Hi Brad,

Welcome to the Oklahoma Forum and thank you so much for the kind words. We have many knowledgeable gardeners here and all of us learn so much from one another.

Onions ought to be easy to grow here, but they really aren't. Your onions are forming seedheads because they are undergoing a process known as bolting, which simply means that stress has caused them to begin setting seed. Once it starts, you can't stop it, and once the seed stalk forms, the onion usually begins to split in half, stops maturing and needs to be pulled while you can still salvage it and use it as an edible.

Onions are biennial plants and that means they grow vegetatively during their first year, undergo a period of cold-induced dormancy, and then produce seed the second year. However, cold stress at the wrong time in their growing cycle can fool them into setting seed early and that is why your plants are setting seed now.

There is very little you can do to prevent cold stress from inducing bolting in onions. Here's the key thing to remember, but since you cannot control the weather, there's still not a lot you can do. If your plants are larger in diameter than a No. 2 pencil (about 1/4") and they are exposed to temperatures below 45 degrees for about 10 to 14 days (the number of days seems to vary slightly by variety) once they are that large, they are likely to bolt. So, one prolonged cold spell can cause it, but so can the occasional cold night or two here and there. Once the cold temperatures warm up again following the cold-induced dormancy, the plants "think" it is their second year and start forming a seedstalk.

In the future, you can try to avoid this by choosing only the smallest transplants--those that are pencil-sized in diameter or smaller. The small ones still will go into cold-induced dormancy but they won't bolt. Mulching them can help by keeping the below-ground portion of the plant a little warmer. You also can grow them in a greenhouse (if you can keep it from heating up too quickly) or by growing them under a low plastic tunnel or in a cold frame. Finally, I have had better success the last couple of years (with very erratic see-sawing temperatures) by planting later than the recommended planting dates for onions in our area.

So, it is your choice as far as what to do with the bolting onions. You can remove them and use them in cooking as green onions. However, if you want and if you have the space, you can leave them in the ground and let them set seed and flower. The big balls of tiny onion flowers are very attractive to pollinators and to beneficial insects. Every year, I plant several dozen onions in my flower borders and let them bloom there to attact beneficials and pollinators. Mine are blooming now too.

There is a very fine line between planting onions "too early" or "too late". I used to always plant my onions as early as I could, but the last three years it has paid off to plant them as late as possible.....but not so late that bulbing starts before they've reached a decent size.

Dawn

Thanks, Dawn.

Since they are biennial, does that mean that if i let them seed that a fall/winter harvest is possible? Or are we talking next spring?

I will pull a few and see what they look like...can always use them and let the rest seed out.

One more question, sorry, could i seed some more onions later on for a fall harvest this year in my greenhouse or is it too late for that?

As you can tell, its my first year dealing w/ onions. LOL.

Brad

Brad,

A fall and winter onion harvest is not possible in our climate as far as I know, but George may grow an heirloom onion (Yellow of Parma) that he harvests in the fall. I can't remember if Parma is a summer harvested or fall harvested onion.

It also is possible that some modern hybrids that are daylength neutral could be grown as a fall crop, but I don't know of anyone who has done it here.

The issue is that onions are sensitive to day-length and they bulb up in response to the number of hours of sunlight they receive daily.

SHORT DAY: The short day varieties, generally grown in the southermost part of the country, begin to bulb up when sunlight begins reaching 10-11 hours daily.

INTERMEDIATE: The intermediate varieties need 12-13 hours of sunlight a day. They are grown in the far south too but do better in the middle of the country.

LONG DAY: These need 14-16 hours of sunlight a day to initiate bulbing. They are grown in the northernmost parts of the USA.

In Oklahoma, we can grown short day onions easily. In most of Oklahoma we can grown intermediate daylength onions just fine and the farther north you grow them in OK, I think the bigger the bulbs get. You probably could grow long daylength onions in northern OK, but they wouldn't get as large as intermediate and short day because their daylength needs would be only just barely met.

To further complicate it, short-day types tend to be sweet or supersweet onions which only store for a few weeks to a few months and long-day onions are hotter and more pungent but store for a long time.

So, because daylength is slowly decreasing in the summer and fall, I can't imagine how an onion would adapt.

I've never even seen anyone promote daylength-neutral onions for fall planting.

The way onions are planted in the fall in the Rio Grande Valley in south Texas is that they are planted in the fall which causes them to initiate bulbing in the spring, which is what we want. That's why our onion plants come from places in the south. It is too cold in OK most years to overwinter onions the way they do in south Texas. You might be able to do it in a climate controlled greenhouse.

In fact, here's some onion trivia: The sweet onion that many of us plant known as Texas Supersweet was sold under another name for many years: Texas 1015Y and the 1015 refers to the planting date (Oct. 15th) used in south Texas.

If you want to learn more about onions and you want to learn it from the true experts, visit the website of Dixondale Farm and check out their FAQs, Onion Growing Guide, and monthly newsletters (they always have great recipes). I've linked it below.

Dawn

Here is a link that might be useful: Dixondale Onion Farms