Just a few notes about using the multi-plant method with a soil blocker to grow onions. Eliot Coleman recommends the multi-plant method for seeding onions, so I thought I’d give it a try. My sister gifted me some onion seed for Christmas, so I had plenty to experiment with.
Early this year I seeded both yellow and white onions into 2 inch soil blocks. I put 2-4 seeds into one soil block, and then didn’t do any thinning later. This is what they looked like right before I harvested them:
I’m not sure if you can tell, but there’s 4 onions in that bunch above. One is enormous, one is mini, and two are a medium size.
Below is a bunch of the white ones. Only 3 in this group, and they were all a similar medium size.
I don’t really have any good data about germination rates, and I didn’t do any measuring when I harvested. But in general, I feel like planting onion from seed was a success, in that I was actually able to grow and harvest a good sized crop of onions that will pretty much last us until next year. Being smashed in close together didn’t keep them from growing into normal sized onions. Putting 2-4 seeds per soil block works just fine, and saves space under the grow lights, so I plan to repeat that method next year.
Another bonus about growing onion from seed is that you get to start the seeds super early, in late January or early February, so it gives an impatient gardener something to do in a usually unproductive time of year.
Next year I will try to pay more attention to how many plants per block produces what size of an onion (and actually measure or weigh them!) so I can have some more concrete results to share with you.