Time to get onion and leek seeds growing

Onions flowering

Sunday, February 20, 2022

Now is the time to get onion and leek seeds started indoors.  You can grow many more varieties by seed than you can get onion sets in the store.

Onion and leeks are easy to grow, have little to no pest problems and are a perennial to boot!  They will hang out in the garden until you pull them.  Onions will even multiply underground and produce "seeds" above ground.

In the Midwest, seeds can be started indoors as early as February and transplanted outdoors in March. Transplanting should be done 4-6 weeks before the last spring freeze for spring planting.  Planting later than this is also fine.

Frost date look up.

Sow up to 12 seeds in a 6" pot 1/8"- 1/2" deep, following packet instructions.  Seedlings should emerge in 6-16 days.  Onion and leeks grow best in light, loamy soils.  Apply fertilizer 1-2" below seedlings when transplanting into the garden.  When planting, space seedlings 6" apart in rows at least 12" apart.  Onions will be ready to harvest full size in 105-125 days depending on variety; leeks in 70-105 days.  Can be harvested earlier as scallions when pencil sized.

Indoor seed starting tips.

So, how do you choose which onions to plant? The best bet is to talk to your local nursery or farmers market to see which grow the best in your area for the ones that will thrive in your climate.  For leeks, you can chose a varieties that mature at different times to keep harvests for a longer time.  

If you are browsing seed catalogs for onions, you will need to know how many hours of daylight you get in the summer.  There are 3 types of bulbing onions-short day, intermediate day, and long day onions. Intermediate and long day varieties have been around for a long time.  Short day onions are relatively newcomers.

Onions are sensitive to daylight hours. They start forming bulbs when daylight hours hit a minimum. For long day onions, it is 15 hours. For intermediate, it is 12-13 hours. Intermediate, or day neutral, onions can be successfully grown anywhere.  Short day onions are 9-10 hours.

I would have thought long day onions would be for further south, but this is wrong. The north gets the really long summer days (think of Alaska in June with no darkness). Long day onions should be planted in states north of the Oklahoma/Kansas border (approximately 36 degrees latitude).

Long day onions are planted in states in the northern part of the US, intermediate in the middle and short in the South.  Short day onions are planted in the fall and form bulbs in the spring. Intermediate and long day onions are typically planted in the spring as sets, not seeds. Seeds require sprouting indoors and transplanting.

So, if you want a sweet onion and live in the Midwest, Vidalias are not the best bet since it is a short day type. Chose a long day variety if further north like Walla Walla or if you're not sure, chose Zoey or Candy day neutral varieties.  For a white onion, Superstar, Expression and Ovation are day neutral.  For a sweet, storage day neutral, try Monastrel or Red Candy Apple.  These are just a few examples of what is available.

Close up of onion flower

The other thing to keep in mind is that, like wine, onions pick up the terroir they are grown in. You can grow the exact same onion as you buy in the store or at a farmers market but have a different taste because of the differences in your soil.

There are many fun onions to grow besides the large round ones. There are the flat disk like Borrettana Cipollini yellow storage onion (long day to intermediate) or the Red Baron onion (long day) that is a red scallion type onion. Of course, there is the onion made famous in French cooking, the shallot-French, Gray or Sante are well known varieties.

Then, there are onions for keeping over the winter like Rossa Di Milano (long day), Early Yellow Globe (long day), Sweet Sandwich (long day), Hi-Keeper (day neutral), Australian Brown (day neutral) and Granex Yellow (short day, the "Vidalia" onion).

There are lots of options when starting from seed!  Chose the ones that fit with your cooking style and day light conditions.

For more on growing and harvesting onions  Everything to know about growing onions.