Growing Storage Onions Part 1: Getting Ready

By Terry Phillips

How ubiquitous a vegetable. What kitchen could be without them? Chop and fry an onion and your family knows dinner is on the way, even if you don’t know yet what else is going into the pan. Visitors to your door say “that smells wonderful!” Inexpensive, easy to store, doesn’t need packaging, travels well. But oh, so hard to grow well.

My failure at growing a decent onion has been going on for a very long time. More than 30 years. I’ve tried countless varieties; from seeds, from sets, and from starts. In all types of soils and under different conditions. But something always goes wrong. So this is my attempt to figure it out and perhaps you can learn from my mistakes as I peel the layers back.

My first gardens in Victoria were planted on the traditional long weekend in May, all at once from starts or sets. Onions in crowded pots were probably happy to be in the ground, rewarding me with an instant tiny bulb. Or perhaps in cool years a few new leaves and then a tiny bulb in July.

My next gardens at Strathcona Park Lodge I learned to grow from seeds planted in Feb and March. Disease, worms, rot, and a few green stems were all that resulted. An occasional decent onion was more of a curiosity. Why did this one grow and the others didn’t?

My Quadra Island garden began in 1994. There were no improvements to onions, as I used raised beds over poor soil (loose, rocky ground) in a garden with water restrictions and a drainage rate approaching infinity.

For a few years I gave up trying to grow bulb onions and gathered some success with spring onions. (green onions, scallions, bunching onions). They filled the onion shoes for all but the winter months, where a few leeks made a stand in. And onions are cheap to buy, right?

In all my excitement this summer I planted some Walla Walla seeds in July in pots to be planted out in summer for overwintering. After transplanting the sparrows decided this new salad green was delicious. What was left the slugs finished off. We shall see if they re-sprout and grow into anything this year.

But I’ve always been interested in growing food. The more I learn about the devastation caused by mono-cropping, and the pesticides, herbicides, and fungicides sprayed on food crops (onions can get sprayed 14 times during the growing season), the more I am determined to grown my own. So I have been trying again. I learn some things, I ask questions, and I experiment. The last few years I have been able to grow a few onions. Not a lot, and not consistently, but an improvement.

So it pays to know something about onions. And then I might figure out why I failed and offer you tips. My favourite garden gurus made some unhelpful assumptions that onions were easy to grow. My favourite Brit (next to Monty Don), John Seymour of “The Self Sufficient Gardener” says, “With careful growing, harvesting and storing, there should be no part of the year in which your kitchen lacks that most indispensable ingredient, the onion.” Market gardener Eliot Coleman of “The New Organic Grower” nonchalantly grows onions from transplants in multi-plant blocks, harvesting clumps of 4-6 onions at a time. My own father shrugs at his success as if growing onions is as easy as breathing. Even my favourite seed catalogues don’t give me the special secret to a row of fat, glowing onion bulbs.

It’s complicated and multi-factorial… And not fair. I recently learned a few things from a commercial grower from England about growing onions. 1) That choosing the variety of onion for your latitude & climate is critical. 2) Your growing conditions need to be consistent. 3) That onions require food and water regularly. 4) That onions are subjected to a large number of pests and diseases, and 5) That the hobby grower is not given the same seed choices as commercial growers. Those sets you grow from? They may be rejects from the commercial growers, and they may not be the correct variety for your location and climate. (Check the label, but most just say ‘Yellow Storage Onion’ or something like that).

Bulbing: Stress, Temperature, & Day Length

Let’s take time for a deeper dive into the onion world to find out why the variety of onions needs to be specific to your latitude and climate. Four things stimulate an onion to bulb up.

First is stress. Premature heat, drought, and root restriction can all cause bulbing (and sometimes in your pots before the plants go into the ground).

Second is vernalization, a form of stress. If you have an unseasonal cold event early in your onion’s life it could cause the plant to flower early. Even storing sets at cold temperatures for too long may stimulate premature bulbing and flowering (bolting).

Third is temperature, which is why onions form bulbs in the heat of the summer. Onion leaves (tops) grow best in cool conditions like we used to have here on the coast. This tells me we need to get the most growing happening before the heat of the summer. Mulching in summer will help keep the soil cool and prevent bulbing a while longer. The more leaves your onions can put on in the growing season, the more rings they will have and theoretically, the larger they will be. Someone once told me that 13 leaves is optimum. But perhaps 7 huge leaves is better than 13 small ones.

The fourth condition that stimulates bulbing is day-length. For Canada and the northern US you must grow a ‘long-day’ onion. A long-day onion will bulb up when day length is 14 – 16 hours. (As an example, Vancouver on June 22, 2020 will have a day length of 16.24 hours). This means your onion can grow from the time you plant it until the days reach 14-16 hours. In other words, it lengthens the growing time before the onion forms a bulb. A short-day onion is encouraged to form a bulb at 12 hours. They are grown in Texas or California. Their onions are grown over the winter; planted around Halloween and forming bulbs in April when their day length is appropriately 12-13 hours, then harvested in May. In the south a long-day onion might never form a bulb. In the north a short day onion would make a bulb too early. (There are also intermediate-day onions for those places in between.)

Getting Prepared; Understanding Your Conditions

We have extremes of wet, soggy soils in the winter and hot, dry, dusty soils in the summer. You can mitigate both conditions with a good mulch. Use what you have or can get. My favourites are leaves and seaweed. But cardboard, shredded paper, straw, composted hay, grass clippings are all good. As mentioned, onions like cool growing conditions. They also like consistent moisture up until curing time, but not soggy. Recently I have switched from soaker hoses to drip tapes and am so far pleased with more even moisture. A timer keeps the water coming on regularly and can be switched off to prevent over-watering. Tops are vulnerable to damage from hail, wind, hoes or heavy mulch so take precautions when necessary.

Our soils are generally pretty poor here in the Pacific Northwest; washed with acidic rain and leaching nutrients all winter. They are generally pretty poor in organic content as well. On Quadra Island there is such a wide range of soil types; from sand, clay, peat, rock, gravel, hardpan, shoreline, and bedrock. Most of it can grow a forest, but growing vegetables requires some adjustments. Onions want the best. A good, rich soil; sandy, peaty, or silty loam will do nicely, thank you. (Two people on this island naturally have this kind of soil, I think.) What will not do is gravelly, clayey, or too sandy. Definitely not bedrock. So for the rest of us we need to do some work on our soils. Yearly additions to maintain and grow nutrition in my soil are compost, mulch and organic amendments. I am learning to prevent nutrients from leaching in the first place by using in winter a leaf or seaweed mulch. I amend every year with a good organic mixture at transplanting time. Most of our European origin vegetables thrive on less acidic soils so it is essential to add lime to most of your vegetables, including your onion bed. I add it at planting time to the transplant mix*. Sometimes I also broadcast lime in the fall or spring. Onions are shallow rooted and so get most of their nutrition in the top 4 inches of soil. They are heavy users of both calcium and magnesium, which dolomite lime provides.

Click Here for Part 2: Seeds, Starts or Sets: How Do You Decide?

Terry Phillips is a gardener on Quadra Island who has long strived to grow great onions.