Deep Dive: Onions

Onions are one of the most ubiquitous and universally loved vegetables around the world, and throughout the course of modern human history. Bold statement, I know, but it’s true. They’re grown in over 175 countries, their domesticated cultivation can be traced as far back as 5000 BC, and they’ve been revered for their medicinal and culinary properties by ancient and modern civilizations alike. But they’re not just tasty and good for us, they also grow and store extremely well, solidifying them as a reliable staple crop for any culture that’s embraced them. 

In terms of medicinal properties, while ancient civilizations believed they held many spiritual properties, modern science has revealed their abundance of vitamin C, nutritional fiber, and antioxidants. That means the onions that garnish our tacos and chili’s, that we caramelize for our sautes and stir fries, and that we eat nearly 13 pounds of per year (on average), are good for us too! But many vegetables bear comparable nutritional properties, what really sets onions apart is their shelf-life. Most onions are harvested and dried, a process in which the outer scales of the bulbs become dry and brittle (you’ve likely torn these off every time you’ve chopped into a new onion), which helps protect the inside from rotting (much like the dried outer skin of cured meats protects the inside of the cut). While this doesn’t provide an infinite shelf-life, it does extend it to several weeks and makes them incredibly easy to store and transport. But more on that later, let's first talk about some major varieties.

Varieties and Uses

There are hundreds of varieties of onions found all over the world, however most of them fall within a few larger categories. These categories include Yellow/Brown onions, Red/Purple Onions, White Onions, as well as several that are harvested whole while they’re still young. Each of these carry different flavor profiles, and thus, can be used for vastly different culinary purposes. Understanding some key differences can help guide you to the perfect onion for any dish!

Yellow/Brown Onions: these are typically sweeter, and, due to their high sugar content, often are the best choice for caramelization and low/medium heat sauteing.

Red/Purple Onions: these are known for their sharp, crisp flavor, and are thus often used fresh. That said, when grilled or stir fried on high heat, they can reveal a beautiful complex, sweet flavor that pairs very well with other savory foods.

White Onions: these are the most mild in flavor, are often used raw as a garnish, but, like red/purple onions, can become quite complex and sweet in flavor when cooked. 

Spring Onions and Scallions: these are harvested before they’re mature, and have a crisp, bright flavor that is perfect for garnish or pops of distinctly onion-y flavor in cooked dishes. 

Shopping Sustainably

No matter where you are in the world, and no matter what season it is, you’ll almost certainly find onions at your local grocery store or farmers market. Due to the huge variety of species, their ability to grow across many seasons and store for long periods of time, agricultural advancements that extend their growing seasons, and the interconnectedness of our national and global food systems, they’re essentially always available. That said, it’s always better to stay local if possible, and to do so, it helps to understand growing regions and the varieties that typically flourish within them.

Onions grow best in moderate-to-cool climates, as excessively hot temperatures can cause them to “bolt,” a phenomenon in which the plant begins to flower and it’s storability begins to decline. Within this moderate-to-cool climate macroregion, there are three primary zones and corresponding onion-types: Long-day, Intermediate-day, and Short-day. These zones are loosely defined by latitude, so check out the map below to see where you fall (or look up your coordinates on google!):

Image courtesy of Johnny Selected Seeds

Long-day onions are best suited for latitudes of 37-47º when the days are long, are typically planted in late-winter or early-spring, harvested in spring and summer, and are some of the best onions of longer periods of storage. Examples of long-day onions include rossa di milano, blush plants, new york early, patterson, red carpet, walla walla sweet, talon, frontier, redwing, ailsa craig, bridger, and many more

Intermediate-day onions are best suited for latitudes of 32-42º when the days are around 12-14 hours in length (though they are particularly adaptable), can be planted from early-spring to early-fall, harvested from the summer to early winter, and are often very sweet. Examples of intermediate-day onions include calbra, sierra blanca, candy, cabernet, monstrell, expression, scout, zoey and more

Short-day onions are best suited for latitudes of 25-35º when the days are short, are usually planted in the fall, and harvested in the spring. Examples of short-day onions include white castle, yellow granex, desert sunrise, madalyn, red rock, pumba, gabriella, and more!

Additionally, Spring/Green onions are typically available from March to August. So, if you’re able, shop for local onions of your region while they’re in season! Out of season, you’ll likely have to rely on the larger national/global markets. To stay as seasonal as possible and support your local growers, try and source your onions from farmers markets as often as you can!

Onion Waste

Using onions often requires discarding the butt-ends as well as the dried outer skins. These are excellent sources of flavor for stocks, and, at the very least, can serve as fuel for your home-compost! Let no bit go to waste! 

Note: if you are using a composting bin with worms, some worms will avoid the onions so it may be better to compost them seperately or #UseItUp in a stock first, before composting, to reduce the chemicals that the worms avoid. 

Additionally, many growers are finding ways to reuse onions that have been damaged or decomposed while processing. While many simply compost the waste, others at larger scales have begun exploring ways to use them as biofuel! Gills Onions Advanced Energy Recovery System is a notable example, having generated enough onion-fueled electricity to power 460 homes for a year over its 10 years of operation. So cool!

Onion Tips and Tricks

Have you experienced a burning sensation in your eyes after cutting raw onions? This is due to the release of a chemical compound that is produced by the onion as a defense mechanism from damaging cells! When cells are broken, onions release enzymes that produce aerosol sulfenic acids which irritate our eyes. Many people try to avoid this irritation by wearing glasses or goggles, but there are other ways to mitigate these effects! The first is to ensure that your knife is sharp! A dull knife will crush huge numbers of cells as you try to slice through the onion, and thus, the onion will release huge quantities of this irritant. The second, is to notice the grain of your onion, and cut along it! Cutting along the grain will reduce the number of cells you have to cut through while chopping.

While many people rightfully store their vegetables in the refrigerator to extend their shelf life, onions are a notable exception. Onions store best at cool temperatures in dry, dark areas. A perfect example would be a pantry shelf in your basement. While your refrigerator may offer cooler temperatures, it often also offers a significantly more humid environment, which can rapidly degrade onions. Every onion variety has a slightly different shelf life, but most can last between two and four weeks unscathed.

Onions are toxic to dogs, cats, guinea pigs, and many other animals, so avoid letting these animals consumer onions to the best of your ability! 

Do you have any other tips, tricks, or recommendations? Let us know in the comments!