Hello I’m Andrea Castillo and this is Seasonal, a newsletter that connects you to the Bay Area food system, one fruit and vegetable at a time. Seasonal comes out twice per month, and each post highlights the most interesting aspects of one seasonal fruit or vegetable grown and harvested around the Bay Area. Find me on Instagram at @seasonalbayarea or e-mail me at seasonal@substack.com to share your feedback and suggestions, I’d love to hear from you. If you’d like to unsubscribe, click the gray unsubscribe link at the bottom of this post.

This week, we nerd out on onions, a surprisingly resilient vegetable (available year-round).

a practical choice

Choosing what to write next for Seasonal was a creative challenge. My usual sources for inspiration are not easily accessible (nature, local grocery stores, restaurants, and farmers markets) and with so much uncertainty ahead, motivation to write was difficult to find. At the same time, the shelter-in-place order and the changes to day-to-day living have altered how I cook and store my food… in a positive way. Every scrap in the kitchen is more of a precious resource than ever before and I find that I’ve been donating less and less to the compost bucket and more and more to stocks, sauces, and the freezer. 

For this post, I kept thinking about nerding out on a practical fruit or vegetable that could last for a while. I felt like I was on a quest to find the dried bean equivalent of a fresh fruit or vegetable. I was finally inspired by something that has been a master of sheltering in place for a while now. Something that doesn’t always need refrigeration to last. Something that can easily spring back to life. Something versatile and ubiquitous. While we shelter in place for at least another three weeks, the long-lasting onion seemed like quite the appropriate vegetable to zoom in on. 

year-round freshness

Locally grown and harvested onions are available year round in the Bay Area. Even though they’re available all year, their flavors can change with the seasons—late spring and summer onions are extra sweet. Even better, certain onions last for several months when properly stored and others easily resprout and can be replanted at home.

In my mind, there are two kind of onions: varieties that have edible bulbs, and varieties that have no bulbs but have edible leaves. In the agriculture world, this distinction is more formally established by dividing onions into two categories: storage onions, and fresh onions. 

no sunlight, no bulb

Storage onions are bulbs and include common varieties such as yellow, red, or white onions. The storage onion is the type of onion that has the dry, papery skin on the outside, which protects the crunchy contents of the pungent bulb inside for a long time. This protective layer makes onions an ideal vegetable to have when buying food is a challenge. 

What I did not know is that storage onions get that papery skin after harvest and as a direct result of human intervention. I foolishly thought onions naturally grew with the dry outer layer in the ground. I learned better after befriending Emily Field, the farm manager for TERI Campus of Life in Oceanside, after we started working on a side project to help prevent thousands of pounds of mushrooms from going to waste. Emily patiently did an Onions 101 Q&A with me to explain the basics of onion farming.

When storage onions start to grow, they grow long, hollow, tasty green leaves above ground. The green leaves are like the onion’s solar panels: the more leaves, the more surface area the onion has to photosynthesize and support the eventual growth of bulbs—the onion’s equivalent of a battery. To charge that battery, onions redirect energy from growing their leaves to growing their bulbs.

Different varieties of onions need different amount of daylight to start growing bulbs. For example, “long-day” onions need 14-16 hours of daylight while “short-day” onions need 10-12 hours. These two varieties are picky. If you planted a “short-day” onion now, it may not grow a bulb because our days in the Bay Area are getting longer. If instead you planted a long-day variety, you’d likely get a beautiful bulb ready for harvest in summer. I stumbled across gardening forums where people post questions trying to figure out how to convince their onions to bulb. Pairing longitude with the right variety was key and seemed to solve the problem. That said, the Bay Area straddles the long and short day division in the West Coast. With a little bit of planning and care, either the long or short day onion varieties can be grown around here.

a dry papery defense mechanism 

Once the bulb starts sticking out of the ground, it’s almost harvest time. Onions signal they’re getting ready for harvest when the neck that attaches the leaves to the bulb begins to soften. When that neck is no longer sturdy, the leaves collapse and dry out a bit, indicating the onion is ready for harvest. After harvest, humans need to help the onion build its protective dry layers with a curing process. Farmers place the bulbs in a dry, well-ventilated area for at least a week so they can fully form that protective, papery layer. Proper curing plays a key role in prolonging the storage life of onions: the dried outer layers of the bulb act as a barrier to prevent water loss and keep out disease. If these dry layers get exposed to moisture, they weaken and leave the bulb susceptible to attacks. After curing, the onions are ready to be sold and, depending on the cultivar, can last for months when kept out of the fridge and properly stored at home.

Cured storage onions destined for Ruhlman’s French onion soup, definitely not for the dog. Skins and cut off ends will live in the freezer until there’s enough to make broth.

masters of resilient sleep

How can a nutritious vegetable last for so long without refrigeration? The short answer is: by shutting itself off! Storage onions are dormant bulbs that need to sleep to survive. 

The onion is a biennial plant, meaning that it dedicates its first year of life to growing, and its second year of life to flowering to produce seeds for the next generation. To make it to year two, onions learned to survive winters by storing energy in their bulbs. Like a battery holds charge, onion bulbs hold minerals, water, flavor compounds, plant growth regulators, and carbohydrates (i.e. sugars). When it’s time to grow again, the bulb is ready with everything it needs to support its hungry sprouts (by the way, carrots, celery, and beets are also biennials and behave similarly). 

But, as eaters, we selfishly don’t want our onion bulbs sprouting. We want them to remain in sleep mode. Part of what makes an onion tasty is all the sugar this battery has been storing. Once sprouting begins, the sprouts gobble up all the sugar and the bulb loses its sweetness. Onion sprouts taste bitter so you’re better off planting that sprouted onion or donating it to the compost bin.

What wakes a dormant onion bulb? We don’t know exactly, but there are dozens of variables at play (cultivar, curing methods, humidity, temperature, and sunlight during storing to name a few). The point is that the yellow, white, or red onion sitting in your kitchen needs to remain in hibernation mode so it can last and stay tasty. And since we are sheltering in place and limiting our grocery runs, this storage super power comes in handy. Thank you, onion bulbs!

resprout, replant, regrow, repeat

Way at the other end of the onion spectrum are the milder-tasting fresh onions. They include sweet bulbs and spring onions, as well as green onions and scallions (known as bunching onions). Green onions and scallions grow year-round, are harvested young, and are eaten fresh. So what’s the difference between a green onion and a scallion? They are nearly identical: technically, scallions (Allium fistulosum) never grow a bulb like a storage onion would and green onions (Allium cepa) are storage onions that have been harvested early, before the bulb grows. Green onions and scallions taste the same and both the green leaves and sturdier white part are delectable. 

Unlike the storage onion, green onions and scallions do not last nearly as long and need refrigeration. If there is vertical space in your fridge, storing them in a jar with enough water to cover the roots and then covering them with a bag can keep them nice and crisp for a week. Why the bag? The bag and water combination creates a high humidity environment, exactly what the green onions and scallions need to retain water and stay relatively fresh—when humidity isn’t high enough, they begin to dehydrate and spoil. If you ever wonder why some grocery stores spray fresh onions (and other fresh leafy vegetables) with a fine mist, this is part of the reason why.

What fresh onions lack in storage ability, they make up for in resilience. Since they only last for a week, it would be nice if that could be extended, right? Well, if you save the root ends, green onions and scallions can regrow in a glass of water! Other than changing the water so it’s always clear, and replanting them to a container with soil (optional, but seems nice to give the onions some nutrients), there’s not much to it. The newly replanted onions will grow and be ready in about two weeks.

How come fresh leafy onions regrow so readily? Here I thought there was an elegant survival-of-the-fittest mechanism at play. Maybe these fresh onion scraps have unique abilities to regrow in just an inch of water, driven by a desire to go to seed and reproduce. I couldn’t have been more wrong. According to Richard Smith from UC Cooperative Extension Monterey County, when we cut off the green onion or scallion ends, we’re left with a compressed stem attached to fresh roots that haven’t dried out yet, leaving us with a fully functional plant. “[When] you plant them in wet soil,” Richard explains, “they just keep growing like nothing happened.” It still seems crazy to me that you can lose 90% of yourself and function like nothing happened. But I appreciate the crazy in this mighty little scrap. As a clueless gardener, it’s encouraging to know I can grow something to feed myself. Even if it starts with a garnish.

Our fresh onion patch. I cut this spring onion where the red part ends and replanted it after 4 days in water—it is way ahead of the green onions in the background (or are those scallions? I couldn’t tell the difference)! I’ll eventually trim what I need to make scallion pancakes.

oh, the things you’ll cook

My husband was one of the inspirations for this post. The onion is his favorite vegetable and he really, really wanted to learn more about them (from me). To be fair, it didn’t take a lot of convincing. To kick it up a notch, I decided to declare the week leading up to this post Onion Week. We ate onions every single day in oh-so-many different ways. Onions are versatile vegetables and they can be used in just about anything. 

There’s no way I can compete with the zillions of onion recipes online but I did want to share some of the Onion Week standouts in case you want to celebrate it too. 

One of my favorite take-aways from Samin Nosrat’s cooking lessons is to use salt and acid to macerate onions or shallots (and other vegetables too). It’s a fun way to eat raw onions and they added sheer joy to the salads, tacos, and grain bowls we made.

I am a terrible gardener and baker and somehow I’ve done much more gardening and baking now that I’m spending tons of time at home. After re-reading parts of The Food Lab, the bunch of green onions we had in our crisper drawer was just screaming to be baked into Kenji’s buttermilk biscuits. And that’s exactly what I did. They were the first proper biscuits I had ever made and they lasted all of 20 hours. I’ll be making those again, and again. 

A few days after biscuits, I was trying to figure out what to do with the jalapeños, goat cheese, spring onions, and leftover buttermilk in the fridge. I spotted our cast iron pan and, bingo! Cornbread! So off to baking I went (again). We ate half the pan in one night.   

Our wishlist includes:

  • Francis Lam’s ginger scallion sauce to put on anything

  • Ruhlman’s French onion soup with some of the vegetable stock we’ve been making from scraps and keeping in the freezer

  • My husband and I met in Taiwan so scallion pancakes (cōngyóubǐng; 蔥油餅) are kind of a must. I’ll make them with our regrown scallions (gives me a bit of time to build up the courage to tackle these).

  • A large batch of caramelized onions to keep around for a few days and freeze for later use, perhaps in more biscuits.

quick wasted food public service announcement

If you cook with organic storage onions, hang on to those dry skins and ends, roots and all—the ends still have bits of bulb attached and the skins add a nice brown color. Freeze them in a container with other vegetable leftovers and when it gets full, throw them in a pot of water and salt to make a vegetable broth. Use that broth to make rice, farro, beans, lentils, or just about any kind of soup!

layers upon layers of knowledge

There’s so much to learn about onions, I could publish endless posts on just this one vegetable. It would be easy! I didn’t even mention leeks. Or scapes! And what about cipollini! How about the differences between red, yellow, and white onions? And why do they taste different depending on how I cut them? How come they’re bad for my dog?

Just like radishes, onions reminded me how little I know, and I’m excited to discover tons more about this vegetable. Strangely, after nerding out on just a few aspects of onions, I found a new kind of comfort in cooking with onions and in replanting them for the first time. These days, I appreciate any kind of comfort I can find, and while it may not be onions, I hope today sends some kind of comfort your way.

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Andrea Castillo is a food nerd who always wants to know the what’s, how’s, when’s, and why’s of the food she eats.