Perennializing Onions

Onion photo.

Read this post to see how these onions grew from spring-planted sets that went to seed.

I had an interesting experience growing storage onions this year. I grow perennial onions: walking or topsetting onions and potato/multiplier onions. I also always grow typical storage onions, biennial plants that you harvest the first year or the second (if you’re planting sets).

I usually plant sets or transplants for my storage onions. I didn’t start any of my own sets or transplants this year, but found myself browsing the plant section in our local giant box home improvement store while waiting for Tree to pick up some necessary part.

It was early spring, and of course, the aisles were filled with tubs of onion sets, shallots, bulbs, rhubarb -you get the idea. It’s like going to a grocery store hungry. Pretty soon, my arms were laden with sets of red, white and yellow storage onions.

The sets went into the ground with no problem. They sprouted, grew beautifully, and then several rows started flowering. This is a danger when planting sets, you are tricking the plant into producing a bulb in its second year instead of bolting and producing a flower stalk. Remember, when a biennial flowers, that’s it. The bulb puts all of its energy into producing a woody flower stalk and not an edible onion.

Since I had so many rows of onions from my armful of sets, I wasn’t concerned about losing part of the harvest. Plus, onion flowers are beautiful, and they attract beneficial insects, so I left them as a flower border. By the end of the summer, the flowers had turned to seed and started spilling onto the garden.

By early fall, new baby onions had sprouted. They continued to sprout, and now, in mid-November, we have a variety of tiny baby onion seedlings in addition to larger scallion sized seedlings. So, that’s a natural benefit of letting onions going to seed, but something even more interesting happened (and now I’m getting to the meat of my post).

Each onion set that produced a flower stalk, multiplied into two to four more onions often with the dried stalk still in the center of the new cluster (think of the way hardneck garlic grows). So instead of acting like biennials, where the plant sets seeds and dies, these morphed into a plant similar to garlic, shallots or multiplier onions.

Onion Bulb Photo

This onion bulb grew from an onion that had gone to seed.

And the bulbs were a good size and flavorful. I made a delicious crustless quiche with carmelized onions, goat milk, goat cheese, eggs, swiss chard, fresh thyme and parmesan. Mmmm.

As for the onions, I have about a 10 foot row left. I’m pulling many, mulching some, and trying to see if I can get the seedlings to overwinter. Since these were certainly a hybrid onion, who knows what the seedlings will produce. I’ll let you know what happens in the spring. I’d love to have a multiplier onion that sets larger bulbs than potato onions.  – Jen

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1 Response to Perennializing Onions

  1. Tom Merchant says:

    Hi, what varieties were the sets? Do you think all allium cepa onions will do this (ie, leave the inedible stalk on its own surrounded by new bulbs)? I’d be interested to know because I was told letting them bolt would make them inedible, clearly untrue in your case. I’ve been doing a lot of perennialising veg in the last year or two which you might be interested in:

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