While an onion seems like a simple vegetable (usually cheap, abundant, and hardly ever the star of the show), the world of selecting, growing, storing and cooking onions is surprisingly vast. This onion guide will help you make decisions on growing or buying onions from your local grower, as well as how to store and cook with them. Whether your concern is the right flavor for a certain dish or to sustain yourself on onions all winter long, this blog will help you decide which to choose. (Giveaway…the answer is often you’ll need more than one type of onion!)

growing

Seeds, Sets or Starts

A flat of Garden City Harvest onion starts ready to be planted.

Onion sets are small dried onions grown from seed the previous year, but not allowed to mature and instead kept dormant until the following spring when they are meant to be planted. This is the easiest onion to grow for beginner gardeners but the variety of onions are limited to just yellow, red/purple, or white. Also, because onions are biennial, there is a higher chance of onion sets bolting (or going to flower) the year that you plant them. (Biennials are plants that grow over the course of two years. The first year is just roots and shoots, but in the second year, they produce flowers and seed). Onion sets and any onion that bolts will not keep in storage. Larger onion sets are typically used as green onions while smaller onion sets will form bulbs.

If you’re looking for classic, large onion bulb, we recommend that you plant onion starts or seeds. Onions take a long time to grow (90-100 days), so in our climate it’s important to start onion seeds in early March in the greenhouse or buy starts in late April from a local grower.

Planting

Here are some helpful directions from one of our favorite seed suppliers, High Mowing Organic: “Direct seed onions as soon as soil can be worked or start transplants 10-12 weeks before planting date. Sow thickly in flats or 1” cells, in singles, doubles or triples. When seedlings reach 5” trim to 1” to increase girth. Transplanting is recommended for short growing seasons [that’s Missoula!] and sweet onions. Optimal soil temperature for germination is 75-85°F.” We recommend planting starts at the end of April or early May. For more information and pictures about how to plant onion seedlings or starts, read this blog.

Onions are heavy feeders and will benefit from soil amended with compost or manure, as well as liquid fish emulsion several times throughout spring. All onions and most of their relatives (leeks and shallots) are horrible sports about weeds and don’t compete well. Make sure to start with a weed-free bed when planting your onions and keep up on the weeding, especially when the onions are small and young.

Harvesting

Onions can be harvested whenever they reach desired size, which can really vary depending on your needs or wishes. I strongly recommend that the the home gardener grows one or two varieties of storage onions and harvest/thin them as they grow. I often plant my onion starts close together in a row (1- 2 inches apart) and then plan on thinning them as they grow bigger. This way, I have skinny green onions or spring onions with my first round of thinning, then mini onions, and finally I leave 4 - 6 inches between bulbs to allow those remaining to develop into nice big bulbs for storage.

Storage onions can be harvested when tops dry up and flop over. Pull bulbs from ground and cure for 3-5 days in the field or bring into barn or greenhouse and cure for two weeks. Unlike when storing onions over the winter months for eating, curing actually requires a higher temperature between 75-80°F, which is usually easy to do in late summer!

storing

First, inspect and separate each onion bulb for soft spots, mold, or sprouting and then store the good, firm, onions in a cool dry and dark place. Onions should never be stored in plastic bags - mesh bags, paper bags or boxes that allow for air circulation are good. Those onions that you pulled out of storage, that have soft spots or have sprouted, should be eaten immediately or tossed in the compost if you can’t just cut off the bad part.

Here’s what High Mowing Organic says about storing onions, “Cool slowly, and store at steady temperatures. Rapid cooling followed by a sudden warm period might break dormancy and cause onions to sprout. Optimal storage is at near freezing temperatures at 65-70% relative humidity.”

For those of us who may not have access to optimal near-freezing temperatures, do your best by storing in the basement or crawl space and check your onions regularly. Remember to remove and eat any onions that are beginning to soften, sprout, or develop mold. For more information on storing onions and other winter veggies, read this blog.

what we grow & how to eat them

Below you’ll find the many types of onions and some of their cousins (like leeks and shallots). I’ve listed them in the order that you should eat them based on their storage length and viability. Those listed first, for example, will not store long and should be eaten first, whereas those listed at the bottom of this list could stay in a cool, dark place for up to 6 months!

Green Onions, Bunching Onions or Scallions

That’s a lot of names for the same onion plant. This is an onion where we eat both the green and white parts. They are usually the first onion to harvest and are non-bulbing. While mild, they are also flavorful and often chopped and served as a garnish for salads and soups. Varieties we grow:

Evergreen
Deep Purple

Pearl Onions or Mini Onions

These onions are just the cutest little things. They are bulbing onions that get as big as a golf ball. We grow these at our farms because they mature quickly and are one of the first bulbing onions you’ll see in your CSA. They also make a great one-person serving of onion.

Purplette - early red, harvested at golf ball size or smaller, 60 days to maturity

White wax - early white mini onion

Sweet Onions

Sweet onions have a lot of publicity and trademarked varieties based on the town name. Sweet onions are known for their mild, sweet flavor and juiciness. Becuse of their high water content, they are NOT for storage. In fact, these onions are best stored in the refridgerator.

Walla Walla - mild flavored and juicy!

White Onions

White onions have a stronger, spicier flavor and a thinner skin. They are not great for long term storage (less than one month). That said, if you leave the papery skin on, you don’t need to refrigerate them and they can sit on your counter. White onions are recommended raw in salads, salsa, guacamole, or as a garnish on tacos.

Honestly, we don’t grow a lot of white onions at Garden City Harvest, mostly out of personal farmer preference for other types. However, Samantha at the Youth Farm does and she recommends the variety White Wing.

Yellow Onions

Yellow onions are the classic onion and very versatile. They are frequently used whenever any dish calls for “an onion.” However, we don’t recommend eating yellow onions raw (of all onions, they have a high sulfur content and result in the dreaded onion breath). They are always best cooked and in fact are the preferred onion whenever we caramelize.

Yellow onions don’t need to be refrigerated and have a variety of storage lengths depending on the variety. These are the varieties that we typically grow at our farm sites, school gardens and Providence Hospital Garden.

Ailsa Craig - fresh or short term storage (1 month), mild and big sized, 110 days to maturity

Cortland - long term storage, 110 days to maturity

Dakota Tears - long term storage, open pollinated, medium - large size

Red Onions

Red onions are similar to yellow onions in being very versatile and commonly used. Red onions have more sugar content than yellow onions which is why they taste great sliced thin in salads, sandwiches, pickles or pizza. I also read that they are also the best onion to grill because they’re texture doesn’t get mushy, instead it gets jammy...(speaking of jam, one of my new favorite recipes is onion jam. Trust me, if you like crusty bread or cheese with savory toppings, you’ll love it!)

We hill the soil around the base of our leeks to keep the stalks tall, white and tender.

Cabernet - 100 days to maturity, the earliest “long day” red, medium large bulbs that will store for 4 - 6 months
Redwing - long term storage, 118 days to maturity
Red long of Tropea - not for storage, 90 days to maturity and oblong shape (mid to late summer harvest, which would be perfect for grilling in my opinion)

Cipollini

The “little onion” in Italian. They have more sugar than your average yellow or white onion so they are great roasted or carmelized. And, they store well for a sweet tasting onion (2 -3 months)! They also make great mini onions if harvested early.

Red Marble- a red cipollini that is great for storage, 75 days
Borettana - white cipollini with a very sweet flavor

Leeks

Leeks are a non-bulbing member of the garlic, onion, chive and scallion family. They have been bred to survive frosts and the winter months and are harvested in late fall. If you live somewhere without a hard freeze, some varieties overwinter and can be harvested in early spring. For a tall, slender white stalk, hill the soil around the plants at least 2 or 3 times during the summer months.

Leeks can be pretty gritty and sandy: be sure to wash carefully before cooking. The time it takes to wash a leek is well worth the effort as they melt into wonderful softness when cooked. I think they are a great compliment to potatoes, eggs, winter squash, and mushroom recipes. Some people only eat the white part of the leek, but the green part is also delicious - it just requires a longer cook time. (Tip: Heat up the oil in your pan and add the chopped green part of the leek first to give it a head start. Wait a few minutes before adding the white part of the onion.)

King Richard - open pollinated, a relatively early leek that is tall and slender (95 - 100 days), keeps in the refrigerator for a few months.

Shallots

Shallots are not an onion, but another cousin in the same big plant family. Shallots have a mild flavor, some say sweet and some say with a hint of garlic. Regardless, they lack the sharp flavor that an onion has. Shallots will store the longest of the garlic and onion family and can last until April! Many of us use shallots most often in eggs - especially frittatas! They are also recommended in many salad dressings.

Camelot - a dark red shallot with a white interior, 110 days
Glacier Rose , 98 days, large and flavorful with great storage. Available from our local seed supplier Triple Divide Seeds.
Ed’s Red, 100 days, “this shallot can get very, very big,” says Triple Divide Seeds

Onion Guide