Do you find it tricky knowing when and how to harvest onions?
What I like about onions is that they essentially tell us when they're through growing. Once you see that the stems have fallen over, it's time to turn off the water to the bed they're growing in, if possible.
At this point, you should pull them up and either leave them sitting on top of the soil surface to dry out, or take them to a sheltered location. The latter is particularly important if rain is in the forecast because you don't want them to get wet.
The goal, of course, is to let the onions dry out as much as possible so they will store for a long time. At harvesting time, you can clip off all but 3/4" of the stems.
(In my case, there were still some onions in the beds where the stems hadn't yet fallen over. I left them in place and moved the drip irrigation line away from them so they wouldn't get wet.)
Once the onions you've pulled up are completely dry, you can move them to a cool, dry location that has good ventilation.
So how long do onions keep in storage? That varies widely, depending on the variety you grow.
If you planted sweet onions, such as 'Walla Walla Sweets', they'll only keep for about a month. This means you should use them up first before starting to eat the longer-keeping varieties.
Here's the first batch of onions heading to a place to dry out.
This year, I grew 3 varieties of onions: 'Yellow Sweet Spanish', 'Sterling' and 'Copra'. Despite its name, 'Yellow Sweet Spanish' will keep for about 4 months. 'Sterling' has the potential to last 6 months in storage and 'Copra' is very impressive with an expected shelf life of 10 to 12 months! Wow. (and that's why I grew 'Copra', I might add!)
To get a feel for how long your onion varieties should last in storage, check out the guides on Dixondale Farms' website. That's where I get my onion starts each spring. If you click on a variety name, the information page will list the storage potential.
I should also mention that if you live in a northern state like I do, you should select long-day onion varieties. That's because they will develop best with our long daylight hours.
Dixondale Farms also sells onions for other parts of the country, so be sure to view their planting map to select the correct type of onion (short day, intermediate day or long day) before choosing a variety to grow.