I received an email today from long time friend and reader, Toni, from Oregon.
I’m looking on my onion seed packets. These are seeds grown for companies locally. They all say to plant the seeds directly into the garden from April to mid-July. This is really confusing me. Do you think I should try doing that?
Because of your direction in blog posts on growing onions I first attempted to grow them. Now I LOVE growing onions.
The reason the information confused me is because I have a very significant number of onions bolt and I wonder if transplanting them is causing them to bolt?
I can understand why these instructions would be confusing.
It’s almost a guarantee — especially knowing that seeds are grown specifically for that area — 95% (or more) of gardeners will take the instructions to heart and sow directly into the garden anytime from April to mid-July. Large, wonderful onions that will cure and store for winter will be what they’ll expect as results. More than likely they’ll be disappointed.
Onions Take Growing Time Before Bulbing is Triggered
In order to get mature onions that can be cured and stored, they have to be in the garden long enough to grow large roots and tops before daylight hours and warm temperatures trigger bulbing.
Toni’s location is far enough north (Latitude 45.356507º N) that long day onions are the only ones that will do well there.
Long day onions take 14 to 16 hours of daylight (coupled with warmer temperatures) to trigger the bulbing process.
14 hours of daylight will start in her garden on the 25th of April, 2018 and gradually increase to 15 hours (her maximum amount of daylight hours) on May 18th.
Since we don’t know the variety’s exact number of hours needed to trigger bulbing , let’s assume that it’s a minimum of 14 hours which starts April 25th. If temperatures are warm enough (at least 60 to 70 degrees) bulbing will be triggered on that date.
That means the onions already need to be up and growing at least 13 weeks prior to that for the largest possible onion.
If Toni starts her onions now, her seedlings can be transplanted to the garden 6 to 8 weeks prior to the last frost date. Since that’s April 1 for her location, she’d be transplanting the seedlings February 1 to 15 for best results.
Less Leaves (Tops) When Bulbing is Triggered Means Small Onions
Following the instructions on the package and sowing directly into the garden in April will probably get good germination. But the seedlings would have less than 25 days to grow before bulbing is triggered at 14 hours of daylight on April 25th.
Even if it’s 15 hours (May 18th) that triggers that variety, seedlings would only have about 40 odd days to grow. That’s no where near enough. Bulbs would probably be dime size.
Does Transplanting Onion Seedlings Cause Bolting?
No. Transplanting seedlings does NOT cause bolting.
The normal life cycle of an onion is to grow, come to maturity, go dormant and after a period of cold resume growth and send up a seed stalk (bolting).
In short, bolting is caused by severe temperature swings that cause the onion to go dormant when it’s not suppose to. That makes it prone to bolting.
The book I’m writing on onions will go into much more detail. It’s been slow going for lots of reasons, but I think it’ll be an even better book because of it. (And, yes, I know — it seems to be taking forever!)
I want to help you as much as I can. So, if you have problems with onions, let me know what they are.
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