Plant Onion Seeds Now

Photo courtesy of Baker Creek Heirloom Seeds

Photo courtesy of Baker Creek Heirloom Seeds

With the winds whipping and a high forecast in the below zeroes again, it may seem like spring and your vegetable garden are far, far away. But actually, late January and early February are a great time to start seeds indoors – onion seeds.

Onions require a long growing season, especially those that form big bulbs for storage through next winter (OK, no one wants to think about that!). You can read all about onions, garlic, shallots and leeks and tips for growing them in the January/February issue of Northern Gardener. But for a quick primer on starting onions from seed, read on.

Why plant onions from seed? If you do not want to start onions indoors from seed, you can still grow them by buying onion sets in the spring. These are onion seedlings that you can plant directly in the garden, usually in late April or early May. Growing onions from seeds has a few advantages. First, you get more variety. Some catalogs feature many types of onions as seeds – red ones, white ones, flat ones, long ones, ones from Florence, Italy, or Texas. If you enjoy growing unusual vegetables, grow them from seeds. Also, some onion growers say that onions started from seed are less likely to have problems with disease. As with anything you grow yourself, you also know exactly how your onions were grown.

When choosing seed, make sure to order types suited to our climate. Most northern gardeners will grow “long-day” onions. These are onions that bulk up best when the sun is shining 14 hours a day or more – a perfect description of our northern Mays, Junes and Julys.  Short-day onions work well for those wanting spring onions for salads.

To grow onions from seed, you will need a set of indoor lights (usually a cheap shop light apparatus with fluorescent bulbs), soilless seed starting or potting mix, trays to grow in and the seeds. Dampen the seed starting mix so that it is moist but not overly wet, and place it in the tray. Then, scatter or place the seeds fairly thickly on top of the soilless mix. The germination rate on onions seeds varies, so be sure you have plenty there. Scatter more soilless mix on top of the seeds to just barely cover and give it a spritz of water. Cover the tray with plastic film and set in a warm spot. At the first sign of growth, remove the plastic and put the tray under the lights. For a very complete discussion of indoor seed starting, check out part 1, part 2 and part 3 of our special series on it.

When the seedlings get 4 or more inches tall, you may want to transplant them into larger pots until you can plant them outside. Generally, onions should be started 10 to 12 weeks before planting outside and a minimum of two months before the last frost date in your area.

Which are your favorite seeds to start indoors?



  1. Carol on November 16, 2019 at 5:51 am

    Your links to parts 1,2,&3 of onion growing isn’t working

    • Mary Lahr Schier on November 17, 2019 at 5:10 pm

      Thanks for letting us know, Carol. The links have been fixed!

  2. How to Make Seed Starting Mix on July 21, 2021 at 2:55 pm

    […] still too early to start seeds indoors in Minnesota, with the exception of onions, but many gardeners are thinking about their seed-starting set up. While many excellent commercial […]

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