Growing Onions

The genus Allium is one of Mother Nature’s greatest gifts to cooks all around the world. I hardly ever cook a savory dish that doesn’t contain onion, garlic, or both. Unfortunately, I’ve found alliums to be a challenge to grow. Perhaps it’s my climate. They like cool weather, but they’re also day length sensitive, so it’s not a simple matter of growing them in the winter instead, like with brassicas. You have to get the timing right so that they grow enough leaves to give themselves energy to grow a big enough bulb, and to keep them from bolting before you’ve got a good bulb.

When I was a kid, my mom used to buy onion sets and plant them all over the garden. This was mostly to repel insect pests on our other crops, because we never got a good crop of onions from these and kind of accepted that. We’d plant them at the same time as everything else, the tomatoes and green beans and squash, some time around Easter. Once the weather would start getting really warm around May or June they’d bolt, that is, send up a flower stalk. If pulled at this time we’d have a golf ball sized onion to eat. If left in the garden, they’d go to seed and die without growing any bigger.

After growing up and reading a bit, I figured out that we had been doing several things wrong, which has to do with the life cycle of the onion. Onions are biennials. In their natural state, they would spend their first spring and summer growing a lot of leaves, then when the days get shorter and colder they’d transfer that energy from leaf to bulb in order to survive the winter. Then the tops die and the bulb survives underground. Once the weather warms up again, the onion sends up a new top, but this time uses its stored food in the bulb to make as many seeds as it can. Then, like a salmon spawning, the onion dies, and the next generation spend the winter as seed to start the cycle over again next year.

Onion sets sold at the hardware store are small onion bulbs that were grown from seed and harvested previously. Therefore, when planted, as far as the onion is concerned, their time growing leaves and a bulb is over, and now it’s the second year and it’s time to grow seed. The bulb of an onion set may grow a little, but soon it decides it’s too late for that, and it had better go to seed before it dies. Now that I think of it, I’m not sure if there’s any way to convince an onion set to go back to its vegetative phase and grow bigger rather than making seeds onces it's spent some time as a dormant bulb. As far as it’s concerned, those days are over and done with.

The first time I had success growing onions was when I found a garden center selling onion plants rather than onion sets. They looked just like bunches of green onions you can get at the grocery store, though a bit dirtier and other colors besides white. They were also being sold much earlier in the year, in January and February, and that’s when you should plant them here, since unlike tomatoes or squash, onions can handle freezes just fine. That's the other trick besides planting plants rather than sets. Plant them as early as possible.

These onions grew much bigger than the sets and by late spring or early summer the tops fell over and died, signaling that it was time to harvest the onions. Not a single one sent up a flower stalk, and when I pulled them up, most of them were around tennis ball size. Still a bit on the small side, but a vast improvement over golf or ping pong ball size and allowed me to go without buying onions for a couple of months.

These onions were successful because they had not yet gone through the first part of their life cycle. They had been grown from seed during the winter and this was their first spring, so they put all their energy into growing a bulb rather than seed. If I had left them in the ground, they would have gone dormant and sat there for a few months and then sent up a flower stalk.

This year I wanted to try growing onions from seed rather than buying plants, since it’s cheaper and even more self-sufficient. Because onions don’t like hot weather, in the south one must plant the seeds really early. I planted mine in November, and I probably should have planted them in October instead. The goal was to grow plants of my own that looked like the ones that are showing up in the garden centers now, but mine are still smaller. I hope they catch up. I just planted about half of them out last weekend, and I need to plant the rest as soon as possible.

Timing is important because onions are day length sensitive. That means they use the length of daylight to time important events in their lives, rather than most vegetables which use other cues such as temperature. Once the day gets long enough, the onion will go dormant no matter how big its bulb is, and that’s it. Doesn’t matter if the bulb is softball or ping pong ball sized, it’s done. That’s also why it’s important to get onion varieties that are appropriate for your area, because the closer to the equator you are, the less variation there is in day length between the seasons. In other words, the days are shorter in the south in the summer than in the north in the summer, and the days are longer in the south in the winter than in the north in the winter. It’s recommended to grow long-day onions in the north and short-day onions in the south. Unfortunately for me, it seems there are a lot more long-day varieties than short-day out there. Oh well. Maybe some day I’ll try a long-day variety just to see what happens.

With how many onions I eat, it would be great if I could grow my own. It’s just taking a steeper learning curve than I took with a lot of other crops. Next year I’m definitely starting them earlier, October at the very latest, and I’m keeping them outside more. I had my baby onions inside the garage under the grow lights most of the time, but they’re supposed to be hardy enough to take all but the hardest freezes, so I was probably being overprotective and depriving them of the much superior natural sunlight. I could probably leave them outside most of the time here, and only bring them in on the few nights we get a very hard freeze where there’s a danger their flats might freeze all the way through.