It’s early April and some of you might be concerned that it’s too late in the season to start your onions. You’ve noticed that most market gardeners begin their onions indoors in February, so your worry is not completely unfounded. At 20°C their onions germinate quickly and will be the thickness of a phone charger cable by April when they’re ready to be transplanted in the garden. As you read this, your onions might still be in a paper package and we’re several weeks into spring already.
There are a couple reasons why market gardeners choose to transplant their onions. First, they’re aiming for a large bulb and starting early for this one-hundred-day crop can produce a softball size storage onion.
Second, transplanting, as opposed to direct seeding, allows growers to space their onions on a grid like soldiers marching in formation resulting in uniformly sized onions. Having equally sized onions makes harvesting, cleaning, bagging, and processing much easier. This amounts to greater profits for the farmer.
But if you’re a home gardener, huge, equally sized onions isn’t crucial. In fact, your family might prefer a small onion for an omelet but a large one for the soup.
You’ll be happy to know that direct sowing onions in April will still give you sizeable bulbs for harvest in August. They won’t be enormous, but you’ll still realize a plentiful harvest. We’ve done side-by-side comparisons with direct sown onions and transplanted onions put into the ground on the same day in April. I’m always amazed by the results.
Transplanted onions, spaced six inches down the row with rows ten inches apart, produce almost identical onions with a yield only 10-20% higher than direct sown onions. Sure, for farmers growing thousands of pounds that’s a significant increase. But for home growers it’s not.
Given the ease at which onions can be seeded directly into the ground, I find this a viable option for home growers who are starting late. Onions generally have a high germination rate and if your garden soil is soft and moist, they’ll easily germinate in a couple weeks. By the end of May, a direct seeded onion, under ideal conditions, will be pencil thick.
Side dressing with rich, living compost on a weekly basis is key to giving your onions the boost they need to produce as much foliage as possible before they start putting all their energy into producing a bulb. Keep soil consistently moist during this first phase of their growth leading up the summer solstice.
Bulbing is initiated with decreasing daylength. After the longest day of the year, and especially as the leaves begin to die off towards the end of July, allow the soil to dry out slightly. By August, stop watering completely.
We typically pull up our onions and leave them to dry in the field in mid-August with the intention of drying them off completely and harvesting them before our main workforce leaves when school resumes.
If you seed your onions within the next couple weeks, they’ll spend around 120 days in the ground from seed to harvest. Most storage onions have a “days to maturity” (DTM) of 100 days (note that most seed catalogues reckon the DTM from when onions are transplanted in the ground, not from when they’re seeded).
It’s worthwhile emphasizing that gardeners who direct sow their onions in April into fertile soil will be far more successful than a gardener who transplants a healthy seedling into inferior soil around the same time. Garden fertility is all important.
So, if you’re late getting started, do everything you can to boost soil health by amending with vermicompost or living soil. Good soil is also key to increasing the storability of your onions.
My family eats an average of one onion per day. This means that I’ll need around three hundred onions to satisfy our needs. I’ll be sowing onions in my garden today, and even if they’re not as large as they could be if they’d been transplanted, I’ll be thankful to have them flavour our food in the fall and through the winter. Plus, by direct sowing onions, I save myself the needless stress associated with indoor growing.
Video: Growing Onions (6:40)
This video covers:
– When to seed & transplant (or direct plant)
– How far apart to space them
– Soil fertility & moisture tips
– Recommended variety names & characteristics
– When to harvest and how to dry them
– How to prepare & store for maximum longevity
– When to plant if you want them to over-winter (zones 6 & 7).
Some of the variety names that Dan refers to are Patterson, Walla Walla and Rossa di Milano, available from West Coast Seeds @ https://www.westcoastseeds.com/collections/onion-seeds
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