If you’re growing onions, we’re going to call out one of the most overlooked things about them. It comes down to genetics in northern gardens and it’s a thing you cannot miss. Most failures with onions in northern gardens are due to this fact.
Onions are sensitive to what’s called photoperiodism, a term that describes the physiological response to length of daylight. This sensitivity greatly affects the onion’s ability to “bulb out” and become the onion that we want.
Essentially, there are long day, intermediate day and short day onions. Long day onions are used in the north, where our days are quite clearly – long. Short day onions are used in places like Texas or Southern California, where they are often grown over short, cooler winter days. Intermediate varieties are often used in between, typically the highline of the US or around 50 degrees north. (Although, often these folks can also use long day type successfully too.) If you grow a short day onion in the north, it simply won’t bulb out and you’ll be left frustrated later in the season.
Some vendors are really good at identifying these characteristics. Some are not. We’ve kind of “drawn a line in the sand” and only order from vendors that do identify these characteristics with onion seeds. But, if you’re left scratching your head with a variety you have, a little bit of internet research will help you discern what type you have.
The really good news is that there are a lot of onion varieties that are considered long day type. More so than the choices our more southern growers have. So, like with a lot of things, us northerners really have it pretty good when it comes to growing choices.
Also, you won’t find onions grown from seed very often at various nurseries. While they can be found on rare occasion at boutique nurseries, they often aren’t very economical. They usually cost more for a six pack than onions actually cost in the store! The reason is that one seed equals one onion.
If you’re wanting to bypass the early sowing requirements, you can look into what are called onion sets. These are partially grown onions that are harvested very early and are then cured. These sets can be direct sowed into your garden, typically a week or two before last frost.
We’ve compared the two and honestly, there’s a reason we grow ours from seed. We see better maturity, much greater bulb size and overall healthier onion plants from seed grown. That said, we grew onion sets for many years and there’s absolutely nothing wrong with using them.
