Missives from a Market Farmer: Alliums—Onions and Light

Article Contributed by Judith Lessler, Durham Farmers’ Market Vendor

At the start of this series, I noted that garlic was a member of the genus, Allium. Other important members of Allium are onions, scallions, shallots, and green onions.

Classification of plants and animals into similar groups was practiced in a rudimentary form by the ancients. This endeavor is worthwhile because plants that are related share similar characteristics—such as, growth habits, flavor, and risk of poisoning. Children appear to naturally divide plants in to bitter, and, therefore, not edible and non-bitter or sweet. This is thought, by some, to enhance survival because bitter plants are more likely to be poisonous and have fewer calories. Growing children need lots of calories and are more robust if they avoid poisons. This their preference for sweet potatoes over arugula.

Traditionally plant morphology has formed the basis for grouping. Growth habit, flowering time, structure of flowers and seeds, presences of roots, bulbs, tubers, color, leaf structure, and so on are the basis for classification. Several of the articles on the genus allium note it is morphologically difficult resulting in changes over time in the nomenclature used to for the plants in the genus.

Nomenclature confusion also reigns in ordinary life. People are often confused as to differences among shallots, scallions, spring onions, and green onions, not to mention, plain old onions.  I will now clear this up for Durham Farmer’s Market customers. I am using the classification from Bon Appetit, an influential food and cooking magazine published by the famous mass media company, Conde’ Nast. Why? Because the differences are mainly important to chefs and cooks who are interested in the subtle differences in flavor of each.

  • Onions have bulbs and are sold without their leaves. They come in two types, sweet and storage. When picked, storage onions form a papery dry skin that allows them to be stored for 6 to 8 months in cool dry conditions. Sweet onions, for example, Vidalia onions do not form the dry skin but can be stored in for a couple of months if refrigerated.
  • Scallions and green onions are the same thing. They do not form bulbs and have long, hollow stems.
  • Spring onions look similar to scallions but are actually baby, bulbous onions harvested before they form the bulbs.
  • Shallots have multipart bulbs with separate cloves similar to those formed by garlic; however, these cloves do not have a thick membrane like that in garlic cloves.

Farmers must pay particular attention to one characteristic of onions, namely, whether they are short, long, or intermediate day onions. Short day onions start to form bulbs when the day-length reaches 10 to 12 hours and are grown in USDA zones 7 and higher (southern regions). Right now in our area the day length is fourteen hours and 30 minutes. We will max out at  fourteen hours and 36 minutes. To determine the longest day, one measures the number of seconds, and this usually occurs on June 20 or 21.

I love, love, love long days. So since, without looking at seconds are barely perceptible, without looking at a stop watch, I celebrate a nine day Approximate Summer Solstice. If you want to see the chart for day length by date, go to: https://sunrise-sunset.org/us/durham-nc.

Long-day onions need at day length or at least 14 hours to form bulbs. Onions grow slowly—about 110 days from planting to harvest (3.6 months). In Durham we have 2.5 months in which the days are longer than 14 hours. In Madison WI, days are longer than 14 hours for 3.5 months.

Anyway the gist is: In NC we can only grow short and intermediate day onions. Most of the short and intermediate day onions are sweet onions. For example, intermediate day onions have variety names like Candy and Red Candy Apple. Thus, onions you buy at market are likely to be sweet onions. And, since shallots are long-day Alliums, you will never be able to buy shallots from a farmers at the DFM and you can forget about the need distinguish between shallots and scallions.