Starting My Onions from Seed
Time to start my onions inside my greenhouse.
Starting onions from seed isn’t difficult. They can be planted closely together in seed starting trays, and because they are shallow-rooted, they can be pulled apart easily when ready for transplanting outdoors. And by mid-summer, I'll have bounties of beautiful, flavorful, fat onions to enjoy and share.
Enjoy these photos.
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- Remember all the onions I harvested last year? It’s one of my favorite crops to pick. The onion, Allium cepa, is the most widely cultivated species of the genus Allium.
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- Onions require 90 to 100 days to mature from seed, which is around four months. I start seeding them after the New Year and then in spring they are transplanted outdoors in the garden.
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- Many of the seeds are from my favorite companies such as Baker Creek Heirloom Seed Company and Johnny’s Selected Seeds.
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- Seed starting trays come in all different sizes and depths. I use trays with shallow compartments for planting onion seeds. These are 20-row seed flats from Johnny’s Selected Seeds. They keep varieties separate and make the removal of seedlings easy for transplanting to larger celled trays or pots later.
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- Because I use a lot of onions for cooking and for sharing with my family, I plant many trays of onion seeds. My head gardener, Ryan McCallister, fills the seed starting tray with an appropriate mix.
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- It’s best to use a pre-made seed starting mix that contains the proper amounts of vermiculite, perlite and peat moss. Seed starting mixes are available at garden supply stores. I use Miracle-Gro Seed Starting Potting Mix.
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- The soil should be level with the top of the tray. Ryan fills several trays first and works in a production line process.
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- Ryan uses the edge of a wooden ruler to make quarter-inch deep furrows.
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- Here, one can see the indentations in each cell.
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- On one side of the marker he writes the vegetable variety so we can keep track of what grows well and what doesn’t.
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- On the other side, Ryan indicates what color this particular onion variety is – R for red, W for white, and Y for yellow.
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- Ryan places a marker into one of the cells, so it is clear what variety is growing in what tray.
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- Onion seeds are very small, so be sure to take time dropping them into the tray cells.
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- Slowly, Ryan drops the seeds evenly into each compartment.
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- Look closely and see the seeds in a row. It is good to start larger onions from seed, so they can be harvested the same year.
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- Once the seeds are dropped, Ryan adds an additional light layer of soil mix, so the seeds are completely covered.
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- Then he tamps down lightly to make sure there is good contact with the soil.
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- It doesn’t take long to seed several trays of onion seeds.
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- The trays are all given a good watering.
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- And then placed into my Urban Cultivator growing system – it has water, temperature and humidity all set-up in the refrigerator like unit. He covers the trays with plastic humidity domes until germination begins. Once established, the trays will be moved out into the greenhouse where they will remain until they are ready to be separated and transplanted into the ground.
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- The sprouts will be selectively thinned in a few weeks. This process eliminates the weaker sprouts and prevents overcrowding, so seedlings don’t have any competition for soil nutrients or room to mature. I hope these blogs help remind you what you can do to get ready for the next gardening season.
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