The Ultimate Onion Guide: Grow, Harvest, Cook & Preserve

In the ultimate onion guide, you’ll find tips on growing onions, how to harvest, store and preserve them plus some of the best recipe ideas to use them.

Ultimate Onion Guide-Grow, Harvest, Cook & Preserve via An Oregon Cottage

Onions. They are truly the workhorse of the kitchen, aren’t they? I don’t think there’s a day that goes by that I don’t use them in something, actually.

While not expensive to buy and obviously easy to find, it’s still fun to grow onions.

They’re easy, don’t take up a lot of room, and can be picked at every stage between planting and harvest.

Plus, they allow me to say that I grew everything in my salsa or roasted tomato sauce, which to me is one of the best things about growing and making your own food.

So for this ultimate guide (see the other Ultimate Guides here) I’ll share some tricks I’ve learned to get the most out of your garden space, how to dry and cure them and storage ideas.

And even if you buy all your onions (and I still buy an awful lot), you’ll want to use them in the terrific preserving and cooking recipes I’ve collected below.

First, let’s talk onion varieties.

There are sweet onions like Walla Walla and Vidalia, storage onions like Stuttgart, Ebenezer or Yellow Globe, heirloom onions like Capra, bunching onions like Evergreen Hardy White, and many more (this catalog has good descriptions).

In my garden I usually grow Walla Wallas and a storage onion consistently.

Next, the seeds.

Since onion seeds are so tiny, all you need to do is lay the seeds on top of the soil and then cover lightly with compost or potting mix.

I’ve never had luck getting them to grow outdoors, though, so I start them inside (go here to see how to start plants from seeds) and then plant them out as seedlings along with onion sets I’ve purchased (sets are just small onion bulbs).

I used to only grow onions from seed and plant the seedlings. I read that this was the best way to get different varieties and have more control.

But I would have a lot failure – for some reason only about half of my seedlings would make it and I’d only get enough onions for the season but not enough to store.

When I experimented with buying onion sets, I found the red ones mostly went to seed (which can happen with sets – another reason they say to use only seedlings), but the white storage onions all grew beautifully and I finally had enough to store – they lasted until about mid-March.

So my best tip is: grow both sets AND seedlings.

Use the seedlings to grow the sweet onion variety you will eat during the growing season and the sets for the storage types.

Ultimate Onion Guide-Planting and Thinning Onions via An Oregon Cottage

How to Grow Onions

To plant seedlings (that you’ve grown yourself or bought from a nursery), dig a shallow trench and add organic fertilizer to the bottom. Mix it into the soil (even though the photos don’t show it, that’s what I do).
Carefully separate the onion seedlings and lay them out individually along your trench, spaced about 2 inches apart (purposefully close to be able to have green onions as you thin). Fill in the trench, firming the soil around the seedlings.
To plant onion sets, simply take a trowel and make a set of furrows spaced where needed (about 6″ apart in the photo). Lay the sets in all at once like pictured to see the spacing (again at 2″) before covering with dirt, firming as you go. Water all your onions well if rain isn’t expected.
One planting scheme I’ve come up with that I like is to use a long raised bed to grow onions in the spring and sunflowers in the summer. In this picture, they are growing together, but the onions mature and are harvested just as the sunflowers grow big and need the extra space.
The bed of onion sets in early July (for our Pacific NW climate, we plant in early spring). You can see that they are still too close together, even after we’ve enjoyed green onions in May and June – if left like that they wouldn’t have enough room to bulb completely. But, again, I do this on purpose to get as much out of the space as possible and now will thin again every other one.
These are the mid-season ‘thinnings’ perfect for grilled onions or any recipe.

Onions Ready to Harvest - An Oregon Cottage

How to Harvest Onions

Bulbing onions are ready to harvest when most of the tops are falling over and have begun to dry out.

Don’t wait too long, and don’t water the few weeks before harvest, if possible. Too much water causes the outer layers to rot and not store well.

Also, see the splitting bulb in the corner photo? That’s always my problem: I see a few tops laying over and I think I’ll just wait a bit to see if the bulbs will get any bigger.

Don’t do what I do – when they start to fall over, they won’t bulb anymore…but they will split.

Ultimate Onion Guitde-Drying and Storing Onions via An Oregon Cottage

How to Cure and Store Onions

If you’ve grown storage onions (and have enough to actually store), you’ll want to dry and the onions before storing. Lay them out in a single layer on cardboard or a screen in a dry, somewhat warm area like a shed or garage.
After about 2 weeks, the onion tops will have completely dried and it’s time to trim them according to how you want to keep them.
Clean off the outer layers (with just your hands) and use scissors to trim off the roots and tops to within about an inch of the top of the bulb. The onions with the thinnest necks will store the best.
Store trimmed onions in reused onion bags, putting the onions with the thinnest necks and firmest bulbs at the bottom, since they’ll last the longest. Place the bags in a cool, dry place (humidity should not be more than 70%) to help guard against mold. The temperature should not be more than 50 degrees F, or the onions may sprout.
You can also braid onions like garlic, but you’ll need to keep the tops on. Braid and secure the tops with a rubber band (which I’ve found will hold the braid as the tops dry more since it’s elastic).
After storing, make sure to check the onions regularly, using any that seem like they aren’t going to last first.