earlier -- inside the large frame pictured in the vegetable jail / season extension post. Prior to planting, the soil had been pre-warmed with overlapping black plastic bags laid flat. They were planted with carrots as companions. These onions now have long tops, more than 18" tall.
The plants sown directly in the ground from seed had only one month head start on the mature sets, but they have definitely surpassed the sets in both height and vigor.
This honeyboat squash plant was started in the house from seed (I only did one this year). It looked very healthy in the windowsill and I hardened it off gradually, giving it more time outdoors each day. I transplanted it into the ground last week. The one gallon pot is included in the photo for scale.
This honeyboat squash plant grew from seed sown directly in the ground when it was still quite cold out in early spring. As soon as the soil thawed, I put a seed in the ground and placed a glass bowl over it, upside down. This plant has much higher turgor pressure, making the leaves stand out erect and strong, as compared with the start from indoors, which is still limp and in a state of shock from the transplanting. This squash plant is growing in the aspen hotbed, the warmest soil in the garden with lots of rotting wood and manure. That is also where I transplanted the start from indoors.
Overall, I've seen several benefits from direct seed sowing with protection, instead of raising starts indoors. Not only does this method address all of the constraints listed above, but it also avoids transplant shock and produces vigorous plants that are already adapted to the outdoors. In addition, the frames help harness some of the heat that is likely being emitted from the underground hugelkultur. Without a frame to capture the heat as it rises, a lot of that heat is simply lost. The frames also capture solar heat. I am definitely going to repeat this experiment next year and see if the results continue to guide me toward direct seed sowing.
An additional benefit is that the frames keep the marmots off my plants. They have mowed the greens outside of the frames, but what's protected actually ends up on our table. And that's the main idea of this whole exercise!