Onions (Allium cepa L.), being the most extensively cultivated species of the Allium genus, are a root crop that nearly everyone has heard about, seen, or eaten. However, don’t let their perceived commonness lull you into thinking they’re uninteresting. Onions are quite a fascinating garden vegetable that has some remarkable characteristics.
Onions of Olden Times
It’s thought that for well over 7,000 years the onion has been consumed or used medicinally by humans. While the first onions used were from wild sources, the cultivation of onions is thought to have started around 5,000 years ago. There’s debate on where the onion originated, some believing it first came from central Asia, while others believe it was from Iran and West Pakistan. Although the origin of the onion is debatable, the onion is known to have been used by many ancient cultures such as the Sumerians, Chinese, Egyptians, Greeks, and Romans. These cultures believed the onion had magical qualities that could be used in the afterlife, as well as healing properties to be used to treat ailments such as digestive issues, sleeplessness, poor vision, general aches and pains, and to enhance and fortify their overall health.
As the middle ages rolled around, Europeans, both rich and poor, were consuming large amounts of these vegetables. They too used them for medicinal reasons, such as to soothe and cure headaches and snakebites. Onions were even thought to have been used as gifts and payments in some areas. As the Europeans ventured to the Americas in the 17th century, they brought with them the onion. However, they found the Native Americans were already making use of the wild onions that grew there.
Past cultures saw the value the onion had to be easily grown, transported, and to provide a reliable and hardy food source. They also appreciated the onion for the magical and medicinal qualities they perceived it to possess. Even as we grow and consume this remarkable root today, we see the value it has to offer for many reasons.
This cool season vegetable is a cousin to garlic, leeks, shallots, and chives. Onions, like its cousins, are useful in companion planting with other garden plants such as beets, cabbage, strawberries, lettuce, chamomile, and even roses. The Allium genus is great at warding off harmful insects due to their pungent scent. However, just be sure not to plant them with nitrogen-fixing plants, such as legumes. Onions have antibacterial properties which are great for our health but will kill off the nitrogen-fixing bacteria and may upset the legumes and soil.
One medium onion (110 grams) offers 44 calories, 0 grams of fat, 1 gram of protein, and 10 grams of carbohydrates (2 grams of which is dietary fiber). The onion is a good source of Vitamin C and also gives us Vitamins K-1, all the B’s (except for B-12), and the minerals calcium, copper, non-heme iron, magnesium, manganese, phosphorus, potassium, selenium, and zinc. Onions also contain the flavonoid quercetin, which acts as an antioxidant. Quercetin, along with Vitamin C and the B Vitamins, help to reduce inflammation, prevent cancer, improve immunity, lower blood pressure, regulate blood glucose levels, reduce cortisol levels, and improve digestion.
Onions also contain two phytochemical compounds, allium, and allyl disulfide, that when chopped, chewed, or crushed can convert to allicin. This enzymatic activation is important because it helps our bodies eliminate cancer-causing cells, regulate insulin, and reduce possible blood vessel stiffness, which would normally lead to high blood pressure, untimely blood clotting, coronary artery disease, peripheral vascular diseases, and stroke.
Oh, the Colors!
Onions like to shake it up on the color spectrum side of things. Not satisfied coming in just one color, onions like to show up in yellows, reds, and whites. Depending on your culinary use, the color variety you choose can transform the flavors and textures of your recipes. Yellow, aka brown onions, are full-flavored and suited to routine use, working quite well in soups and stews. Red onions, sometimes called purple onions, are great when making Greek dishes, or adding color and flavor to kabobs, burgers, or salads. White onions are the more customary onion, often used for stir-fry and salsas. All these onions are typically eaten when fully mature, but can be consumed as young plants. If harvested before the bulb stage is complete, the entire onion can be used as spring onions or scallions.
Whatever the color you choose, adding onions to your garden is an easy task. All varieties and colors of onions can be grown as long as you plant them in well-drained, fertile soil that isn’t too compact. If your soil is heavy and compacted you may want to try planting your garden in raised beds or amending your soil with organic matter. Onions are best sown as soon as the ground can be worked in the spring and once temperatures no longer fall below 20°F.
Sow onions in full sun and in soil that has a high nitrogen content. Water your onions consistently as bulb size can be increased with appropriate watering, but don’t waterlog them as this can lead to rot. Consistently weed your garden to minimize competition with weeds and to keep your garden neat, tidy, and well ventilated, reducing its vulnerability to insect infestations and rot. Once you have found your spot to grow your onions and your soil is ready, you can choose to plant onion sets or transplants. Onion sets are small, dry onion bulbs that were grown the year prior and are the easier of the two to grow. In fact, all you really need to do is push the sets into moist soil until just the tops are exposed and the onions will begin to grow.
Transplants are a little trickier to grow but are more likely to yield firm, large bulbs. As you go to plant them, dig a shallow trench and place transplants along one side of the trench, 1” inch deep, and cover with soil. When spacing your onions, the size you want your bulbs to be in the end will determine how closely you plant them at the start. To yield smaller onions plant 2” apart, for an intermediate size plant 4” apart, and for large onions plant 8” apart. Trenches should be set at least 1’ foot apart from each other.
Beyond choosing to plant sets or transplants, the other choice you need to make when it comes to onion planting is the appropriate day length variety to plant. Onions are influenced by the length of days and nights, which determine if the plant will bulb, flower and set seed. Onions come in 3 daylengths, short, intermediate, and long. Onions requiring shorter daylight periods (11 to 13 hours) are called short day onions, onions requiring 13-14 hours of daylight are called intermediate, and those onions requiring the longest period of daylight (14 hours+ per day) are called long day onions.
Onions are nearly done growing when the majority of the tops lose color and fall over. Once this is observed, push down the remaining tops and allow the bulbs to rest in the ground for an additional 10-14 days to reach full maturation. Although, don’t leave for more than 14 days as this can lead to rotting later on. Do harvest your onions on a sunny day and let them sit in the sun until the roots are brittle and dry (~1 day) in order to stop any root growth. Once dry, bring the onions in and spread them out in a warm, well-ventilated space to cure. Curing should take 2-3 weeks. Be sure to turn your onions to promote full, even drying. To store onions keep them in a well-ventilated area and never place them in plastic.
After harvesting your onions, it’s time to enjoy them! As mentioned above, the variety/color of onion you grow will determine what you use it for. However, most varieties can be used interchangeably, giving the dish they are used in a unique flair with each different variety of onion used. One of my favorite things to make with onions is soup. Here’s my favorite:
French-esque Onion Soup
¼ cup butter
4 large onions- thinly sliced (any variety will do)
2 cloves garlic – crushed and minced
2-3 sprigs fresh thyme
2-3 bay leaves
6 cups chicken or beef broth
8 slices of Swiss or Gruyere Cheese
2 cups mushrooms – thinly sliced
Salt and fresh ground pepper to taste
Over medium heat melt butter in a large stock pot
Sauté onions, garlic, thyme, and bay leaves until onions begin to caramelize
Add broth, salt, and pepper
Simmer on medium-high heat for 10 minutes
Preheat oven broiler
Ladle soup into 4 ovenproof bowls, removing bay leaves at this time
Top with mushrooms and cheese
Place bowls in oven
Broil 4-5” from heat for 1-2 minutes or until cheese is melted, bubbly, and just slightly browned
Remove from oven
Allow to cool slightly
Serve and enjoy!
Boundless Onion Opportunities
The onion may be known in nearly all parts of the world, but it’s far from commonplace. It’s unique growing, harvesting, and curing style make it an interesting vegetable to add to the garden. Its array of colors, flavors, and beneficial nutritional profile make it an essential ingredient in many culinary creations. The onions you choose, and the things you can choose to do with them, are only bound by your imagination.
Choose My Plate.gov. US Department of Agriculture. SuperTracker. https://www.choosemyplate.gov/tools-supertracker
Savonen, C. July 13, 2006. Oregon State University Extension Service. Onion bulb formation is strongly linked with day length. https://extension.oregonstate.edu/gardening/onion-bulb-formation-strongly-linked-day-length
University of Maryland Extension. University of Maryland. Onions. https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/master-gardeners/Montgomery/Onion.pdf